Excitons without effective mass: biased bilayer graphene

TL;DR

This paper develops a semi-analytic theory to study excitons in two-dimensional materials like biased bilayer graphene, where non-parabolic dispersion invalidates the effective mass approximation, providing insights into excitonic properties relevant to experiments.

Contribution

The paper introduces a semi-analytic approach to analyze excitons in 2D semiconductors with non-parabolic dispersion, specifically applied to biased bilayer graphene.

Findings

Determination of excitonic ground and excited states.

Calculation of oscillator strengths and magnetic moments.

Comparison with recent experimental data.

Abstract

Understanding the dynamics of excitons in two dimensional semiconductors requires a theory that incorporates the essential physics distinct from their three-dimensional counterparts. In addition to the modified dielectric environment, single-particle states with strongly non-parabolic dispersion appear in many two-dimensional band structures, so that "effective mass" is ill-defined. Focusing on electrostatically-biased bilayer graphene as an example where quartic (and higher) dispersion terms are necessary, we present a semi-analytic theory used to investigate the properties of ground and excited excitonic states. This includes determination of relative oscillator strengths and magnetic moments (g-factors) which can be directly compared to recent experimental measurements.