Thermal Ising Transition in the Spin-1/2 J_1-J_2 Heisenberg Model

摘要

Using an SU(2) invariant finite-temperature tensor network algorithm, we provide strong numerical evidence in favor of an Ising transition in the collinear phase of the spin- 1/2 J_1-J_2 Heisenberg model on the square lattice. In units of J_2, the critical temperature reaches a maximal value of T_c/J_2 (≌)0.18 around J_2/J_1(≌) 1.0. It is strongly suppressed upon approaching the zero-temperature boundary of the collinear phaseJ_2/J_1(≌) 0.6, and it vanishes as 1/log(J_2/J_1) in the large J_2/J_1 limit, as predicted by Chandra et al., Phys. Rev. Lett. 64, 88 (1990). Enforcing the SU(2) symmetry is crucial to avoid the artifact of finite-temperature SU(2) symmetry breaking of U(l) algorithms, opening new perspectives in the investigation of the thermal properties of quantum Heisenberg antiferromagnets.