Electron mass in a HgTe quantum well: Experiment versus theory

Abstract

Abstract The energy spectrum of the conduction band in HgTe/Cd x Hg 1 − x Te quantum wells with a width d = ( 4 . 6 − 20 . 2 ) nm has been experimentally studied in a wide range of electron density. For this purpose, the electron density dependence of the effective mass was measured by two methods: by analyzing the temperature dependence of the Shubnikov–de Haas oscillations and by means of the quantum capacitance measurements. There was shown that the effective mass obtained for the structures with d d c , where d c ≃ 6 . 3 nm is a critical width of quantum well corresponding to the Dirac-like energy spectrum, is close to the calculated values over the whole electron density range; with increasing width, at d > ( 7 − 8 ) nm , the experimental effective mass becomes noticeably less than the calculated ones. This difference increases with the electron density decrease, i.e., with lowering the Fermi energy; the maximal difference between the theory and experiment is achieved at d = ( 15 − 18 ) nm , where the ratio between the calculated and experimental masses reaches the value of two and begins to decrease with a further d increase. We assume that observed behavior of the electron effective mass results from the spectrum renormalization due to many-body effects.