The control of Quantum states by First-principles investigation

Title

The control of Quantum states by First-principles investigation

Speaker

Xiang-Bo Xiao (Shaoyang University)

Time and Location

Friday, January 17, 2025, 16:30 – 17:30, R407, Research Building, North Campus

Abstract

In the condense matter, quantum systems exhibit extremely rich physical phenomena due to the multiple degrees of freedom coupling and competition among charge, spin, orbital, and lattice, making them an ideal platform for novel quantum phenomena under external field control. Firstly, we find through that when a biaxial compressive stress is applied on rutile CrO₂, the density of states at the Fermi level decreases with the in-plane compressive strain, there is a structural phase transition then appears an electronic phase transition. Further analysis shows that this structural transition, accompanying the tetragonal symmetry breaking, is induced by the stress-driven distortion and rotation of the oxygen octahedron of Cr, and the half-metal-semiconductor transition originates from the enhancement of the crystal field splitting due to the structural change. Then, we find that one epitaxial TcO₂ bilayer on rutile TiO₂(001) substrate is an antiferromagnet-like narrow-gap semiconductor, and its electronic and magnetic properties can be manipulated through electric field. When electric field reaches 0.03 V/Å, it transits to a half-metallic ferrimagnet with 100% spin polarization. Finally, we report the cascade of Landau quantization in a strained type-II Dirac semimetal NiTe₂ with spectroscopic-imaging scanning tunneling microscopy. First-principles calculations demonstrate that the multiple LLs attest to the remarkable lifting of the valley degeneracy of TSS by the in-plane uniaxial or shear strains. Our findings pave a pathway to tune multiple degrees of freedom and quantum numbers of TMDs via strain engineering for practical applications such as high-frequency rectifiers, Josephson diode and valleytronics.

Bio

Dr. Xiang-Bo Xiao is currently working in Department of Physics, Shaoyang University. She has done her postdoctoral research on the group of Prof Bang-Gui Liu, in the Institute of Physics, Chinese Academy of Sciences. In 2020 spring, Dr Xiao obtained her Ph.D. in theoretical physics from the Institute of Physics, Chinese Academy of Sciences. Her main research focuses on designing and controlling the electronic and magnetic properties of materials.