Renormalization of the conduction band spectrum in HgTe quantum wells by electron-electron interaction

TL;DR

This study investigates how electron-electron interactions renormalize the conduction band spectrum in HgTe quantum wells, revealing a significant deviation from theoretical predictions as the well width increases beyond a critical value.

Contribution

It provides experimental evidence of spectrum renormalization in HgTe quantum wells due to electron-electron interactions, especially for widths greater than 7-8 nm.

Findings

Effective mass matches calculations for d<6.3 nm

Mass becomes less than calculated for d>7-8 nm

Maximum deviation occurs at d=15-18 nm

Abstract

The energy spectrum of the conduction band in HgTe/Cd$_x$Hg$_{1-x}$Te quantum wells of 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 $d_c\simeq6.3$ 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 electron-electron interaction.