Valley and Zeeman Splittings in Multilayer Epitaxial Graphene Revealed by Circular Polarization Resolved Magneto-infrared Spectroscopy

Abstract

Circular polarization resolved magneto-infrared studies of multilayer epitaxial graphene (MEG) are performed using tunable quantum cascade lasers in high magnetic fields up to 17.5 T. Landau level (LL) transitions in the monolayer and bilayer graphene inclusions of MEG are resolved, and considerable electron-hole asymmetry is observed in the extracted electronic band structure. For monolayer graphene, a fourfold splitting of the n = 0 to n = 1 LL transition is evidenced and attributed to the lifting of the valley and spin degeneracy of the zeroth LL and the broken electron-hole symmetry. The magnetic field dependence of the splitting further reveals its possible mechanisms. The best fit to experimental data yields effective g-factors, g * V S = 6.7 and g * ZS = 4.8, for the valley and Zeeman splitting, respectively.

Broken Symmetries and Kohn’s Theorem in Graphene Cyclotron Resonance

“…This value lies within a factor of 2 of the asymmetry energies seen here, suggesting we are seeing an intrinsic property of the underlying band structure. In contrast, far larger particle-hole asymmetries up to a few percent of E 0;1 have been reported in swept-field CR studies of graphene-on-oxide, monolayer and multilayer epitaxial graphene, and encapsulated graphene with double moiré potentials [8,9,42,43].…”

“…These phenomena have been explored by a variety of experimental probes, including electronic transport, quantum capacitance, and scanning probe microscopy experiments [1][2][3][4][5][6][7]. However, the excited states of this system due to collective excitations between Landau levels (LLs) in the broken-symmetry regime have not been explored much to date [8,9]. Graphene is an ideal platform in which to pursue such studies because, in contrast to traditional two-dimensional electron systems having a parabolic dispersion, the linear dispersion of graphene allows the contribution of many-particle interactions to directly modify the LL transition energies in measurements of the cyclotron resonance (CR).…”

“…The linear dispersion of graphene mixes these coordinates so that interactions can directly impact LL transitions [18][19][20][21][22][23], leading to deviations from Eq. (1) [8,[24][25][26][27] and a dependence of CR on the LL filling factor, ν ¼ 2πn s l 2 B , where n s is the charge carrier sheet density [28].…”

Giant $g$-factors and fully spin-polarized states in metamorphic short-period InAsSb/InSb superlattices

“…The magnetic field is applied along the growth direction (z direction) of the SLs, and the transmitted light is collected by a Si bolometer mounted beneath the sample. By adding a linear polarizer and a broadband quarter-wave plate in the light path, we can perform circular polarization resolved measurements, which further help to distinguish the optical transitions between different selection rules [37,38].…”

Electron-Hole Asymmetry of Surface States in Topological Insulator Sb2Te3 Thin Films Revealed by Magneto-Infrared Spectroscopy

“…Magneto-infrared (IR) spectroscopy is a powerful tool for precise electronic structure characterization [14,15]. Due to high carrier densities in previous TI systems [16,17], magneto-IR studies did not succeed in observing clear signatures of Landau level (LL) transition between the Dirac SSs [18][19][20][21].…”