学术报告（2025年11月7日10:00）：Exotic Surface Properties of Delafossite PdCoO2 and PdCrO2

主 持 人：谢涛副教授

报告摘要：Delafossite metals ABO2 are known for their rich properties [1] and potential for realizing directional ballistic transport. This talk focuses on the surface properties of PdCoO2 and PdCrO2. First, I will report on the STM findings from their oxide-terminated surfaces [2,3], particularly on a rarely observed short-range charge order formed on the CrO2-terminated surface of PdCrO2 that, owing to its fragility, can only be captured by imaging at extremely low-currents [3]. Our calculation results suggest that surface charge disproportionation is the underlying mechanism. As for the Pd surfaces, both exhibit clear quasiparticle interference signals in their pristine form. However, when the Pd surface of PdCrO2, which can be regarded as a 2D metal, is adsorbed with hydrogen, a tiling structure consisting of closely packed hydrogen clusters is formed. This arrangement of hydrogen also leads to strong electronic localization [4], as well as extremely long-lived vibrational modes.

1. P. Mackenzie, The properties of ultrapure delafossite metals, Rep. Prog. Phys. 80, 032501 (2017).
2. M. Yim, D. Chakraborti, L. C. Rhodes, S. Khim, A. P. Mackenzie, and P. Wahl, Quasiparticle interference and quantum confinement in a correlated Rashba spin-split 2D electron liquid, Sci. Adv. 7, eabd7361 (2021).
3. M. Yim et al., Avoided metallicity in a hole-doped Mott insulator on a triangular lattice, Nat. Commun. 15, 8098 (2024).
4. M. Yim, Y. Zheng, O. R. Armitage, D. Chakraborti, C. J. Wells, S. Khim, A. P. Mackenzie, and P. Wahl, Adsorbate-induced formation of a surface-polarity-driven nonperiodic superstructure, Commun. Mater. 6, 128 (2025)

个人简历:严智明（Chi Ming Yim）教授2012年在伦敦大学学院（University College London）获得博士学位，随后在伦敦大学学院及圣安德鲁斯大学（University of St Andrews）从事博士后研究工作。2020年加入上海交通大学李政道研究所，任青年学者/长聘副教授，领导低温扫描隧道显微镜课题组，致力于在原子尺度上研究强关联电子材料中的奇异物理现象。截至目前，严智明教授已在Nature Materials, Nature Communications, PNAS 及 PRL等期刊发表论文39篇。