Quantum Melting of the Quasi-Two-Dimensional Vortex Lattice inκ-(ET)2Cu(NCS

Abstract

We report torque magnetization measurements in regions of the mixed state phase diagram ( B approximately mu(o)H(c2) and T(c)/10(3)) of the organic superconductor kappa-(ET)2Cu(NCS)(2), where quantum fluctuations are expected to dominate thermal effects. Over most of the field range below the irreversibility line ( B(irr)), magnetothermal instabilities are observed in the form of flux jumps. The abrupt cessation of these instabilities just below B(irr) indicates a quantum melting transition from a quasi-two-dimensional vortex lattice phase to a quantum liquid phase.

Superconducting fluctuations and the reduced dimensionality of the organic superconductorκ−(BEDT−TTF)2Cu(Clayton1, Ito2, Hayden3 et al. 2002Phys. Rev. B151120View full textAdd to dashboardCite

“…7. The B irr was found to have a 1/cos θ angular dependence, in agreement with the angle-dependent torque measurements 12,14 . This may be taken as evidence for strong 2D nature of the superconductivity in κ-(BEDT-TTF) 2 Cu(NCS) 2 .…”

“…2). The relationship of the irreversibility field and the field at which the flux lattice melts remains controversial in this compound 13,14 . The DHVA signal is observed only above B irr , in the vortex liquid phase, where the magnetization is fully reversible.…”

“…The low dimensionality together with short coherence length, result in fluctuations of the superconducting order parameter being important over a wide range in temperature and applied field. The importance of thermal 4,7,8,15,16 or quantum fluctuations 13,14,17 leads to, for example, a broadened anomaly in the specific heat capacity. The superconducting phase diagram of κ-(BEDT-TTF) 2 Cu(NCS) 2 has a complicated structure 14,18,19 .…”

New insights on frequency combinations and ‘forbidden frequencies’ in the de Haas–van Alphen spectrum ofκ-(ET)2Cu(SCN)2

“…Fig. 1(a) displays magnetic torque data at 1.7 K. As expected, a strong hysteresis is observed in the superconducting state at low field due to flow of magnetic flux either into or out of the crystal as the field either increases or decreases [34]. In contrast, data for up and down fields are indiscernible from each other in the range where oscillations are observed.…”

New Method for Torque Magnetometry Using a Commercially Available Membrane-Type Surface Stress Sensor

“…A spike-like feature was observed only in sweep-down measurement. This is considered to be related to a flux jump 15,16 . It should be mentioned that the upper critical field for the fields perpendicular and parallel to the superconducting layers are estimated to be µ 0 H ⊥ c2 > 5 T and µ 0 H c2 > 50 T 13,14 .…”