Fermi Surface Structure and Isotropic Stability of Fulde-Ferrell-Larkin-Ovchinnikov Phase in Layered Organic Superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3

Abstract

The Fermi surface structure of a layered organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3 was determined by angular-dependent magnetoresistance oscillations measurements and band-structure calculations. This salt was found to have two small pockets with the same area: a deformed square hole pocket and an elliptic electron pocket. Characteristic corrugations in the field dependence of the interlayer resistance in the superconducting phase were observed at any in-plane field directions. The features were ascribed to the commensurability (CM) effect between the Josephson vortex lattice and the periodic nodal structure of the superconducting gap in the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase. The CM effect was observed in a similar field region for various in-plane field directions, in spite of the anisotropic nature of the Fermi surface. The results clearly showed that the FFLO phase stability is insensitive to the in-plane field directions.

New Spin on Metal-Insulator Transitions

“…In the latter case, the Fabre salts with quarter-filled bands exhibit textbook-like charge-ordered states driven by inter-site Coulomb interactions, which also give rise to unconventional superconductivity in β -(BEDT-TTF) 2 X, as reviewed by Ihara and Imajo [5]. Such layered organic superconductors are well suited to study the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state [6,7]. On the theoretical side, Riedl and coworkers review generalized models of κ-systems [8], while Tan et al assessed universal aspects of Mott criticality [9].…”