Theory of inter-Landau-level magnetoexcitons in bilayer graphene

Abstract

If bilayer graphene is placed in a strong perpendicular magnetic field, several quantum Hall plateaus are observed at low enough temperatures. Of these, the σxy = 4ne 2 /h sequence (n = 0) is explained by standard Landau quantization, while the other integer plateaus arise due to interactions. The low-energy excitations in both cases are magnetoexcitons, whose dispersion relation depends on single-and many-body effects in a complicated manner. Analyzing the magnetoexciton modes in bilayer graphene, we find that the mixing of different Landau level transitions not only renormalizes them, but essentially changes their spectra and orbital character at finite wave length. These predictions can be probed in inelastic light scattering experiments.

Symmetry characterization of the collective modes of the phase diagram of the ν=0 quantum Hall state in graphene: Mean-field phase diagram and spontaneously broken symmetries

“…At k = 0, apart from these valley-spin symmetries, the z component of the orbital pseudospin, O z , is also conserved by the Hamiltonian as it represents the angular momentum of the magnetoexciton [8,33,34]. In fact, the total orbital pseudospin O is another good quantum number in this limit.…”

“…For instance, the spectrum of inter-LL collective excitations was obtained in Refs. [8,14,34]. On the other hand, the spectrum of intra-LL excitations within the zero-energy Landau level was computed for the ν = 0 QH state [33] and the rest of integer QH states [25] allowing only for long range and interlayer Coulomb interactions.…”

“…In the first place, we briefly present the effective model used in this work for bilayer graphene, following Refs. [6,[21][22][23]34], where the reader is referred for more details.…”

Particle-hole symmetry and bifurcating ground-state manifold in the quantum Hall ferromagnetic states of multilayer graphene

“…16,17 The latter requires β (2) 17/(ǫ r B [T]) ≈ 9.2, β (3) 188/(ǫ r B [T]) ≈ 38, and β (4) 2073/(ǫ r B 3/2 [T]) ≈ 41, where we have estimated ǫ r ≈ 4 in the final numbers; 16 and for n 120/B[T] the LLs are far from ±γ 1 for any s. 16 The two-band model slightly overestimates the LL energies; 18 these ensuing quantitative modifications will be discussed below.…”

“…17 we calculated the overlap of the Landau orbitals in the presence of trigonal warping (and other hoppings) with those without trigonal warping in the four-band model of bilayer graphene. In Fig.…”