题目：Nature of insulating states in low-dimensional electron systems

主讲嘉宾：Prof. Jun-Hyung Cho （Department of Physics, Hanyang University）

时间： 6月12日（周二）上午9:00—11:00

地点：师昌绪楼403会议室

报告简介：

1D and 2D electronic systems feature interacting quasi-particles that are associated with their charge, spin, orbital, and lattice degrees of freedom. As a consequence of such interactions, various macroscopic quantum coherence such as charge density waves (CDW), magnetic ordering, Mott physics, or topological states can be produced. In this talk, I will present our recent first-principles density-functional theory (DFT) studies of low-dimensional electron systems that exhibit competing charge-lattice, spin-lattice, and electron-electron interactions. As for the 1D electron systems, we discuss the ground state of the metallic atom wires containing dangling-bond (DB) electrons, fabricated by partially hydrogenating the GaN(10-10) and ZnO(10-10) surfaces. We find that the DB wires in GaN(10-10) have the anfiferromagnetic ground state, while those in ZnO(10-10) have the CDW state [1]. We also discuss the phase transition in indium nanowires on Si(111), the origin of which has long been controversial [2]. For the 2D electron systems, I not only discuss the Mott vs Slater mechanisms for the observed insulating states in Sn overlayer on Si(111) and Ge(111) [3], but also present the intriguing feature of CDW in monolayer TaS2 which involves the interplay of the charge, lattice, orbital, and spin degrees of freedom [4].

[1] S. W. Kim et al., Phys. Rev. Lett. 118, 239601 (2017); Phys. Rev. B 96, 235416 (2017).
[2] H. J. Kim et al., Phys. Rev. Lett. 110, 116801 (2013); Zhang et al., Phys. Rev. Lett. 113, 196802 (2014).
[3] J. H. Lee et al., Phys. Rev. Lett. 111, 106403 (2013); Phys. Rev. B 90, 125439 (2014).
[4] S. Yi et al., Phys. Rev. B 97, 041413(R) (2018).

主讲嘉宾简介：

Prof. Jun-Hyung Cho is currently a Professor of Physics Dept. at Hanyang University. He received a B.S. degree in Physics Dept. from Hanyang University in 1983, and a M.S. degree in theoretical condensed matter physics from Seoul National University in 1986. From Pohang University of Science and Technology, he received PhD degree in theoretical condensed matter physics. Then he worked as postdoctoral researcher and research associate at several different institutions, including Fritz-Haber-institut, Oak Ridge National Laboratory, National Renewable Energy Laboratory, and University of Texas at Austin. In 2003, he joined Hanyang University.