Short-range interactions and scaling near integer quantum Hall transitions

We study the influence of short-range electron-electron interactions on sca ling behavior near the integer quantum Hall plateau transitions. Shea-range interactions are known to be irrelevant at the renormalization group fixed point which represents the transition in the noninteracting system. We fin d, nevertheless, that transport properties change discontinuously when inte ractions are introduced. Most importantly, in the thermodynamic limit the c onductivity at finite temperature is zero without interactions, but nonzero in the presence of arbitrarily weak interactions. In addition, scaling as a function of frequency omega and temperature T is determined by the scalin g variable omega/T-p (where p is the exponent for the temperature dependenc e of the inelastic scattering rate) and not by omega/T, as it would be at a conventional quantum phase transition described by an interacting fixed po int. We express the inelastic exponent p and the thermal exponent z(T) in t erms of the scaling dimension -alpha<0 of the interaction strength and the dynamical exponent,z (which has the value z = 2), obtaining p = 1 + 2 /z an d z(T)=2/p.