Two-dimensional MX Dirac materials and quantum spin Hall insulators with tunable electronic and topological properties

Abstract

We propose a novel class of two-dimensional (2D) Dirac materials in the MX family (M=Be, Mg, Zn and Cd, X = Cl, Br and I), which exhibit graphene-like band structures with linearlydispersing Dirac-cone states over large energy scales (0.8~1.8 eV) and ultra-high Fermi velocities comparable to graphene. The electronic and topological properties are found to be highly tunable and amenable to effective modulation via anion-layer substitution and vertical electric field. The electronic structures of several members of the family are shown to host a Van-Hove singularity (VHS) close to the energy of the Dirac node. The enhanced density-of-states associated with these VHSs could provide a mechanism for inducing topological superconductivity. The presence of sizable band gaps, ultra-high carrier mobilities, and small effective masses makes the MX family promising for electronics and spintronics applications.

Structures and electronic properties of functional molecules on metal substrates: From single molecule to self‐assemblies

“…To achieve calculations with high accuracy, the exchange‐correlation functionals and van der Waals corrections need to be improved with better descriptions on metal–organic interactions. In recent years, there are many efforts on database‐driven high‐throughput calculation 172,173 and machine learning, 174 which are the promising computational techniques in material sciences 175 . The development of the computational technology will contribute to the design of molecular self‐assembly with novel properties and their further applications.…”

Quantum phase transitions from competing short- and long-range interactions on a $π$-flux lattice

“…The resulting linear dispersion relation leads to many exotic physical phenomena. Besides the wellknown graphene, various 2D Dirac materials have been predicted and discovered experimentally up to now [9][10][11][12][13][14][15][16][17].…”

Switchable large-gap quantum spin Hall state in two-dimensional MSi$_2$Z$_4$ materials class

“…A common approach to realize the QSH state is to reduce the thickness of three-dimensional (3D) Z 2 topological insulators to drive a 3D to 2D crossover and a band inversion in the surface states. This method has successfully predicted the QSH state in thin films of Z 2 topological insulators [11,12,[23][24][25][26]. This approach for realizing the QSH state, however, remains challenging since it requires complex fine-tuning of either quantum well structure or film thickness to generate an inverted hybridization gap in the surface spectrum [11,12,[23][24][25][26][27][28][29].…”

“…This method has successfully predicted the QSH state in thin films of Z 2 topological insulators [11,12,[23][24][25][26]. This approach for realizing the QSH state, however, remains challenging since it requires complex fine-tuning of either quantum well structure or film thickness to generate an inverted hybridization gap in the surface spectrum [11,12,[23][24][25][26][27][28][29]. In the process, materials properties are often modified, leading to complicated electronic structures and quenching the quantized spin Hall conductance.…”