Pseudo-magnetoexcitons in strained graphene bilayers without external magnetic fields

TL;DR

This paper proposes a realistic strained graphene bilayer device to detect pseudo-magnetoexcitons without external magnetic fields, revealing their optical properties and phase transition behavior through analytical models.

Contribution

It introduces a new method to observe pseudo-magnetoexcitons in strained graphene bilayers without external magnetic fields, with analytical derivation of Landau levels and optical absorption spectra.

Findings

Pseudo-Landau levels are analytically derived for electron-hole pairs.

Optical absorption spectra can identify Dirac-type pseudo-magnetoexcitons.

Phase transition temperature for superfluidity is higher under inhomogeneous PMFs.

Abstract

The structural and electronic properties of graphene leads its charge carriers to behave like relativistic particles, which is described by a Dirac-like Hamiltonian. Since graphene is a monolayer of carbon atoms, the strain due to elastic deformations will give rise to so-called `pseudomagnetic fields (PMF)' in graphene sheet, and that has been realized experimentally in strained graphene sample. Here we propose a realistic strained graphene bilayer (SGB) device to detect the pseudo-magnetoexcitons (PME) in the absence of external magnetic field. The carriers in each graphene layer suffer different strong PMFs due to strain engineering, which give rise to Landau quantization. The pseudo-Landau levels (PLLs) of electron-hole pair under inhomogeneous PMFs in SGB are analytically obtained in the absence of Coulomb interactions. Based on the general analytical optical absorption selection rule for PME, we show that the optical absorption spectrums can interpret the corresponding formation of Dirac-type PME. We also predict that in the presence of inhomogeneous PMFs, the superfluidity-normal phase transition temperature of PME is greater than that under homogeneous PMFs.}