Title: Negative Charge-Transfer Energy Materials

Date and Time: October 18, 2024 (Friday) 9:30-10:30 AM  

Venue: Meeting Room 309, Block A, Science and Education Building, Feicui Lake Campus  

Presenter: Dr. Zhao Liu  

Affiliation: Monash University, Australia  

Abstract:  

This presentation will delve into a relatively underexplored class of materials. Based on the ZSA classification, under low-energy excitation conditions, transition metal compounds can be classified into two extreme categories: Mott-Hubbard systems and charge-transfer systems. The former primarily involves the metal d orbitals, while the latter involves both the metal d orbitals and ligand p orbitals. In certain cases, these p orbitals can be projected onto d orbitals, reducing the system to a Mott-Hubbard type. Compared to these two well-studied material systems, research on negative charge-transfer energy materials remains relatively insufficient. Based on the concept of negative charge-transfer energy, this presentation will discuss its critical influence on two key aspects: 1) the nature of spin exchange interactions; and 2) the decisive impact on higher-order topological phases. Through this research, we aim to elucidate the following conclusions: 1) non-local molecular orbitals are ubiquitously present in such systems; and 2) charge ordering plays a crucial role in determining the topological properties of the material.  

Presenter Bio:

Dr. Zhao Liu graduated in 2018 from the National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China (USTC), with a focus on two-dimensional and topological materials. From 2019 to 2022, he served as a "Mozi" Young Scholar at USTC, focusing on the study of infinite-layer nickelate superconductors. Since 2023, he has been a Research Fellow at Monash University, Australia, continuing in-depth research on the physical properties of negative charge-transfer energy materials. To date, Dr. Liu has published over 30 academic papers, with his work as first author, co-first author, or co-corresponding author appearing in renowned journals such as PRL, PRB, Nano Letters, JACS, and AM.