Magnetic field–temperature phase diagram of the quasi-two-dimensional organic superconductorλ−(BETS)2GaCl4

Abstract

The thermal conductivity κ of the quasi-two-dimensional (Q2D) organic superconductor λ-(BETS)2GaCl4 was studied in the magnetic field H applied parallel to the Q2D plane. The phase diagram determined from this bulk measurement shows notable dependence on the sample quality. In dirty samples the upper critical field Hc2 is consistent with the Pauli paramagnetic limiting, and a sharp change is observed in κ(H) at H c2 . In contrast in clean samples Hc2(T ) shows no saturation towards low temperatures and the feature in κ(H) is replaced by two slope changes reminiscent of second-order transitions. The peculiarity was observed below ∼0.33Tc and disappeared on field inclination to the plane when the orbital suppression of superconductivity became dominant. This behavior is consistent with the formation of a superconducting state with spatially modulated order parameter in clean samples.

Emerging evidence for FFLO states in layered organic superconductors (Review Article)

“…These well-studied materials [8][9][10][11][12] are strong type-II spin-singlet superconductors of high purity with long mean free pathes. During the last years, there indeed have been a number of reports giving growing evidence for the existence of an FFLO state in 2D organic superconductors [13][14][15][16][17][18][19][20].…”

Angular-dependent upper critical field of overdoped Ba(Fe1−xNix)2Murphy1, Tanatar2, Graf3 et al. 2013Phys. Rev. BSelf Cite235150View full textAdd to dashboardCite

“…[8][9][10][11][12] They stimulated a series of experimental studies, in particular in Sr 2 RuO 4 , 13-15 heavy fermion 16 and organic superconductors. [17][18][19][20][21] Although these developments were correctly catching the importance of the anisotropy of the superconducting gap structure for the angular-dependent H c2 , the theoretical data analysis was oversimplified by assumption of simple cylindrical or spherical Fermi surface shapes. The importance of the Fermi surface topology for the anisotropy of the H c2 was brought to focus by the discovery of pronounced multi-band effects in superconductivity of MgB 2 .…”

Fulde-Ferrell-Larkin-Ovchinnikov state in disordereds-wave superconductors

“…Nowadays such states are collectively known as the Fulde-FerrellLarkin-Ovchinnikov (FFLO) state. Recently the FFLO state has received renewed interest due to experimental evidence of its existence in various superconductors, 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27 and the (thus far theoretical) possibility of its realization in trapped cold atom systems, 28,29 nuclear matter and in the core of neutron stars. 30 Soon after the original work of FFLO, it was found that the FFLO state is very sensitive to the presence of impurities, and eventually suppressed when the disorder strength reaches certain critical value.…”