Quantum Matter Seminar：Pseudogap and Kondo hybridization in Ce-based heavy fermion superconductors

Tuson Park 

Sungkyunkwan University, Korea

报告时间：2024年11月11日（周一）下午15:30

报告地点：紫金港校区段永平教学楼2号楼212报告厅

摘要：

In this paper, we propose a new electrical breakdown mechanism for exciton insulators in the BCS limit, which differs fundamentally from the Zener breakdown mechanism observed in traditional band insulators. Our new mechanism results from the instability of the many-body ground state for exciton condensation, caused by the strong competition between the polarization and condensation energies in the presence of an electric field. We refer to this mechanism as “many-body breakdown”. To investigate this new mechanism, we propose a BCS-type trial wave function under finite electric fields and use it to study the many-body breakdown numerically. Our results reveal two different types of electric breakdown behavior. If the system size is larger than a critical value, the Zener tunnelling process is first turned on when an electrical field is applied, but the excitonic gap remains until the field strength reaches the critical value of the many-body breakdown, after which the excitonic gap disappears and the system becomes a highly conductive metallic state. However, if the system size is much smaller than the critical value, the intermediate tunnelling phase disappears since the many-body breakdown happens before the onset of Zener tunnelling. The sudden disappearance of the local gap leads to an “off-on” feature in the current-voltage (I − V ) curve, providing a straightforward way to distinguish excitonic insulators from normal insulators.

报告人简介：

Tuson Park, Chair of the Department of Physics, Sungkyunkwan University, Korea, and also Director of the Center for Quantum Materials & Superconductivity. His research is centered on discovering and studying new quantum phases emerging under extreme conditions in strongly correlated electron systems. A variety of experimental techniques under extreme conditions have been developed to study the electrical, thermodynamic, and spectroscopic properties of the emergent quantum phases that appear near the absolute zero Kelvin (T=0 K). His research has resulted in the publication of 139 papers in the refereed journals, including 2 articles in Nature, 1 in Nature Physics, 4 in Nature Communications, 3 in PNAS, 15 in PRL, 3 in NPG Asia Materials, 20 in PRB, and 6 in Scientific Reports.