Weak antilocalization in HgTe quantum wells with inverted energy spectra

The results of an experimental study of the magnetoconductivity of two-dimensional (2D) electron gas caused by suppression of the interference quantum correction in a HgTe single quantum well heterostructure with an inverted energy spectrum are presented. It is shown that only the antilocalization magnetoconductivity is observed at relatively high conductivity, σ(20 - 30)G 0, where G 0=e2/2π2. The antilocalization correction demonstrates a crossover from 0. 5ln(τ φ/τ) to 1.0ln(τ φ/τ) behavior with increasing conductivity (here τ φ and τ are the phase relaxation and transport relaxation times, respectively). It is interpreted as a result of crossover to the regime when the two chiral branches of the electron energy spectrum independently contribute to the weak antilocalization. At lower conductivity, σ<(20 - 30)G 0, the magnetoconductivity behaves similarly to that in usual 2D systems with fast spin relaxation: It is negative in low magnetic fields and positive in higher ones. We have found that the temperature dependences of the fitting parameter τ φ corresponding to the phase relaxation time demonstrate reasonable behavior, close to 1/T, over the whole conductivity range from 5G 0 up to 130G 0. However, the τ φ value remains practically independent of conductivity, in contrast to conventional 2D systems with simple energy spectra, in which τ φ is enhanced with conductivity. © 2012 American Physical Society