Finite-temperature properties of quantum antiferromagnets in a uniform magnetic field in one and two dimensions

Abstract
Consider a d-dimensional antiferromagnet with a quantum disordered ground state and a gap to bosonic excitations with nonzero spin. In a finite external magnetic field, this antiferromagnet will undergo a phase transition to a ground state with nonzero magnetization, describable as the condensation of a dilute gas of bosons. The finite-temperature properties of the Bose gas in the vicinity of this transition are argued to obey a hypothesis of zero scale-factor universality for dd=2. Scaling properties of various experimental observables are computed in an expansion in ε=2-d, and exactly in d=1.
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