报告题目：Electronic structure evidence for charge nematic bond order in single unit cell thick iridate films

报 告 人：Changyoung Kim

报告时间：2026年7月9日 10：00

报告地点：物理楼W105会议室

内容摘要：Two-dimensional (2D) systems can exhibit physical properties that are markedly different from those of their three-dimensional (3D) counterparts, as reduced dimensionality can profoundly alter electronic behavior. Atomically thin materials further enable precise control and manipulation of physical properties. While many novel 2D systems are obtained by exfoliating van der Waals materials, an alternative and more conventional route is thin-film growth[1][2][3][4]. In this presentation, I will introduce our efforts to measure and control the electronic properties of one–unit-cell (UC)–thick films using epitaxial thin-film growth combined with in situ angle-resolved photoemission spectroscopy (ARPES). I will focus in particular on single-UC SrIrO₃ (SIO) films[5].A single-UC SIO film has the same crystal structure as a single layer of Sr₂IrO₄, a relativistic Mott insulator. Accordingly, single-UC SIO exhibits an electronic structure similar to that of Sr₂IrO₄, including a Mott-insulating state with short-range antiferromagnetic order. Remarkably, metallic states can be induced by epitaxial strain when SIO films are grown on substrates with different lattice constants. This strain-induced metallic state retains strong correlation effects and displays much sharper spectral features than those observed in Sr₂IrO₄, enabling detailed polarization-dependent ARPES measurements. Our polarization-dependent experiments [1] suggest that the ground state of single-UC SIO may host a charge nematic bond order. Preliminary STM results support the interpretation.

References:

1. B.M. Sohn et al., Nature Communications 12, 6171 (2021)

2. B.M. Sohn et al., Nature Materials 20, 1643 (2021)

3. J.R. Kim et al., Advanced Materials (2023)

4. E.K. Ko et al., Nature Communications (2023)

5. J. Y. Kim, in preparation

报告人简介：Prof. Kim received his Ph.D. in Applied Physics from Stanford University. After working at SSRL as a staff member, he took a faculty position at Yonsei University in the department of Physics. He moved to Seoul National University as a professor in the department of Physics and Astronomy as well as an associate director of the center for correlated electron systems. His expertise is in angle resolved photoelectron spectroscopy on correlated materials, including high temperature superconductors and topological materials. His recent research interest is focused on investigation of novel electronic phases, via in-situ ARPES, that can be realized in atomically thin films of correlated materials. In addition to the atomically thin film results, his notable accomplishments include observation of spin-charge separation and discovery of the role of orbital angular momentum in solids.