Strain engineering of WS2, WSe2, and WTe2

Abstract

We perform first-principles calculations to investigate the structural, electronic, and vibrational properties of WS₂, WSe₂, and WTe₂ monolayers, taking into account the strong spin orbit coupling. A transition from a direct to an indirect band gap is achieved for compressive strain of 1% for WS₂, 1.5% for WSe₂, and 2% for WTe₂, while the nature of the band gap remains direct in the case of tensile strain. The size of the band gap passes through a maximum under compressive strain and decreases monotonically under tensile strain. A strong spin splitting is found for the valence band in all three compounds, which is further enhanced by tensile strain. The mobility of the electrons grows along the series WS₂ < WSe₂ < WTe₂.