Anomalous Behavior of the Dephasing Time in Open Diffusive Cavities

Abstract

The dephasing due to electron–electron Coulomb interactions is studied for open mesoscopic cavities in the diffusive regime where l⁄λ_F>>1 (l: elastic mean free path, λ_F: Fermi wavelength). We consider a square cavity with area L×L, which is connected to reservoirs through a pair of thin leads of width W. It is assumed that L>>W>>l. The system is characterized by the lowest eigenvalue Γ₀ of a diffusion equation. We find that the temperature dependence of the dephasing time τ_φ changes whether temperature T is higher or lower than T_cross≡Γ₀⁄k_B. It is shown that τ_φ behaves as τ_φ⁻¹∝T when T>>T_cross. If T is decreased below T_cross, the T-dependence of τ_φ crosses over to τ_φ⁻¹∝T². It is also shown that in the high-temperature regime of T>>T_cross, the dephasing time is greatly reduced in comparison with that in an ordinary two-dimensional system.