Gapless spinons and a field-induced soliton gap in the hyper-honeycomb Cu oxalate framework compound [(C$_{2}$H$_{5}$)$_{3}$NH]$_{2}$Cu$_{2}$(C$_{2}$O$_{4}$)$_{3}$

• DOI: 10.48550/arxiv.2306.13598
• Publication Date: 2023-01-01
• Authors: C. Dissanayake; A. C. Jacko; K. Kumarasinghe; Riffat Munir; H. Siddiquee; W. J. Newsome; Fernando J. Uribe...; E. S. Choi; Swapnil Yadav; Xiaozhi Hu; Y. Takano; Santanu Pakhira; D. C. Johnston; Q. -P. Ding; Y. Furukawa; B. J. Powell; Yasuyuki Nakajima
• Keywords: Condensed Matter - Strongly Correlated Electrons; Strongly Correlated Electrons (cond-mat.str-el); FOS: Physical sciences

We report a detailed study of the specific heat and magnetic susceptibility single crystals spin liquid candidate: hyper-honeycomb Cu oxalate framework compound [(C$_2$H$_5$)$_3$NH]$_2$Cu$_2$(C$_2$O$_4$)$_3$. The shows no anomaly associated with transition at low temperatures down to $T\sim$ 180 mK in zero field. observe large linear-in-$T$ contribution $\gamma T$, = 98(1)$ mK/mol K$^{2}$, temperatures, indicative presence fermionic excitations despite Mott insulating state. low-$T$ is strongly suppressed by applied fields $H$, which induce an energy gap, $\Delta (H)$, spin-excitation spectrum. use four-component relativistic density-functional theory (DFT) calculate interactions, including Dzyaloshinskii-Moriya antisymmetric exchange, causes effective staggered field acting on one copper sublattice. magnitude dependence field-induced (H) \propto H^{2/3}$, are accurately predicted soliton mass calculated from sine-Gordon model weakly coupled antiferromagnetic Heisenberg chains all parameters determined our DFT calculations. Thus experiment calculations entirely consistent [(C$_2$H$_5$)$_3$NH]$_2$Cu$_2$(C$_2$O$_4$)$_3$ anisotropic exchange interactions due Jahn-Teller distortion cause sublattice dimerize, leaving second chains. also show that this quantitatively accounts for measured temperature-dependent susceptibility. canonical example one-dimensional spin-1/2 antiferromagnet not resonating-valence-bond quantum liquid, as previously proposed.