Microscopic phase separation in triangular-lattice quantum spin magnet kappa-(BEDT-TTF)2Cu2(CN)3 probed by muon spin relaxation

TL;DR

This study uses muon spin relaxation to reveal microscopic phase separation in the ground state of a geometrically frustrated quantum spin system, providing insights into its complex magnetic behavior at ultra-low temperatures.

Contribution

It demonstrates microscopic phase separation in kappa-(BEDT-TTF)2Cu2(CN)3, clarifying its ground state properties and resolving conflicting reports on its magnetic gap status.

Findings

Microscopic phase separation observed below 0.1 K

Ground state exhibits coexistence of different magnetic phases

Results suggest complex, non-uniform spin dynamics

Abstract

The ground state of the quantum spin system kappa-(BEDT-TTF)2Cu2(CN)3 in which antiferromagnetically-interacting S=1/2 spins are located on a nearly equilateral triangular lattice attracts considerable interest both from experimental and theoretical aspects, because a simple antiferromagnetic order may be inhibited because of the geometrical frustration and hence an exotic ground state is expected. Furthermore, recent two reports on the ground state of this system have made it further intriguing by showing completely controversial results; one indicates the gapless state and the other gapped. By utilizing microscopic probe of muSR, we have investigated its spin dynamics below 0.1 K, unveiling its microscopically phase separated ground state at zero field.