Insulator–metal transition in 1T′-MoS2 under uniaxial strain

• Insulator–metal transition (IMT) occurs in 1T′-MoS2 stretched uniaxially.
• Critical strain for IMT strongly depends on its orientation and nature.
• IMT is due to strained bonds in Mo zigzag chains.
• Tuning of critical electric field for topological phase transition by strain.

First principles calculations have been performed to investigate the electronic properties of 1T′-MoS2 under uniaxial strain. Insulator–metal transition (IMT) occurs when 1T′-MoS2 is stretched uniaxially. For strain perpendicular to the zigzag chains of Mo atoms (ϵxϵx), the critical strain for the IMT is 3.0%, while it reaches 4.8% for strain along the y   direction. The IMT is due to the dropping of the state of the conduction band at the X point (CX) in the Brillouin zone, which is formed by the dx2−y2dx2−y2 orbitals of Mo atoms in the stretched Mo–Mo bonds and shows antibonding character. The x projection of the Mo–Mo bonds is rather larger than their y   projection, leading to the much smaller critical ϵxϵx for the IMT. In comparison with 1T′-MoS2 under biaxial strain (ϵbiϵbi), although the CX state drops more rapidly than that under x   strain, the critical ϵbiϵbi is even larger than the critical ϵxϵx, which is because the larger structural distortion under biaxial strain also induces great dropping of the valence band maximum. Moreover, uniaxial strain may be used for fine tuning of the critical electric field for the topological phase transition in 1T′-MoS2, which increases monotonically as a function of the strain.