Observation of charge-density waves in the cubic spinel structure CuV2S4

Abstract

We have observed charge-density-wave (CDW) phase transitions in the cubic spinel structure Cu${\mathrm{V}}_2$ ${\mathrm{S}}_4$. At 90 K a CDW forms with a reduced wave vector $\overrightarrow{\mathrm{q}}=(\frac{1}{4}-\delta )\left[110\right]\mathrm{}$. The incommensurability $\delta$ decreases with decreasing temperature, and lock-in ($\delta =0\mathrm{}$) occurs at 75 K. At about 50 K a first-order transition to a new incommensurate CDW structure with $\overrightarrow{\mathrm{q}}\approx \left(\frac{1}{3}\right)\left[110\right]\mathrm{}$ occurs. Anomalies in the magnetic susceptibility and the resistance occur at 90 and 50 K.