Superconducting fluctuations and the reduced dimensionality of the organic superconductorκ−(BEDT−TTF)2Cu(

Abstract

We report measurements of the de Haas-van Alphen (DHVA) effect and AC susceptibility in the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2. The amplitude of the DHVA oscillations is attenuated over a wide field range above the irreversibility line, Birr(B), below which a rigid flux lattice is formed. Thus the DHVA effect provides a unique probe of the superconducting fluctuations at high fields in this material. We compare our measurements with other determinations of the superconducting phase diagram of κ-(BEDT-TTF)2Cu(NCS)2.

Damping of the de Haas–van Alphen oscillations in the superconducting state ofMgB2

“…This form of ∆(B) was used by Clayton et al 23 to account for the effect of superconducting fluctuations, as it interpolating the mean field result at low field to the form expected for a strongly fluctuating system near H c2 . The phenomenological parameter α sets the strength of the fluctuations.…”

Quantum oscillations in the vortex liquid state of the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2

“…The parameters of the LK formula are obtained by fitting the data in the normal state above 7 T: Below about 7 T the amplitude starts to deviate smoothly downward from A 2D LK in both data of the dHvA and SdH effects. This indicates the additional amplitude damping in the vortex state, which has been reported so far on the dHvA effect in k-ðBEDT-TTFÞ 2 CuðNCSÞ 2 [5,[9][10][11]. The origin of such smooth damping has been discussed on the basis of the model of the quasiparticle scattering by the random vortex lattice with large superconducting (vortex) fluctuation around the mean field H c2 [3,11].…”

“…The tilde above D indicates that energy is measured in units of _o c : This expression is very similar to the Maki-Stephen type mean field approach [11][12][13]. In a simple analytic expression derived by Maniv et al [3], /j *…”

“…: Ito et al [9] and Clayton et al [11] have used an approximated interpolation formula for the mean square of the gap function,…”

“…This indicates the additional amplitude damping in the vortex state, which has been reported so far on the dHvA effect in k-ðBEDT-TTFÞ 2 CuðNCSÞ 2 [5,[9][10][11]. The origin of such smooth damping has been discussed on the basis of the model of the quasiparticle scattering by the random vortex lattice with large superconducting (vortex) fluctuation around the mean field H c2 [3,11]. In the approach by Maniv et al [3], the additional damping term is…”