Control of the MoTe$_2$ Fermi Surface by Nb Doping

TL;DR

This study demonstrates that Nb doping effectively tunes the electronic structure of MoTe$_2$, inducing Lifshitz transitions and altering surface and bulk band properties, which can be exploited to access various electronic regimes.

Contribution

It provides combined theoretical and experimental evidence that Nb doping shifts the chemical potential in MoTe$_2$, enabling control over its Fermi surface and electronic phases.

Findings

Nb doping reduces bulk and surface band occupation by ~0.3 eV.

Multiple Lifshitz transitions are possible with small doping changes.

Surface band filling increases with alkali atom deposition.

Abstract

Ab initio calculations and angle-resolved photoemission experiments show that the bulk and surface electronic structure of Weyl semimetal candidate MoTe$_2$ changes significantly by tuning the chemical potential by less than 0.4 eV. Calculations show that several Lifshitz transitions can occur among multiple electron and hole Fermi pockets of differing orbital character. Experiments show that 18% Nb-Mo substitution reduces the occupation of bulk and (001) surface bands, effectively producing a chemical potential shift of $\approx 0.3$ eV. Orbital character and dimensionality of the bulk bands is examined by soft X-ray angle resolved photoemission with control of the excitation light polarization. The band filling at the surface is shown to increase upon deposition of alkali atoms. The results indicate that multiple regimes of electronic properties can be easily accessed in this versatile, layered material.