Universal critical temperature for Kosterlitz-Thouless transitions in bilayer quantum magnets

Recent experiments show that double layer quantum Wall systems may have a g round state with canted antiferromagnetic order. In the vicinity of a quant um critical point, the order vanishes at a temperature T-KT = kappa H, wher e H is the magnetic field and kappa is a universal number. We present quant um Monte Carlo simulations on a model spin system which support the univers ality of kappa and determine its value. This allows experimental tests of a n intrinsically quantum-mechanical universal quantity, which is not also a property of a higher dimensional classical critical point. [S0031-9007(98)0 7889-2].