Realization of intrinsically broken Dirac cones in graphene via the momentum-resolved electronic band structure

Abstract

A way to represent the band structure that distinguishes between energy-momentum and energy-crystal momentum relationships is proposed upon the band-unfolding concept. This momentum-resolved band structure offers better understanding of the physical processes requiring the information of wave functions in momentum space and provides a direct connection to angle-resolved photoelectron spectroscopy (ARPES) spectra. Following this approach, we demonstrate that Dirac cones in graphene are intrinsically broken in momentum space and can be described by a conceptual unit cell smaller than the primitive unit cell. This hidden degree of freedom can be measured by ARPES experiments as missing weight that is retrievable by investigating the effect of different polarized light. Having the energy-momentum relationship, we provide alternative understanding of the retrieved momentum intensity beyond the periodic-zone scheme, that is, the retrieved momentum intensity is assisted with the properties of final states, not from the Dirac cones directly. The revealed broken Dirac cones and momenta supplied by the lattice give interesting ingredients for designing advanced nanodevices.

A structure map for AB2 type 2D materials using high-throughput DFT calculations

“…17,18 It is worth mentioning that such discoveries of new 2D materials have been supported by the improvement in measurement technology and computational methods for theoretical calculations. For example, angle-resolved photoemission spectroscopy (ARPES), [19][20][21] X-ray photoelectron spectroscopy (XPS), 22,23 scanning tunneling microscopy (STM), 24,25 and atomic force microscopy (AFM) 26 have made a paradigm shift from research on bulk features in solids to investigation of surface science, where electronic structure calculations have been becoming indispensable tools to elucidate structures and the chemical and physical properties on the surfaces of solids.…”

Realization of a two-dimensional Weyl semimetal and topological Fermi strings

“…The edge state electronic structure was calculated by Green’s function technique, which computes the spectral weight near the edge of a semi-infinite system. To simulate the photoemission matrix element effects in the ARPES spectra, we consider a non-trivial structure factor in ab initio calculations 54 , 55 . To simulate this effect, we construct a unitary matrix U ( k ): where k is the momentum vector, r i is the real space coordinates of the i th atom in the original Bi/SnSe(S) unit cell.…”

Observation of 2D Weyl Fermion States in Epitaxial Bismuthene

“…The edge state electronic structure was calculated by the Green's function technique, which computes the spectral weight near the edge of a semi-infinite system. To simulate the photoemission matrix element effects in the ARPES spectra, we consider a non-trivial structure factor in ab initio calculations [65,66]. To simulate this effect, we construct a unitary matrix U (k ):…”