In-Plane Anisotropy of Flux-Flow Resistivity in Layered Organic Superconductor λ-(BETS)₂GaCl₄

Abstract

We recently observed in-plane fourfold-symmetric anisotropy in the flux-flow resistivity (FFR) of d-wave organic superconductor κ-(ET)2Cu(NCS)2. Origin of the fourfold-symmetric anisotropy was discussed in terms of the interplay between the Josephson-vortex dynamics and the superconducting gap structure. Here, we report the in-plane anisotropy of the FFR of layered organic superconductor λ-(BETS)2GaCl4. The in-plane angular dependence is mainly described by twofold symmetry. The dip structure appears when the magnetic field is applied parallel to the c-axis. These results are different from the case of κ-(ET)2Cu(NCS)2, even though the Fermi-surface topology of λ-(BETS)2GaCl4 is much similar to that of κ-(ET)2Cu(NCS)2. The different anisotropic behavior is discussed in terms of interlayer coupling strength.