Magnetothermal instability in the organic layered superconductorκ−(BEDT-TTF)2Cu(NCS)2

Abstract

We have studied the magnetothermal instability in $\ensuremath{\kappa}\text{\ensuremath{-}}{(\text{BEDT-TTF})}_{2}\text{Cu}{(\text{NCS})}_{2}$ by means of measuring the temperature change in the sample. We report the remarkable temperature spikes due to the flux jumps and the preceding temperature oscillations in the vortex solid state. These dependences on the sweep rate are almost consistent with the conventional theory based on the Bean model. The temperature dependences of the flux jump suggest that the melting transition from the vortex solid to the liquid phase at low temperatures is not driven by thermal fluctuations, but rather by quantum ones. The small temperature fluctuations observed at very low temperatures imply the dendritic vortex distribution in this salt.