The spin-1/2 Heisenberg antiferromagnetic chain is ideal for realizing one of the simplest gapless quantum spin-liquids (QSLs), supporting a many-body ground state whose elementary excitations are fractional fermionic excitations called spinons. Here we report the discovery of such a 1D QSL in Cs4CuSb2Cl12. Compared to previously reported S = 1/2 1D chains, this material possesses a wider temperature range over which the QSL state is stabilized. We identify spinon excitations extending at T > 0.8 K, with a large T-linear contribution to the specific heat, gamma = 31.5(2) mJ mol-1 K-2 which contribute itinerantly to thermal transport up to temperatures as high as T = 35 K. At T = 0.7 K, we find a second-order phase transition, suggesting a weak spin-Peierls transition that is unchanged by a 5 T magnetic field. Cs4CuSb2Cl12 reveals new phenomenology deep in the 1D QSL regime, supporting a gapped QSL phase over a wide temperature range compared to many other experimental realizations.
@article{arxiv.1907.02847,
title = {Spinon Excitations in the Quasi-1D S = 1/2 Chain Cs4CuSb2Cl12},
author = {Thao T. Tran and Chris A. Pocs and Yubo Zhang and Michal J. Winiarski and Jianwei Sun and Minhyea Lee and Tyrel M. McQueen},
journal= {arXiv preprint arXiv:1907.02847},
year = {2020}
}