The ground state of monolayer $1T^{\prime }\text{−}{\mathrm{WTe}}_2$ has been a target of intensive debate on whether or not it is a two-dimensional topological insulator (2D TI) associated with exciton formation. We investigated the band structure of an epitaxial monolayer $1T^{\prime }\text{−}{\mathrm{WTe}}_2$ film grown on graphene/SiC(0001) in a wide temperature range of $T=40-400\mathrm{K}$ by angle-resolved photoemission spectroscopy (ARPES). We observed an electron band above the Fermi level ($E_{\mathrm{F}}$) slightly away from the $\mathrm{\Gamma }$ point, together with four hole bands below $E_{\mathrm{F}}$ just at the $\mathrm{\Gamma }$ point. This signifies an indirect band gap exceeding 0.1 eV in support of the 2D-TI phase with the inverted band structure. We uncovered an unexpectedly large downward shift of valence bands upon cooling, accompanied with an upward shift of the conduction band. Comparison of the ARPES-derived band structure with first-principles band calculations suggests that the observed band shift is ascribed to the systematic local atomic distortion of tungsten atoms, which should be incorporated into the interpretation of unusual transport properties of $1T^{\prime }\text{−}{\mathrm{WTe}}_2$.

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• Electronic structure
• Topological insulators
• Angle-resolved photoemission spectroscopy
• Molecular beam epitaxy