Strain-induced half-valley metals and topological phase transitions in M Br2 monolayers (M =Ru ,Os )
Abstract
The target of valleytronics developments is to manipulate the valley degree of freedom and utilize it in microelectronics as charge and spin degrees of freedom. Based on first-principles calculations, we demonstrate that M Br2 (M =Ru ,Os ) monolayers are intrinsically ferrovalley materials with large valley polarization up to 530 meV. Compressive strain can induce phase transitions in the materials from ferrovalley insulators to complete valley-polarized metals, called half-valley metals, in analogy to the concept of half metals in spintronics. With the increase of the strain, the materials become Chern insulators, whose edge states are chiral-spin-valley locking. The phase transition is caused by sequent band inversions of the dx y/dx2−y2 and dz2 orbitals at K − and K + valleys, analyzed based on a strained k .p model. Our work provides a pathway for carrying out low-dissipation electronics devices with complete spin and valley polarizations.
- Publication:
-
Physical Review B
- Pub Date:
- October 2021
- DOI:
- 10.1103/PhysRevB.104.165427
- Bibcode:
- 2021PhRvB.104p5427H