Hidden symmetries in Bechgaard salt (TMTSF)2NO3

TL;DR

This paper investigates the unique properties of (TMTSF)2NO3, revealing that its lack of superconductivity and unconventional SDW state are due to inverse symmetry breaking and novel phase behavior, expanding understanding of Bechgaard salts.

Contribution

It introduces the concept of inverse symmetry breaking caused by anion ordering and proposes a new phase diagram with unconventional SDW in Bechgaard salts.

Findings

(TMTSF)2NO3 remains semimetallic and gapless at low temperatures.

Unconventional SDW state is indicated by AMRO measurements.

A new phase diagram with USDW is proposed.

Abstract

Among known Bechgaard and Fabre salts (TMTSF)2NO3 is unique since it never becomes superconducting even under pressure. Also, though (TMTSF)2NO3 undergoes the spin density wave (SDW) transition, the low temperature transport is semimetallic and gapless. We propose: a) the absence of the superconductivity is due to the inverse symmetry breaking associated with the anion ordering at 45K; b) the SDW state below 9K should be unconventional as seen from the angle dependent magnetoresistance oscillation (AMRO); c) a new phase diagram for Bechgaard salts, where unconventional spin density wave (USDW) occupies the prominent space.