Muon Spin Rotation study of the $(TMTSF)_2ClO_4$ system

TL;DR

This study investigates the superconducting and magnetic properties of the organic compound $(TMTSF)_2 ClO_4$ using muon spin rotation, revealing different phases depending on cooling rate and providing detailed magnetic field distribution measurements.

Contribution

It provides the first muon spin rotation analysis of $(TMTSF)_2 ClO_4$, highlighting the effects of cooling rate on its superconducting and mixed phase states.

Findings

Superconductivity observed below 1.2 K in relaxed state

Mixed phase with coexisting superconducting and SDW regions in intermediate state

Vortex lattice formation below 0.87 K

Abstract

We report a study of the organic compound $(TMTSF)_2 ClO_4$ in both a sample cooled very slowly through the anion ordering temperature (relaxed state) and a sample cooled more rapidly (intermediate state). For the relaxed state the entire sample is observed to be superconducting below about T_c ~ 1.2 K. The second moment of the internal field distribution was measured for the relaxed state yielding an in-plane penetration depth of ~ 12000 Angstroms. The intermediate state sample entered a mixed phase state, characterized by coexisting macroscopic sized regions of superconducting and spin density wave (SDW) regions, below T_c ~ 0.87 K. These data were analyzed using a back-to-back cutoff exponential function, allowing the extraction of the first three moments of the magnetic field distribution. Formation of a vortex lattice is observed below 0.87 K as evidenced by the diamagnetic shift for the two fields in which we took intermediate state data.