Majorana spin liquid and dimensional reduction in Cs2CuCl4

TL;DR

This paper models the spin-liquid behavior of Cs2CuCl4 using Majorana fermions, explaining experimental observations and revealing dimensional reduction where Majorana fermions propagate only along the strongest bonds.

Contribution

It introduces a mean-field Majorana fermion approach to explain the magnetic properties and dimensional reduction in Cs2CuCl4.

Findings

The crossover temperature T_c depends on magnetic field as observed experimentally.

Specific heat and spin susceptibility peak at T_c = J/2 in the spin-liquid regime.

Majorana fermions propagate only along the strongest bonds, supporting dimensional reduction.

Abstract

The low-temperature behavior of the magnetic insulator Cs2CuCl4 can be modeled by an anisotropic triangular lattice spin-1/2 Heisenberg antiferromagnet with two different exchange couplings J and J' = J/3. We show that in a wide range of magnetic fields the experimentally observed field dependence of the crossover temperature T_c for spin-liquid behavior can be explained within a mean-field theory based on the representation of spin operators in terms of Majorana fermions. We also show that for small magnetic fields the specific heat and the spin susceptibility both exhibit a maximum as a function of temperature at T_c = J/2. In the spin-liquid regime, the Majorana fermions can only propagate along the direction of the strongest bond, in agreement with the dimensional reduction scenario advanced by Balents [Nature (London) 464, 199 (2010)].