Speaker
Jinlong Zhu
Physics Department, Southern University of Science and Technology
Date＆Time
2022.01.15（Sat）PM 14:00
Location
Aoqing Tang Building B521
Tencent Meeting ID：831-386-532
Abstract
Researchers show great interests in two-dimensional crystals recently, as their thickness-dependent electronic and optical properties. Compared with other tuning methods, there are no additional impurities introduced by hydrostatic pressure, thereby it is a pure and clean approach. The unique electronic structure and crystal structure driven by external pressure in transition metal tellurides (TMTs) can host unconventional quantum states.. This talk including three parts: 1) As the enforcement of layer interaction, an electronic and a crystal phase transition were revealed at ~5 GPa and ~16 GPa, respectively in bilayer MoS2, while no phase transition in monolayer. The electronic phase transition at ~5 GPa is supposed to be a direct interband changing to an indirect Λ-K interband transition, and the new structure shown at ~16 GPa is not metallized and supposed to be a transformation from stacking faults due to layer sliding like 2Hc to 2Ha; 2) Due to the proper excess V atoms into VSe2 layers, we observed pressure-induced high intensity signal of CDW increasing to room temperature around 7.6-9.1 GPa in V1.13Se2. The phase transitions of room temperature are from a metal state with P-3m1 structure and the higher c/a ratio at P < 7.6 GPa, to a CDW state with P-3m1 structure and the lower c/a ratio at 9.1 GPa < P < 14.6 GPa, and finally to another metal state with C2/m structure at P > 16 GPa; 3) Discovery of pressure-induced phase transition at ~ 2 GPa, and dome-shaped superconducting phase in van de Waals layered NbIrTe4. The highest Tc was ~5.8 K at pressure of ~16 GPa, where the interlayered Te-Te covalent bond formed simultaneously derived from the synchrotron diffraction data. Strikingly, we found an anisotropic transport in the vicinity of the superconducting state, suggesting the emergence of a “stripe”-like phase. The dome-shaped superconducting phase and anisotropic transport are possibly due to the spatially modulated interlayer Josephson coupling strength.
