Interaction Induced Magnetotransport in a 2D Dirac-Heavy Hole Hybrid Band System

TL;DR

This study demonstrates that electron–electron interactions can markedly modify magnetotransport in a non-Galilean 2D system realized by a gapless HgTe quantum well hosting coexisting Dirac-like and heavy-hole bands. A Boltzmann framework with a two-subband model and intervalley scattering, augmented by temperature-dependent inelastic hole–hole processes, captures the observed large positive magnetoresistance, enhanced Hall response, and a robust $T^2$ scaling of resistivity. The extracted scattering rates show a universal $T^2$ behavior, underscoring a dominant role for interparticle interactions in hybrid-band magnetotransport. The methodology and findings offer a pathway to understand transport in other hybrid Dirac/parabolic systems, including topological insulators and Weyl semimetals, where mixed dispersions and thermally activated interband scattering govern conductivity.

Abstract

While electron-electron (e-e) interactions are known to influence resistivity in non-Galilean invariant two-dimensional (2D) systems, their effect on magnetotransport is not fully understood. Conventional models for simple bands often predict a vanishing magnetoresistivity from e-e interactions alone. In this work, we investigate magnetotransport in a gapless 6.3 nm HgTe quantum well, a hybrid 2D band system that hosts coexisting holes with both linear (Dirac-like) and parabolic energy bands. Focusing on the high temperature regime where particle-particle collisions dominate scattering, we observe significant corrections to both the magnetoresistivity and the Hall effect. The high temperature transport coefficients are in good agreement with the theoretical model describing transport in massive-massless fermion mixtures governed by a frictional mechanism and intervalley scattering. Our findings provide strong experimental validation for this theoretical framework, demonstrating that collisions between particles with different dispersions are a key mechanism governing magnetotransport in hybrid band semimetals.

Figures (5)

• Figure 1: (a) Schematic of the transistor. (b) A top view of the sample. (c) Schematic representation of the energy spectrum of a 6.3-nm mercury telluride quantum well. (d) The resistivity of HgTe quantum well as a function of the gate voltage for different samples.
• Figure 2: Gate voltage dependence of magnetoresistivity (a) and Hall effect (b) for different temperature in the hole transport regime (sample A), $P_{total}=3.2\times 10^{11} cm^{-2}$ The gate voltage was varied in 2 K steps. The dashed line represents the Hall resistance calculated using the single-carrier model. Panels (c) and (d) show the calculated B dependence of the magnetoresistivity and Hall effect at different temperature, respectively, based on Equations (4)–(10). The fitting parameters used in the calculations are presented in Fig. 3.
• Figure 3: (a) The magnetoresistivity for different temperatures with substracted $\rho(B=0)$, measured at a fixed gate voltage $V_{g} - V_{\text{CNP}} = 3.4\,\text{V}$ (sample A). (b) Zero-field resistivity excess at $B = 0\,\text{T}$ (black circles), and magnetoresistivity excess defined as $\Delta\rho(10 K) - \Delta\rho(T)$ at $B = 0.35\,\text{T}$ (red circles), plotted as a function of temperature. Red and blue lines the calculated magnetoresistivity from Equation (1) with parameters indicated in the text, blue line shows $T^2$ dependence.
• Figure 4: Gate voltage dependence of magnetoresistivity (a) and Hall effect (b) for different temperature in the hole transport regime (sample B), $P_{total}=3.2\times 10^{11} cm^{-2}$ The gate voltage was varied in 2 K steps. The dashed line represents the Hall resistance calculated using the single-carrier model. Panels (c) and (d) show the calculated B dependence of the magnetoresistivity and Hall effect at different temperature, respectively, based on Equations (4)–(10). The fitting parameters used in the calculations are presented in Fig. 5.
• Figure 5: (a) The parameters $K_{i}$ of the scattering matrix ( eq.1) extracted from comparison with equations 1-10 for sample A (black marks) and sample B(red marks). (b) The parameter $\Delta K_{i}=K_{i}(T)-K_{i}(T=10K)$ of the scattering matrix ( eq.1) as a function of the temperature. Solid line is relaxation rate $\frac{1}{\tau_{dh}}\sim T^{2}$ calculated from equation \ref{['time']}.