Electronic Properties of Graphene/h-BN Bilayer Superlattices

Abstract

We study the electronic properties of superlattices composed of a graphene and hexagonal boron nitride (h-BN) bilayer in the framework of density functional theory. Depending on the stacking sequences of superlattices, various interesting electronic properties are observed. The stable superlattice with the shortest stacking period is found to be a narrow-gap semiconductor with a very small effective mass. On the other hand, almost linear dispersion relations should appear around the K point in a stable superlattice with a longer stacking period. These almost linear bands are found to split owing to weak but finite inter-graphene interactions mediated by h-BN bilayers.

Direct observation of heavy quasiparticles in the Kondo-lattice compound CeIn3

“…4(d) accompanied with weak spectral intensities. Those results agree well with the calculations 26 , where bands α, β, γ exhibit obvious hybridizations with f bands.…”

“…2(a)-(d). Those experimental band structures agree well with the calculation results 26,28 and are mainly derived from Ce 5d and In 5p orbitals. Since the β band is mainly derived from the In 5p orbital and 121 eV photons are more surface-sensitive than 590 eV photons, more contributions from In 5p orbitals may be observed from the 121 eV spectra on the In layer-terminated surface, which makes the β band much stronger in Figs.…”

“…1(d) and those from dHvA. Previous dHvA experiments and related calculation results 19,26,27 indicate that the dHvA frequency for the pressured paramagnetic (PM) CeIn3 is about 4 f , respectively. 22,29 Additionally, two broad and flat bands located at 2 eV and 1.5 eV BE can also be observed in Fig.…”

“…Previously, dHvA experiments, calculations and ACAR results 18,19,26,27 all indicate that there are three pronounced FS sheets for CeIn3. One electron pocket is centred at the R point, the other two centred at the Γ point (one electron and one hole).…”

Spontaneous Multipole Ordering by Local Parity Mixing

“…For instance, there are several f -electron materials possessing the lattice structures without local inversion symmetry, such as ferromagnetic superconductors UGe 2 , [28][29][30] URhGe, [31][32][33] and UCoGe, [34][35][36] the zig-zag chain compounds LnM 2 Al 10 (Ln=Ce, Nd, Gd, Dy, Ho, and Er; M=Fe, Ru, and Os), [37][38][39][40][41][42][43][44] the distorted honeycomb compounds αand β-YbAlB 4 , [45][46][47] and the diamond-structure compounds RT 2 X 20 (R=Pr, La, Yb, and U, T =Fe, Co, Ti, V, Nb, Ru, Rh, and Ir, and X =Al and Zn). [48][49][50][51][52][53][54][55][56][57][58][59] Although these materials can be candidates for unusual odd-parity multipole ordering through the local parity mixing, their properties have not been studied from such a viewpoint. In order to stimulate experiments and theories, it is important to clarify the microscopic mechanism for odd-parity multipole ordering.…”