Linear and nonlinear optical dynamic responses in the Dirac semimetal NiTe2

by Prof. Jingbo Qi (齐静波） (University of Electronic Science and Technology of China)

Friday 29 May 2026, 10:00 → 11:00 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Host: Prof. Tao Dong

Venue: TDLI Meeting Room N400

Tencent meeting link: https://meeting.tencent.com/dm/VazMuVKC0M2d  Meeting ID: 141767202, no password

 

Abstract:

Using ultrafast optical spectroscopy, researchers studied quasiparticle dynamics in NiTe2. Around 60 K, anomalous optical responses appear, consistent with transport measurements. At this temperature, a phonon-assisted electron-hole recombination process shows unusual behavior, with changes in phonon energy and lifetime. These anomalies stem from a shift in the phonon mode caused by an abrupt modification of the electronic structure near the Fermi surface, indicating emergence of Lifshitz transition. Meanwhile, intense terahertz pulses induce nonlinear responses in this centrosymmetric material. The terahertz vector potential creates a transient effective magnetic point group, breaking symmetry and enabling second-harmonic generation—a process beyond conventional third-order nonlinearities. This yields a significant second-order susceptibility, confirmed by polarization-dependent signals.

 

Biography:

Jingbo Qi, a professor at the University of Electronic Science and Technology of China. He got his Ph.D. from Vanderbilt University (USA). He was ever a postdoctoral associate in the National High Magnetic Field Laboratory and Los Alamos National Laboratory, respectively. His main research interest focuses on using the ultrafast optical spectroscopy and terahertz spectroscopy to study the dynamical properties in various systems such as topological materials and strongly correlated materials.