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Critical Exponents in a Quantum Phase Transition of an Anisotropic 2D Antiferromagnet

I use the two-step density-matrix renormalization group method to extract the critical exponents $β$ and $ν$ in the transition from a Néel $Q=(π,π)$ phase to a magnetically disordered phase with a spin gap. I find that the exponent $β$ computed from the magnetic side of the transition is consistent with that of the classical Heisenberg model, but not the exponent $zν$ computed from the disordered side. I also show the contrast between integer and half-integer spin cases.