Inverse symmetry breaking in low-dimensional systems

Daniele Toniolo

董锟 Dong Kun

M. Yamashita

The Landau theory on the phase transition derived statistical-mechanically on the basis of the symmetry breaking potential method with the use of inverse temperature series expansion is examined. In that method an estimate of the mean field is improved systematically by taking account of short range correlations. The results at low temperatures in relation to the expansion parameter are investigated. The critical temperature obtained is equal to that in the [n, 0] Padé approximation applied to the inverse of susceptibility. By making use of many results obtained up to now in the calculation of susceptibility with the use of inverse temperature series expansion, the critical temperatures of the Ising, Heisenberg and XY models are determined. The possibility of long range ordering in low dimensional systems and the case of the symmetry breaking potential incommutative with the Hamiltonian are also investigated.

Franco Strocchi

Imre Hagymási, Robin Schäfer, Roderich Moessner +1 more

We address the ground-state properties of the long-standing and much-studied three-dimensional quantum spin liquid candidate, the S=1/2 pyrochlore Heisenberg antiferromagnet. By using SU(2) density-matrix renormalization group (DMRG), we are able to access cluster sizes of up to 128 spins. Our most striking finding is a robust spontaneous inversion symmetry breaking, reflected in an energy density difference between the two sublattices of tetrahedra, familiar as a starting point of earlier perturbative treatments. We also determine the ground-state energy, E_{0}/N_{sites}=-0.490(6)J, by combining extrapolations of DMRG with those of a numerical linked cluster expansion. These findings suggest a scenario in which a finite-temperature spin liquid regime gives way to a symmetry-broken state at low temperatures.

Klaus Dietz