Spinon excitations in the quasi-one-dimensional $S = \frac{1}{2}$ chain compound Cs4CuSb2Cl12

• Published in: Physical review. B 2020-06, Vol.101 (23)
• Main Authors: Tran, Thao T., Pocs, Chris A., Zhang, Yubo, Winiarski, Michal J., Sun, Jianwei, Lee, Minhyea, McQueen, Tyrel M.
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Materials Science; Physics
• ISSN: 2469-9950; 2469-9969

The spin-$\frac{1}{2}$ 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 one-dimensional (1D) QSL in Cs4CuSb2Cl12. Compared to previously reported $S = \frac{1}{2}$ 1D chains, this material possesses a wider temperature range over which the QSL state is stabilized. In this work, we identify spinon excitations extending at $\textit{T}$ > 0.8 K, with a large $\textit{T}$-linear contribution to the specific heat, γ = 31.5(2)mJ mol–1 K–2, which contribute itinerantly to thermal transport up to temperatures as high as $\textit{T}$ = 35 K. At $\textit{T}$ = 0.7 K , we find a second-order phase transition that is unchanged by a $μ_0H = 5T$ 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.