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Published: 18 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.170601

Abstract:
We study the representational power of Boltzmann machines (a type of neural network) in quantum many-body systems. We prove that any (local) tensor network state has a (local) neural network representation. The construction is almost optimal in the sense that the number of parameters in the neural network representation is almost linear in the number of nonzero parameters in the tensor network representation. Despite the difficulty of representing (gapped) chiral topological states with local tensor networks, we construct a quasilocal neural network representation for a chiral $p$-wave superconductor. These results demonstrate the power of Boltzmann machines.
Alexander V. Poshakinskiy,
Published: 18 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.173601

Abstract:
We theoretically study subradiant states in an array of atoms coupled to photons propagating in a one-dimensional waveguide focusing on the strongly interacting many-body regime with large excitation fill factor $f$. We introduce a generalized many-body entropy of entanglement based on exact numerical diagonalization followed by a high-order singular value decomposition. This approach has allowed us to visualize and understand the structure of a many-body quantum state. We reveal the breakdown of fermionized subradiant states with increase of $f$ with the emergence of short-ranged dimerized antiferromagnetic correlations at the critical point $f=1/2$ and the complete disappearance of subradiant states at $f>1/2$.
Published: 18 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.177801

Abstract:
We present structural relaxation studies of a polystyrene star polymer after cessation of high-rate extensional flow. During the steady-state flow, the scattering pattern shows two sets of independent correlations peaks, reflecting the structure of a polymer confined in a fully oriented three-armed tube. Upon cessation of flow, the relaxation constitutes three distinct regimes. In a first regime, the perpendicular correlation peaks disappear, signifying disruption of the virtual tube. In a second regime, broad scattering arcs emerge, reflecting relaxation from highly aligned chains to more relaxed, still anisotropic form. New entanglements dominate the last relaxation regime where the scattering pattern evolves to a successively elliptical and circular pattern, reflecting relaxation via reptation.
, Tobias Hangleiter,
Published: 18 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.170403

Abstract:
Many qubit implementations are afflicted by correlated noise not captured by standard theoretical tools that are based on Markov approximations. While independent gate operations are a key concept for quantum computing, it is actually not possible to fully describe noisy gates locally in time if noise is correlated on times longer than their duration. To address this issue, we develop a method based on the filter function formalism to perturbatively compute quantum processes in the presence of correlated classical noise. We derive a composition rule for the filter function of a sequence of gates in terms of those of the individual gates. The joint filter function allows us to efficiently compute the quantum process of the whole sequence. Moreover, we show that correlation terms arise which capture the effects of the concatenation and, thus, yield insight into the effect of noise correlations on gate sequences. Our generalization of the filter function formalism enables both qualitative and quantitative studies of algorithms and state-of-the-art tools widely used for the experimental verification of gate fidelities like randomized benchmarking, even in the presence of noise correlations.
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.161302

Abstract:
We propose a relativistic gravitational theory leading to modified Newtonian dynamics, a paradigm that explains the observed universal galactic acceleration scale and related phenomenology. We discuss phenomenological requirements leading to its construction and demonstrate its agreement with the observed cosmic microwave background and matter power spectra on linear cosmological scales. We show that its action expanded to second order is free of ghost instabilities and discuss its possible embedding in a more fundamental theory.
, Aleksi Kurkela, , Saga Säppi,
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.162003

Abstract:
Accurate knowledge of the thermodynamic properties of zero-temperature, high-density quark matter plays an integral role in attempts to constrain the behavior of the dense QCD matter found inside neutron-star cores, irrespective of the phase realized inside the stars. In this Letter, we consider the weak-coupling expansion of the dense QCD equation of state and compute the next-to-next-to-next-to-leading-order contribution arising from the non-Abelian interactions among long-wavelength, dynamically screened gluonic fields. Accounting for these interactions requires an all-loop resummation, which can be performed using hard-thermal-loop (HTL) kinematic approximations. Concretely, we perform a full two-loop computation using the HTL effective theory, valid for the long-wavelength, or soft, modes. We find that the soft sector is well behaved within cold quark matter, contrary to the case encountered at high temperatures, and find that the new contribution decreases the renormalization-scale dependence of the equation of state at high density.
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.163902

Abstract:
We predict that photonic moiré patterns created by two mutually twisted periodic sublattices in quadratic nonlinear media allow the formation of parametric solitons under conditions that are strongly impacted by the geometry of the pattern. The question addressed here is how the geometry affects the joint trapping of multiple parametrically coupled waves into a single soliton state. We show that above the localization-delocalization transition the threshold power for soliton excitation is drastically reduced relative to uniform media. Also, the geometry of the moiré pattern shifts the condition for phase matching between the waves to the value that matches the edges of the eigenmode bands, thereby shifting the properties of all soliton families. Moreover, the phase-mismatch bandwidth for soliton generation is dramatically broadened in the moiré patterns relative to latticeless structures.
M. Fabbrichesi, R. Floreanini, G. Panizzo
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.161801

Abstract:
Correlations between the spins of top-quark pairs produced at a collider can be used to probe quantum entanglement at energies never explored so far. We show how the measurement of a single observable can provide a test of the violation of a Bell inequality at the 98% C.L. with the statistical uncertainty of the data already collected at the Large Hadron Collider, and at the 99.99% C.L. with the higher luminosity of the next run. Detector acceptance, efficiency, and migration effects are taken into account. The test relies on the spin correlations alone and does not require the determination of probabilities—in contrast to all other tests of Bell inequalities.
Sergey R. Kamaletdinov, , , Anton V. Artemyev, , Forrest Mozer
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.165101

Abstract:
We present Magnetospheric Multiscale observations showing large numbers of slow electron holes with speeds clustered near the local minimum of double-humped velocity distribution functions of background ions. Theoretical computations show that slow electron holes can avoid the acceleration that otherwise prevents their remaining slow only under these same circumstances. Although the origin of the slow electron holes is still elusive, the agreement between observation and theory about the conditions for their existence is remarkable.
, , Stoytcho S. Yazadjiev
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.161103

Abstract:
In a certain class of scalar-Gauss-Bonnet gravity, the black holes and the neutron stars can undergo spontaneous scalarization—a strong gravity phase transition triggered by a tachyonic instability due to the nonminimal coupling between the scalar field and the spacetime curvature. Studies of this phenomenon have, so far, been restricted mainly to the study of the tachyonic instability and stationary scalarized black holes and neutron stars. To date, no realistic physical mechanism for the formation of isolated scalarized black holes and neutron stars has been proposed. We study, for the first time, the spherically symmetric fully nonlinear stellar core collapse to a black hole and a neutron star in scalar-Gauss-Bonnet theories allowing for a spontaneous scalarization. We show that the core collapse can produce scalarized black holes and scalarized neutron stars starting with a nonscalarized progenitor star. The possible paths to reach the end (non)scalarized state are quite rich leading to interesting possibilities for observational manifestations.
, Yuichi Inubushi, Taito Osaka, , Kenji Tamasaku, Hitoki Yoneda,
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.163903

Abstract:
To shorten the duration of x-ray pulses, we present a nonlinear optical technique using atoms with core-hole vacancies (core-hole atoms) generated by inner-shell photoionization. The weak Coulomb screening in the core-hole atoms results in decreased absorption at photon energies immediately above the absorption edge. By employing this phenomenon, referred to as saturable absorption, we successfully reduce the duration of x-ray free-electron laser pulses (photon energy: 9.000 keV, duration: 6–7 fs, fluence: $2.0–3.5×{10}^{5}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{J}/{\mathrm{cm}}^{2}$) by $\sim 35%$. This finding that core-hole atoms are applicable to nonlinear x-ray optics is an essential stepping stone for extending nonlinear technologies commonplace at optical wavelengths to the hard x-ray region.
Mikhail Shaposhnikov, Andrey Shkerin, , Sebastian Zell
Published: 15 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.169901

Abstract:
DOI: https://doi.org/10.1103/PhysRevLett.127.169901
P. E. Garrett
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.169201

Abstract:
DOI: https://doi.org/10.1103/PhysRevLett.127.169201
Yong Yu, Peng-Fei Sun, Yu-Zhe Zhang, Bing Bai, Yu-Qiang Fang, Xi-Yu Luo, Zi-Ye An, Jun Li, , Feihu Xu, et al.
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.160502

Abstract:
In this Letter we report an experiment that verifies an atomic-ensemble quantum memory via a measurement-device-independent scheme. A single photon generated via Rydberg blockade in one atomic ensemble is stored in another atomic ensemble via electromagnetically induced transparency. After storage for a long duration, this photon is retrieved and interfered with a second photon to perform a joint Bell-state measurement (BSM). The quantum state for each photon is chosen based on a quantum random number generator, respectively, in each run. By evaluating correlations between the random states and BSM results, we certify that our memory is genuinely entanglement preserving.
Zhexin Zhao, Kenneth J. Leedle, Dylan S. Black, Olav Solgaard, Robert L. Byer, Shanhui Fan
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.164802

Abstract:
Compressing electron pulses is important in many applications of electron beam systems. In this study, we propose to use optical beat notes to compress electron pulses. The beat frequency is chosen to match the initial electron pulse duration, which enables the compression of electron pulses with a wide range of durations. This functionality extends the optical control of electron beams, which is important in compact electron beam systems such as dielectric laser accelerators. We also find that the dominant frequency of the electron charge density changes continuously along its drift trajectory, which may open up new opportunities in coherent interaction between free electrons and quantum or classical systems.
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.160501

Abstract:
We identify the large-$N$ scaling of the metrological quantum gain offered by over-squeezed spin states that are accessible by one-axis twisting, as a function of the preparation time. We further determine how the scaling is modified by relevant decoherence processes and predict a discontinuous change of the quantum gain at a critical preparation time that depends on the noise. Our analytical results provide recipes for optimal and feasible implementations of quantum enhancements with non-Gaussian spin states in existing experiments, well beyond the reach of spin squeezing.
F. Boulay, G. S. Simpson, , S. Kisyov, D. Bucurescu, A. Takamine, D. S. Ahn, K. Asahi, H. Baba, D. L. Balabanski, et al.
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.169202

Abstract:
DOI: https://doi.org/10.1103/PhysRevLett.127.169202
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166402

Abstract:
We present first principles calculations of the two-particle excitation spectrum of ${\mathrm{CrI}}_{3}$ using many-body perturbation theory including spin-orbit coupling. Specifically, we solve the Bethe-Salpeter equation, which is equivalent to summing up all ladder diagrams with static screening, and it is shown that excitons as well as magnons can be extracted seamlessly from the calculations. The resulting optical absorption spectrum as well as the magnon dispersion agree very well with recent measurements, and we extract the amplitude for optical excitation of magnons resulting from spin-orbit interactions. Importantly, the results do not rely on any assumptions of the microscopic magnetic interactions such as Dzyaloshinskii-Moriya (DM), Kitaev, or biquadratic interactions, and we obtain a model independent estimate of the gap between acoustic and optical magnons of 0.3 meV. In addition, we resolve the magnon wave function in terms of band transitions and show that the magnon carries a spin that is significantly smaller than $\hslash$. This highlights the importance of terms that do not commute with ${S}^{z}$ in any Heisenberg model description.
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.168301

Abstract:
We propose a Hamiltonian approach to reproduce the relevant elements of the centuries-old Subak irrigation system in Bali, showing a cluster-size distribution of rice-field patches that is a power-law with an exponent of $\sim 2$. Besides this exponent, the resulting system presents two equilibria. The first originates from a balance between energy and entropy contributions. The second arises from the specific energy contribution through a local Potts-type interaction in combination with a long-range antiferromagnetic interaction without attenuation. Finite-size scaling analysis shows that, as a result of the second equilibrium, the critical transition balancing energy and entropy contributions at the Potts (local ferromagnetic) regime is absorbed by the transition driven by the global-antiferromagnetic interactions, as the system size increases. The phase transition balancing energy and entropy contributions at the global-antiferromagnetic regime also shows signs of criticality. Our study extends the Hamiltonian framework to a new domain of coupled human-environmental interactions.
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.168002

Abstract:
We show that ribbed elastic strips under tension present large spontaneous curvature and may close into tubes. In this single material architectured system, transverse bending results from a bilayer effect induced by Poisson contraction as the textured ribbon is stretched. Surprisingly, the induced curvature may reverse if ribs of different orientations are considered. Slender ribbed structures may also undergo a nontrivial buckling transition. We use analytical calculations to describe the evolution of the morphology of the ribbon and the transitions between the different experimental regimes as a function of material properties, geometrical parameters, and stretching strain. This scale-independent phenomenon may help the manufacturing of tubular textured structures or easily controllable grippers at small scale.
Sami Kaappa, Casper Larsen,
Published: 14 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166001

Abstract:
We introduce a computational method for global optimization of structure and ordering in atomic systems. The method relies on interpolation between chemical elements, which is incorporated in a machine-learning structural fingerprint. The method is based on Bayesian optimization with Gaussian processes and is applied to the global optimization of Au-Cu bulk systems, Cu-Ni surfaces with CO adsorption, and Cu-Ni clusters. The method consistently identifies low-energy structures, which are likely to be the global minima of the energy. For the investigated systems with 23–66 atoms, the number of required energy and force calculations is in the range 3–75.
F. M. Gonzalez, E. M. Fries, C. Cude-Woods, T. Bailey, M. Blatnik, L. J. Broussard, N. B. Callahan, J. H. Choi, S. M. Clayton, S. A. Currie, et al.
Published: 13 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.162501

Abstract:
We report an improved measurement of the free neutron lifetime ${\tau }_{n}$ using the $\mathrm{UCN}\tau$ apparatus at the Los Alamos Neutron Science Center. We count a total of approximately $38×{10}^{6}$ surviving ultracold neutrons (UCNs) after storing in $\mathrm{UCN}\tau$’s magnetogravitational trap over two data acquisition campaigns in 2017 and 2018. We extract ${\tau }_{n}$ from three blinded, independent analyses by both pairing long and short storage time runs to find a set of replicate ${\tau }_{n}$ measurements and by performing a global likelihood fit to all data while self-consistently incorporating the $\beta$-decay lifetime. Both techniques achieve consistent results and find a value ${\tau }_{n}=877.75±0.2{8}_{\mathrm{stat}}+0.22/-0.1{6}_{\mathrm{syst}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{s}$. With this sensitivity, neutron lifetime experiments now directly address the impact of recent refinements in our understanding of the standard model for neutron decay.
, Rongchun Ge, , Mark Rudner,
Published: 13 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166804

Abstract:
We study a disordered one-dimensional fermionic system subject to quasiperiodic driving by two modes with incommensurate frequencies. We show that the system supports a topological phase in which energy is transferred between the two driving modes at a quantized rate. The phase is protected by a combination of disorder-induced spatial localization and frequency localization, a mechanism unique to quasiperiodically driven systems. We demonstrate that an analogue of the phase can be realized in a cavity-qubit system driven by two incommensurate modes.
Published: 13 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.160402

Abstract:
We show that the resource theory of contextuality does not admit catalysts, i.e., there are no correlations that can enable an otherwise impossible resource conversion and still be recovered afterward. As a corollary, we observe that the same holds for nonlocality. As entanglement allows for catalysts, this adds a further example to the list of “anomalies of entanglement,” showing that nonlocality and entanglement behave differently as resources. We also show that catalysis remains impossible even if, instead of classical randomness, we allow some more powerful behaviors to be used freely in the free transformations of the resource theory.
Xuemao Zhou, Shuo Wang, Longbin Xian, Zameer Hussain Shah, Yurou Li, ,
Published: 13 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.168001

Abstract:
We study experimentally the effect of added salt in the phoretic motion of chemically driven colloidal particles. We show that the response of passive colloids to a fixed active colloid, be it attractive or repulsive, depends on the ionic strength, the $\zeta$ potential, and the size of the passive colloids. We further report that the direction of self-propulsion of Janus colloids can be reversed by decreasing their $\zeta$ potential below a critical value. By constructing an effective model that treats the colloid and ions as a whole subjected to the concentration field of generated ions and takes into account the joint effect of both generated and background ions in determining the Debye length, we demonstrate that the response of the passive colloids and the velocity of the Janus colloids can be quantitatively captured by this model under the ionic diffusiophoresis theory beyond the infinitely-thin-double-layer limit.
Published: 13 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.161102

Abstract:
We combine adaptive template fitting and pixel count statistics in order to assess the nature of the Galactic Center excess in Fermi-LAT data. We reconstruct the flux distribution of point sources well below the Fermi-LAT detection threshold, and measure their radial and longitudinal profiles in the inner Galaxy. We find that all point sources and the bulge-correlated diffuse emission each contributes $\mathcal{O}\left(10%\right)$ of the total inner Galaxy emission, and disclose a potential subthreshold point-source contribution to the Galactic Center excess.
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.161301

Abstract:
Using Monte Carlo computer simulations, we study the impact of matter fields on the geometry of a typical quantum universe in the causal dynamical triangulations (cdt) model of lattice quantum gravity. The quantum universe has the size of a few Planck lengths and the spatial topology of a three-torus. The matter fields are multicomponent scalar fields taking values in a torus with circumference $\delta$ in each spatial direction, which acts as a new parameter in the cdt model. Changing $\delta$, we observe a phase transition caused by the scalar field. This discovery may have important consequences for quantum universes with nontrivial topology, since the phase transition can change the topology to a simply connected one.
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.165002

Abstract:
Interaction of an ultrastrong short laser pulse with nonprepolarized near-critical density plasma is investigated in an ultrarelativistic regime, with an emphasis on the radiative spin polarization of ejected electrons. Our particle-in-cell simulations show explicit correlations between the angle resolved electron polarization and the structure and properties of the transient quasistatic plasma magnetic field. While the magnitude of the spin signal is the indicator of the magnetic field strength created by the longitudinal electron current, the asymmetry of electron polarization is found to gauge the islandlike magnetic distribution which emerges due to the transverse current induced by the laser wave front. Our studies demonstrate that the spin degree of freedom of ejected electrons could potentially serve as an efficient tool to retrieve the features of strong plasma fields.
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.162002

Abstract:
The impact of the finite top-quark mass on the inclusive Higgs production cross section at higher perturbative orders has been an open question for almost three decades. In this Letter, we report on the computation of this effect at next-to-next-to-leading order QCD. For the purely gluonic channel, it amounts to $+0.62%$ relative to the result obtained in the Higgs effective field theory approximation. The formally subleading partonic channels overcompensate this shift, leading to an overall effect of $-0.26%$ at a $pp$ collider energy of 13 TeV, and $-0.1%$ at 8 TeV. This result eliminates one of the main theoretical uncertainties to inclusive Higgs production cross section at the LHC.
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.163601

Abstract:
Single photons exhibit inherently quantum and unintuitive properties such as the Hong-Ou-Mandel effect, demonstrating their bosonic and quantized nature, yet at the same time may correspond to single excitations of spatial or temporal modes with a very complex structure. Those two features are rarely seen together. Here we experimentally demonstrate how the Hong-Ou-Mandel effect can be spectrally resolved and harnessed to characterize a complex temporal mode of a single-photon—a zero-area pulse—obtained via a resonant interaction of a terahertz-bandwidth photon with a narrow gigahertz-wide atomic transition of atomic vapor. The combination of bosonic quantum behavior with bandwidth-mismatched light-atom interaction is of fundamental importance for deeper understanding of both phenomena, as well as their engineering offering applications in characterization of ultrafast transient processes.
C. Trainer, , , L. S. Farrar, , ,
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166803

Abstract:
Controlling and sensing spin polarization of electrons forms the basis of spintronics. Here, we report a study of the effect of helium on the spin polarization of the tunneling current and magnetic contrast in spin-polarized scanning tunneling microscopy (SP STM). We show that the magnetic contrast in SP STM images recorded in the presence of helium depends sensitively on the tunneling conditions. From tunneling spectra and their variation across the atomic lattice we establish that the helium can be reversibly ejected from the tunneling junction by the tunneling electrons. The energy of the tunneling electrons required to eject the helium depends on the relative spin polarization of the tip and sample, making the microscope sensitive to the magnetic exchange interactions. We show that the time-averaged spin polarization of the tunneling current is suppressed in the presence of helium and thereby demonstrate voltage control of the spin polarization of the tunneling current across the tip-sample junction.
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.161601

Abstract:
It is shown that the Ablowitz-Kaup-Newell-Segur (AKNS) integrable hierarchy can be obtained as the dynamical equations of three-dimensional general relativity with a negative cosmological constant. This geometrization of the AKNS system is possible through the construction of novel boundary conditions for the gravitational field. These are invariant under an asymptotic symmetry group characterized by an infinite set of AKNS commuting conserved charges. Gravitational configurations are studied by means of $SL\left(2,\mathbb{R}\right)$ conjugacy classes. Conical singularities and black hole solutions are included in the boundary conditions.
Rasika Dahanayake,
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.167801

Abstract:
The origin of the coil-globule transition for water-soluble thermoresponsive polymers frequently used in nanomaterials remains elusive. Using polypropylene oxide as an example we demonstrate by means of atomistic molecular dynamics simulations that temperature-induced increase in the sequence length of monomers that are not hydrogen bonded to water drives the coil-globule transition. Longer chains statistically exhibit longer sequences which serve as nucleation sites for hydrophobic cluster formation, facilitating chain collapse at lower temperature in agreement with experimental data.
, Varun Jorapur, Yuqi Zhu, Qian Wang, David DeMille
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.163201

Abstract:
We demonstrate loading of SrF molecules into an optical dipole trap (ODT) via in-trap $\mathrm{\Lambda }$-enhanced gray molasses cooling. We find that this cooling can be optimized by a proper choice of relative ODT and cooling beam polarizations. In this optimized configuration, we observe molecules with temperatures as low as $14\left(1\right)\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mu \mathrm{K}$ in traps with depths up to $570\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mu \mathrm{K}$. With optimized parameters, we transfer $\sim 5%$ of molecules from our radio-frequency magneto-optical trap into the ODT, at a density of $\sim 2×{10}^{9}\text{\hspace{0.17em}}\text{\hspace{0.17em}}{\mathrm{cm}}^{-3}$, a phase space density of $\sim 2×{10}^{-7}$, and with a trap lifetime of $\sim 1\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{s}$.
, Mikhail Lemeshko, Wojciech H. Zurek, Roman V. Krems
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.160602

Abstract:
We investigate the effect of coupling between translational and internal degrees of freedom of composite quantum particles on their localization in a random potential. We show that entanglement between the two degrees of freedom weakens localization due to the upper bound imposed on the inverse participation ratio by purity of a quantum state. We perform numerical calculations for a two-particle system bound by a harmonic force in a 1D disordered lattice and a rigid rotor in a 2D disordered lattice. We illustrate that the coupling has a dramatic effect on localization properties, even with a small number of internal states participating in quantum dynamics.
Reinis Ignatans, ,
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.167601

Abstract:
Ferroelectric materials, upon electric field biasing, display polarization discontinuities known as Barkhausen jumps, a subclass of a more general phenomenon known as crackling noise. Herein, we follow and visualize in real time the motion of single 90° needle domains induced by an electric field applied in the polarization direction of the prototypical ferroelectric ${\mathrm{BaTiO}}_{3}$, inside a transmission electron microscope. The nature of motion and periodicity of the Barkhausen pulses leads to distinctive interactions between domains forming a herringbone pattern. Remarkably, the tips of the domains do not come into contact with the body of the perpendicular domain, suggesting the presence of strong electromechanical fields around the tips of the needle domains. Additionally, interactions of the domains with the lattice result in relatively free movement of the domain walls through the dielectric medium, indicating that their motion-related activation energy depends only on weak Peierls-like potentials. Control over the kinetics of ferroelastic domain wall motion can lead to novel nanoelectronic devices pertinent to computing and data storage applications.
Jihoon Kim, Tianhong Wang, Vladimir Khudik, Gennady Shvets
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.164801

Abstract:
We demonstrate that a long-propagating plasma bubble executing undulatory motion can be produced in the wake of two copropagating laser pulses: a near-single-cycle injector and a multicycle driver. When the undulation amplitude exceeds the analytically derived threshold, highly localized injections of plasma electrons into the bubble are followed by their long-distance acceleration. While the locations of the injection regions are controlled by the carrier-envelope phase (CEP) of the injector pulse, the monoenergetic spectrum of the accelerated subfemtosecond high-charge electron bunches is shown to be nearly CEP independent.
, , Hideo Nagatomo, Toshihiro Somekawa, King Fai Farley Law, , Yasunobu Arikawa,
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.165001

Abstract:
Ablative Rayleigh-Taylor instability growth was investigated to elucidate the fundamental physics of thermal conduction suppression in a magnetic field. Experiments found that unstable modulation growth is faster in an external magnetic field. This result was reproduced by a magnetohydrodynamic simulation based on a Braginskii model of electron thermal transport. An external magnetic field reduces the electron thermal conduction across the magnetic field lines because the Larmor radius of the thermal electrons in the field is much shorter than the temperature scale length. Thermal conduction suppression leads to spatially nonuniform pressure and reduced thermal ablative stabilization, which in turn increases the growth of ablative Rayleigh-Taylor instability.
U. A. Acharya, C. Aidala, Y. Akiba, M. Alfred, V. Andrieux, N. Apadula, H. Asano, B. Azmoun, V. Babintsev, N. S. Bandara, et al.
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.162001

Abstract:
Studying spin-momentum correlations in hadronic collisions offers a glimpse into a three-dimensional picture of proton structure. The transverse single-spin asymmetry for midrapidity isolated direct photons in ${p}^{↑}+p$ collisions at $\sqrt{s}=200\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{GeV}$ is measured with the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). Because direct photons in particular are produced from the hard scattering and do not interact via the strong force, this measurement is a clean probe of initial-state spin-momentum correlations inside the proton and is in particular sensitive to gluon interference effects within the proton. This is the first time direct photons have been used as a probe of spin-momentum correlations at RHIC. The uncertainties on the results are a 50-fold improvement with respect to those of the one prior measurement for the same observable, from the Fermilab E704 experiment. These results constrain gluon spin-momentum correlations in transversely polarized protons.
Fangzhou Zhao, ,
Published: 12 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166401

Abstract:
Graphene nanoribbons (GNRs) possess distinct symmetry-protected topological phases. We show, through first-principles calculations, that by applying an experimentally accessible transverse electric field, certain boron and nitrogen periodically codoped GNRs have tunable topological phases. The tunability arises from a field-induced band inversion due to an opposite response of the conduction- and valence-band states to the electric field. With a spatially varying applied field, segments of GNRs of distinct topological phases are created, resulting in a field-programmable array of topological junction states, each may be occupied with charge or spin. Our findings not only show that electric field may be used as an easy tuning knob for topological phases in quasi-one-dimensional systems, but also provide new design principles for future GNR-based quantum electronic devices through their topological characters.
Xi Zhang, Kan-Ting Tsai, Ziyan Zhu, Wei Ren, Yujie Luo, Stephen Carr, Mitchell Luskin, Efthimios Kaxiras,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166802

Abstract:
Layers of two-dimensional materials stacked with a small twist angle give rise to beating periodic patterns on a scale much larger than the original lattice, referred to as a “moiré superlattice.” Here, we demonstrate a higher-order “moiré of moiré” superlattice in twisted trilayer graphene with two consecutive small twist angles. We report correlated insulating states near the half filling of the moiré of moiré superlattice at an extremely low carrier density ($\sim {10}^{10}\text{\hspace{0.17em}}\text{\hspace{0.17em}}{\mathrm{cm}}^{-2}$), near which we also report a zero-resistance transport behavior typically expected in a 2D superconductor. The full-occupancy ($\nu =-4$ and $\nu =4$) states are semimetallic and gapless, distinct from the twisted bilayer systems.
Philipp Gersema, , Mara Meyer Zum Alten Borgloh, Leon Koch, Torsten Hartmann, Alessandro Zenesini, , Junyu Lin, Junyu He,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.163401

Abstract:
We probe photoinduced loss for chemically stable bosonic ${}^{23}\mathrm{Na}{}^{87}\mathrm{Rb}$ and ${}^{23}\mathrm{Na}{}^{39}\mathrm{K}$ molecules in chopped optical dipole traps, where the molecules spend a significant time in the dark. We expect the effective two-body decay to be significantly suppressed due to the small expected complex lifetimes of about 13 and $6\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mu \mathrm{s}$ for ${}^{23}\mathrm{Na}{}^{87}\mathrm{Rb}$ and ${}^{23}\mathrm{Na}{}^{39}\mathrm{K}$, respectively. However, instead we do not observe any suppression of the two-body loss in parameter ranges where large loss suppressions are expected. We believe these unexpected results are most probably due to drastic underestimation of the complex lifetime by at least 1–2 orders of magnitude.
Zezhu Wei, V. F. Mitrović, D. E. Feldman
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.167204

Abstract:
Aharonov-Bohm interferometry is the most direct probe of anyonic statistics in the quantum Hall effect. The technique involves oscillations of the electric current as a function of the magnetic field and is not applicable to Kitaev spin liquids and other systems without charged quasiparticles. Here, we establish a novel protocol, involving heat transport, for revealing fractional statistics even in the absence of charged excitations, as is the case in quantum spin liquids. Specifically, we demonstrate that heat transport in Kitaev spin liquids through two distinct interferometer’s geometries, Fabry-Perot and Mach-Zehnder, exhibit drastically different behaviors. Therefore, we propose the use of heat transport interferometry as a probe of anyonic statistics in charge insulators.
Kohei Yoshimura,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.160601

Abstract:
We generalize the thermodynamic uncertainty relation (TUR) and thermodynamic speed limit (TSL) for deterministic chemical reaction networks (CRNs). The scaled diffusion coefficient derived by considering the connection between macro- and mesoscopic CRNs plays an essential role in our results. The TUR shows that the product of the entropy production rate and the ratio of the scaled diffusion coefficient to the square of the rate of concentration change is bounded below by two. The TSL states a trade-off relation between speed and thermodynamic quantities, the entropy production, and the time-averaged scaled diffusion coefficient. The results are proved under the general setting of open and nonideal CRNs.
Dean Korošak, , Boris Podobnik, Andraž Stožer, Jurij Dolenšek, ,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.168101

Abstract:
$\beta$ cells are biologically essential for humans and other vertebrates. Because their functionality arises from cell-cell interactions, they are also a model system for collective organization among cells. There are currently two contradictory pictures of this organization: the hub-cell idea pointing at leaders who coordinate the others, and the electrophysiological theory describing all cells as equal. We use new data and computational modeling to reconcile these pictures. We find via a network representation of interacting $\beta$ cells that leaders emerge naturally (confirming the hub-cell idea), yet all cells can take the hub role following a perturbation (in line with electrophysiology).
Hong Liu, Allan H. MacDonald,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.166801

Abstract:
We explain the strong interlayer drag resistance observed at low temperatures in bilayer electron-hole systems in terms of an interplay between local electron-hole-pair condensation and disorder-induced carrier density variations. Smooth disorder drives the condensate into a granulated phase in which interlayer coherence is established only in well-separated and disconnected regions, or grains, within which the densities of electrons and holes accidentally match. The drag resistance is then dominated by Andreev-like scattering of charge carriers between layers at the grains that transfers momentum between layers. We show that this scenario can account for the observed dependence of the drag resistivity on temperature and, on average, charge imbalance between layers.
, Andrew Y. Guo, Christopher L. Baldwin, Adam Ehrenberg, Alexey V. Gorshkov, Andrew Lucas
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.160401

Abstract:
The Lieb-Robinson theorem states that information propagates with a finite velocity in quantum systems on a lattice with nearest-neighbor interactions. What are the speed limits on information propagation in quantum systems with power-law interactions, which decay as $1/{r}^{\alpha }$ at distance $r$? Here, we present a definitive answer to this question for all exponents $\alpha >2d$ and all spatial dimensions $d$. Schematically, information takes time at least ${r}^{\mathrm{min}\left\{1,\alpha -2d\right\}}$ to propagate a distance $r$. As recent state transfer protocols saturate this bound, our work closes a decades-long hunt for optimal Lieb-Robinson bounds on quantum information dynamics with power-law interactions.
Martin Wimmer, Monika Monika, , Ulf Peschel,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.163901

Abstract:
Hydrodynamic phenomena can be observed with light thanks to the analogy between quantum gases and nonlinear optics. In this Letter, we report an experimental study of the superfluid-like properties of light in a ($1+1$)-dimensional nonlinear optical mesh lattice, where the arrival time of optical pulses plays the role of a synthetic spatial dimension. A spatially narrow defect at rest is used to excite sound waves in the fluid of light and measure the sound speed. The critical velocity for superfluidity is probed by looking at the threshold in the deposited energy by a moving defect, above which the apparent superfluid behavior breaks down. Our observations establish optical mesh lattices as a promising platform to study fluids of light in novel regimes of interdisciplinary interest, including non-Hermitian and/or topological physics.
Juan Román-Roche, ,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.167201

Abstract:
A system of magnetic molecules coupled to microwave cavities ($LC$ resonators) undergoes the equilibrium superradiant phase transition. The transition is experimentally observable. The effect of the coupling is first illustrated by the vacuum-induced ferromagnetic order in a quantum Ising model and then by the modification of the magnetic phase diagram of ${\mathrm{Fe}}_{8}$ dipolar crystals, exemplifying the cooperation between intrinsic and photon-induced spin-spin interactions. Finally, a transmission experiment is shown to resolve the transition, measuring the quantum electrodynamical control of magnetism.
Young Woo Choi,
Published: 11 October 2021
Physical Review Letters, Volume 127; https://doi.org/10.1103/physrevlett.127.167001

Abstract:
Graphene moiré superlattices are outstanding platforms to study correlated electron physics and superconductivity with exceptional tunability. However, robust superconductivity has been measured only in magic-angle twisted bilayer graphene (MA-TBG) and magic-angle twisted trilayer graphene (MA-TTG). The absence of a superconducting phase in certain moiré flat bands raises a question on the superconducting mechanism. In this work, we investigate electronic structure and electron-phonon coupling in graphene moiré superlattices based on atomistic calculations. We show that electron-phonon coupling strength $\lambda$ is dramatically different among graphene moiré flat bands. The total strength $\lambda$ is very large ($\lambda >1$) for MA-TBG and MA-TTG, both of which display robust superconductivity in experiments. However, $\lambda$ is an order of magnitude smaller in twisted double bilayer graphene (TDBG) and twisted monolayer-bilayer graphene (TMBG) where superconductivity is reportedly rather weak or absent. We find that the Bernal-stacked layers in TDBG and TMBG induce sublattice polarization in the flat-band states, suppressing intersublattice electron-phonon matrix elements. We also obtain the nonadiabatic superconducting transition temperature ${T}_{c}$ that matches well with the experimental results. Our results clearly show a correlation between strong electron-phonon coupling and experimental observations of robust superconductivity.
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