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.
@article{arxiv.1204.1785,
title = {Microscopic phase separation in triangular-lattice quantum spin magnet kappa-(BEDT-TTF)2Cu2(CN)3 probed by muon spin relaxation},
author = {Saori Nakajima and Takao Suzuki and Yasuyuki Ishii and Kazuki Ohishi and Isao Watanabe and Takayuki Goto and Akira Oosawa and Naoki Yoneyama and Norio Kobayashi and Francis L. Pratt and Takahiko Sasaki},
journal= {arXiv preprint arXiv:1204.1785},
year = {2015}
}