Visualizing pair formation on the atomic scale in the high-Tc superconductor Bi2Sr2CaCu2O8+δ
- 1 May 2007
- journal article
- letter
- Published by Springer Science and Business Media LLC in Nature
- Vol. 447 (7144), 569-572
- https://doi.org/10.1038/nature05881
Abstract
Pairing of electrons in conventional superconductors occurs at the superconducting transition temperature Tc, creating an energy gap Δ in the electronic density of states (DOS)1. In the high-Tc superconductors, a partial gap in the DOS exists for a range of temperatures above Tc (ref. 2). A key question is whether the gap in the DOS above Tc is associated with pairing, and what determines the temperature at which incoherent pairs form. Here we report the first spatially resolved measurements of gap formation in a high-Tc superconductor, measured on Bi2Sr2CaCu2O8+δ samples with different Tc values (hole concentration of 0.12 to 0.22) using scanning tunnelling microscopy. Over a wide range of doping from 0.16 to 0.22 we find that pairing gaps nucleate in nanoscale regions above Tc. These regions proliferate as the temperature is lowered, resulting in a spatial distribution of gap sizes in the superconducting state3,4,5. Despite the inhomogeneity, we find that every pairing gap develops locally at a temperature Tp, following the relation 2Δ/kBTp = 7.9 ± 0.5. At very low doping (≤0.14), systematic changes in the DOS indicate the presence of another phenomenon6,7,8,9, which is unrelated and perhaps competes with electron pairing. Our observation of nanometre-sized pairing regions provides the missing microscopic basis for understanding recent reports10,11,12,13 of fluctuating superconducting response above Tc in hole-doped high-Tc copper oxide superconductors.This publication has 27 references indexed in Scilit:
- Thermodynamic transitions in inhomogeneous-wave superconductorsPhysical Review B, 2006
- Doping a Mott insulator: Physics of high-temperature superconductivityReviews of Modern Physics, 2006
- The pseudogap: friend or foe of highTc?Advances in Physics, 2005
- Atomic-Scale Sources and Mechanism of Nanoscale Electronic Disorder in Bi 2 Sr 2 CaCu 2 O 8+δScience, 2005
- How to detect fluctuating stripes in the high-temperature superconductorsReviews of Modern Physics, 2003
- Microscopic electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+xNature, 2001
- Inherent inhomogeneities in tunneling spectra of crystals in the superconducting statePhysical Review B, 2001
- The doping dependence of T* – what is the real high-Tc phase diagram?Physica C: Superconductivity and its Applications, 2001
- The pseudogap in high-temperature superconductors: an experimental surveyReports on Progress in Physics, 1999
- Destruction of the Fermi surface in underdoped high-Tc superconductorsNature, 1998