Electric field-induced valley degeneracy lifting in uniaxial strained graphene: Evidence from magnetophonon resonance

Abstract

A double peak structure in the magneto-phonon resonance (MPR) spectrum of uniaxial strained graphene, under crossed electric and magnetic fields, is predicted. We focus on the Γ point optical phonon modes coupled to the inter-Landau level transitions 0 ⇆ ±1 where MPR is expected to be more pronounced at high magnetic field. We derive the frequency shifts and the broadenings of the longitudinal (LO) and transverse (TO) optical phonon modes taking into account the effect of the strain modified electronic spectrum on the electron-phonon coupling. We show that the MPR line for a given phonon mode acquires a double peak structure originating from the two-fold valley degeneracy lifting. The latter is due to the different Landau level spacings in the two Dirac valleys resulting from the simultaneous action of the inplane electric field and the strain induced Dirac cone tilt. We discuss the role of some key parameters such as disorder, strain, doping and electric field amplitude on the emergence of the double peak structure.

Raman scattering of graphene‐based systems in high magnetic fields

“…, showing how polarization resolved experiments that can distinguish between the two types of doping. The complete optical phonon polarization operator, including both interband and intraband electronic excitations and polarization of the incoming and outgoing photons, was developed in Leszczynski et al Uniaxial strain, very likely to affect realistic samples at low temperatures, has also been invoked to explain details of the evolution of the MPR …”

Tunable anomalous Andreev reflection and triplet pairings in spin-orbit-coupled graphene

“…Furthermore, graphene has the capability of sustaining strain and deformations without rupture 36,37 . The application of strain to graphene layers can result in important and interesting phenomena [38][39][40][41][42][43][44][45][46][47] . For example, the interplay of massive electrons with spin orbit coupling in the presence of strain in a graphene layer yields controllable spatially separated spin-valley filtering 38,39 .…”

Magneto-optics of quasirelativistic electrons in graphene with an inplane electric field and in tilted Dirac cones inα−(BEDT TTF)2I3

“…Figure 6 shows the relation between the tilt parameter β and the location of the two peaks in the one-sided Fourier transform of the rescaled spectrum in Eq. (25). Here, we restrict our attention to 2D Weyl materials.…”