Ultralow-temperature behavior of the ν=5/2 fractional quantum hall effect

Abstract

The newly discovered even-denominator fractional quantum Hall effect at filling factor ν=5/2 has been studied at ultralow temperatures. While ρxx is not found to vanish in the temperature range studied, the minimum in ρxx is seen to drop at the lowest temperatures. While this drop is insufficient to determine the energy gap, Δ, it may be combined with the temperature dependence of the background resistivity to give a value of Δ∼26 mK. Because of the high electron-phonon relaxation rate, τε^-1=(2.9×10^3)T^3 sec^-1K^-3, a minimum electron temperature of 9 mK could be obtained with a residual heat leak of 8×10^-14 W. It appears likely that ρxx approaches zero as T→0.