Anomalous In-Plane Anisotropy of the Onset of Superconductivity in (TMTSF)2ClO4

TL;DR

This study investigates the anisotropic behavior of the superconducting transition temperature in (TMTSF)2ClO4 under magnetic fields aligned with the conductive plane, revealing unusual in-plane anisotropy and potential FFLO phase indications.

Contribution

It provides the first detailed analysis of the in-plane anisotropy of Tc onset in (TMTSF)2ClO4 with magnetic fields aligned to the conductive plane, highlighting anomalous behavior near the Pauli limit.

Findings

Rapid increase of Tc_onset fields at low temperatures for H // a and H // b'

Shift of principal in-plane field-angle dependence near the Pauli limit

Possible evidence of Fulde-Ferrell-Larkin-Ovchinnikov phases

Abstract

We report the magnetic field-amplitude and field-angle dependence of the superconducting onset temperature Tc_onset of the organic superconductor (TMTSF)2ClO4 in magnetic fields H accurately aligned to the conductive ab' plane. We revealed that the rapid increase of the onset fields at low temperatures occurs both for H // b' and H // a, irrespective of the carrier confinement. Moreover, in the vicinity of the Pauli limiting field, we report a shift of a principal axis of the in-plane field-angle dependence of Tc_onset away from the b' axis. This feature may be related to an occurrence of Fulde-Ferrell-Larkin-Ovchinnikov phases.