Evidence of Unconventional Universality Class in a Two-Dimensional Dimerized Quantum Heisenberg Model

Wenzel, Sandro; Bogacz, Leszek; Janke, Wolfhard

Evidence of Unconventional Universality Class in a Two-Dimensional Dimerized Quantum Heisenberg Model

Authors

Wenzel, Sandro

Bogacz, Leszek

Janke, Wolfhard

Description

The two-dimensional $J$-$J^\prime$ dimerized quantum Heisenberg model is studied on the square lattice by means of (stochastic series expansion) quantum Monte Carlo simulations as a function of the coupling ratio \hbox{$α=J^\prime/J$}. The critical point of the order-disorder quantum phase transition in the $J$-$J^\prime$ model is determined as \hbox{$α_\mathrm{c}=2.5196(2)$} by finite-size scaling for up to approximately $10 000$ quantum spins. By comparing six dimerized models we show, contrary to the current belief, that the critical exponents of the $J$-$J^\prime$ model are not in agreement with the three-dimensional classical Heisenberg universality class. This lends support to the notion of nontrivial critical excitations at the quantum critical point.
4+ pages, 5 figures, version as published