Unconventional phases in a Haldane model of dice lattice

Abstract

We propose a Haldane-like model of dice lattice analogous to graphene and explore its topological properties within the tight-binding formalism. The topological phase boundary of the system is identical to that of Haldane model of graphene but the phase diagram is richer than the latter due to existence of a distorted flat band. The system supports phases which have a 'gapped-out' valence (conduction) band and an indirect overlap between the conduction (valence) band and the distorted flat band. The overlap of bands imparts metalic character to the system. These phases may be further divided into topologically trivial or non-trivial ones depending on the Chern number of the 'gapped-out' band. The semimetalic phases exist as distinct points that are well separated from each other in the phase diagram and exhibit spin-1 Dirac-Weyl dispersion at low energies. The Chern numbers of the bands in the Chern-insulating phases are 0 and ±2. This qualifies the system to be candidate for Quantum Anomalous Hall effect with two chiral channels per edge. Counterpropagating edge states emanate from the flat band in certain topologically trivial phases. The system displays beating pattern in SdH oscillations for unequal magnitude of mass terms in the two valleys. We show that the chemical potential and ratio of topological parameters of the system viz. Semenoff mass and next neighbour hopping amplitude may be experimentally determined from the number of oscillations between the beating nodes and the beat frequency respectively.

Floquet Modification of the Bandgaps and Energy Spectrum in Flat-Band Pseudospin-1 Dirac Materials

“…The presence of an unusual band structure in α-T 3 model can lead to unique and unexpected features, including electronic, [58][59][60] collective, [61][62][63] magnetic, [64] optical properties, [65][66][67][68][69] and even a phase transition [70]. These behaviors are very different from those of graphene.…”

Floquet engineering of titled and gapped Dirac materials

“…27 It was also demonstrated that the off-resonant field could substantially modify transport properties 17,41,42 , excitonic behavior 43 and topological signatures of a two-dimensional lattice. 29,[44][45][46] A molybdenum disulfide MoS 2 is one of monolayer transition-metal dichalcogenides with a distorted tetragonal structure. [47][48][49] In general, the monolayer semiconducting MoS 2 structure may assume a trigonal prismatic coordination of the metal atoms (2H with hexagonal symmetry), as well as octahedral coordination (1T with tetragonal symmetry) or 1T with a distorted and the most exotic 50,51 which is exactly the subject of our study.…”

Floquet engineering of tilted and gapped Dirac band structures in 1T'-MoS2

“…32 Meanwhile, it was demonstrated that the off-resonant field could substantially modify transport properties 21,46,47 , RKKY interaction 16,48 , excitonic dynamics, 49 and topological signatures of a two-dimensional lattice. 34,[50][51][52] Topological effects on various two-dimensional lattices in the presence of elliptically-polarized light were studied in Ref. [53].…”