清华大学材料科学与工程研究院《材料科学论坛》

学术报告

时间：2018年6月8日（星期五） 15:00

地点：清华大学逸夫技术科学楼A512房间

联系人：南策文老师 62773587

学术报告1：

题目：Designer Quantum Matter: From ‘ferroelectric’ metal to magnetic 2D electron liquid

报告人：Prof. Jak Chakhalian（Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, USA）

报告摘要：

Complex oxides with correlated electrons are a class of materials characterized by multiple competing and nearly degenerate ground states due to interactions that create a subtle balance to define the lowest energy state. This notion leads to a wide diversity of intriguing properties ranging from high Tc superconductivity to exotic magnetism and spin and orbit entangled phenomena. By utilizing the bulk properties of these materials as a starting point, interface between different classes of correlated oxides combined with geometrical lattice engineering offer a unique opportunity to break the fundamental symmetries of bulk and devise novel many-body and topological phases. These designer structures with enhanced electronic correlations, spin-orbit coupling, and lattice geometries supporting frustrated magnetic interactions can serve as a remarkably fertile ground for unusual quantum states of matter.
Utilizing our recent advances in complex oxide growth with the atomic layer precision, we can now combine layers of materials with distinct and often antagonistic order parameters to create novel artificial quantum materials. The broken lattice symmetry, strain, and altered chemical and electronic environments at the interfaces then provide a unique platform to manipulate this subtle balance and enable novel quantum states. Understanding of these phases, however, requires detailed microscopic studies of the heterostructure properties. To illustrate these challenges and opportunities, I will address the issues of manipulating magnetic interactions on the nanoscale and understanding the behavior of spins in the ultimate 2D limit, modulated carrier density, and orbital polarization. I will demonstrate the examples of realization of a magnetic 2D electron liquid and ‘ferroelectric’ 2D metal.

报告人简介：
Prof. Chakhalian obtained his Ph.D degree from The University of British Columbia, Vancouver, Canada, 2002. After that, He joined TRIUMF, National Canadian Research Centre, Vancouver, Canada from 2002 to 2003, and Max Planck Institute for Solid State Research, Stuttgart, Germany from 2004 to 2006 as a postdoctoral fellow. He is currently Claud Lovelace Endowed Professor of Physics of Rutgers University, Piscataway, NJ.

学术报告2：

题目：Spin direction controlled electronic band structure in two dimensional ferromagnetic materials

报告人：Prof. Zhicheng Zhong

报告摘要：

Manipulating physical properties using the spin degree of freedom constitutes a major part of modern condensed matter physics and is very important for spintronics devices. Using the newly discovered two dimensional van der Waals ferromagnetic CrI3 as a prototype material, we theoretically demonstrated a giant magneto band structure (GMB) effect that a change of magnetization direction significantly modifies electronic band structure. Our density functional theory calculations and model analysis reveal that reorienting the magnetic moment of CrI3 from out-of-plane to in-plane causes a direct-to-indirect bandgap transition, inducing a magnetic field controlled photoluminescence. Our results also show a significant change of Fermi surface with different magnetization directions, leading to giant anisotropic magnetoresistance. What is more, the spin reorientation is found to modify the topological states. Given that a variety of properties are determined by band structures, our predicted GMB effect in CrI3 opens a new paradigm for spintronics applications. [1]

[1] P. Jiang, L. Li, Z. Liao, Y. Zhao, and Z. Zhong, Nano Letters (2018 In press)

报告人简介：

Prof. Zhicheng Zhong obtained his Bachelor degree from Shanghai jiaotong University, Master degree from Peking University, and Ph.D degree from Twente University in 2011. Then, he was a postdoc in Prof. Karsten Held’s group of Vienna University of Technology, and Humboldt postdoc research fellow in Wuerzburg University, and Max Planck postdoc research fellow in Max Planck institute of solid state physics. He was awarded national 1000 young talent, 100 talent of Chinese Academy of Sciences, and joined Ningbo Institute of Materials Technology and Engineering in 2017. His research is focused on complex oxide interfaces and two dimensional magnetic materials.