Surface band characters of the Weyl semimetal candidate material MoTe2 revealed by one-step angle-resolved photoemission theory

Abstract

The layered two-dimensional material MoTe 2 in the T d crystal phase is a semimetal which has theoretically been predicted to possess topologically nontrivial bands corresponding to Weyl fermions. Clear experimental evidence by angle-resolved photoemission spectroscopy (ARPES) is, however, lacking, which calls for a careful examination of the relation between ground state band structure calculations and ARPES intensity plots. Here we report a study of the near-Fermi-energy band structure of MoTe 2 (T d ) by means of ARPES measurements, density functional theory, and one-step-model ARPES calculations. Good agreement between theory and experiment is obtained. We analyze the orbital character of the surface bands and its relation to the ARPES polarization dependence. We find that light polarization has a major effect on which bands can be observed by ARPES. For s-polarized light, the ARPES intensity is dominated by subsurface Mo d orbitals, while p-polarized light reveals the bands mainly derived from Te p orbitals. Suitable light polarization for observing either an electron or hole pocket are determined.

Assessing Nontrivial Topology in Weyl Semimetals by Dichroic Photoemission

“…The one-step model of photoemission calculations as implemented in the SPR-KKR band structure software package [18], based on Green's function and multiple scattering spin-density matrix formalism, properly includes all the matrix element effect related phenomena. This fully relativistic method gives access to a photoemission signal with an accurate angular variation of ARPES spectral weight caused by an experimental geometry, photon energy, and polarization state or surface termination [19][20][21][22]. In addition, an imaginary potential term V 0i is added to the singleparticle cell potential to simulate lifetime effects in the initial state.…”

Towards Robust Dichroism in Angle-Resolved Photoemission

“…The package takes into account sample termination and accurately represents all the photoelectron transition matrix-related phenomena, resulting in highly accurate photoemission spectra simulations. The versatility of SPR-KKR in modeling physical systems has been demonstrated not only on TMDCs [22,30,31], but also on simple systems such as Pd [32], heterostructures [33] or topologically non-trivial systems such as TaAs [32]. By nature of the multiple scattering formalism, a highly accurate multiply-scattered time-reversed low energy electron diffraction (TR-LEED) [25,26] is the default final state choice.…”