Quantum Spin Liquid in Organic Insulators and $$^3\mathrm{He}$$

Abstract

In this chapter, we consider the low-temperature thermal conductivity of SCQSL. Measurements collected on insulators with geometrical frustration produce important experimental facts shedding light on the nature of quantum spin liquid composed of spinons. We employ the model of strongly correlated quantum spin liquid located near the topological fermion condensation phase transition to analyze the exciting measurements of the low-temperature thermal conductivity in magnetic fields collected on the organic insulators \(\mathrm{EtMe_3Sb[Pd(dmit)_2]_2}\) and \(\mathrm{\kappa -(BEDT-TTF)_2Cu_2(CN)_3}\) . Our analysis of the conductivity allows us to reveal a strong dependence of the effective mass of spinons on magnetic fields, to detect a scaling behavior of the conductivity, and to relate it to both the spin-lattice relaxation rate and the magnetoresistivity. Our calculations and observations are in a good agreement with experimental data. On the example of two-dimensional (2D) \(^3\mathrm{He}\) , we demonstrate that the main universal features of its thermodynamic properties look like those of the heavy-fermion metals and SCQSL. Our theoretical analysis of 2D \(^3\mathrm{He}\) allows us to show that the fermion condensation theory describes experimental facts in 2D \(^3\mathrm{He}\) in unified manner, and to demonstrate that the universal behavior of effective mass \(M^*\) coincides with that observed in HF metals and SQCSL, and to conclude that 2D \(^3\mathrm{He}\) represents SCQSL. This observation opens a novel way to explore the properties of quantum frustrated magnets holding a spin liquid.