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Sandro Wenzel, Leszek Bogacz, Wolfhard Janke The two-dimensional J-J' 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 α=J'/J. The critical point of the order-disorder quantum phase transition in the J-J' model is determined as αc=2.5196(2) by finite-size scaling for up to ≈ 10000 quantum spins. By comparing six dimerized models we show, contrary to the current believe, that the critical exponents of the J-J' model are not in agreement with the three-dimensional classical Heisenberg universality class which gives support to the notion of non-trivial critical excitations at the quantum critical point. |
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