Strongly correlated oxides with a broken symmetry could exhibit various phase transitions, such as superconductivity, magnetism and ferroelectricity. Since the first observation and definition of magnetoelectric effect in 1888 and 1894, people have taken over 120 years to discover magnetoelectric materials for applications in miniature electromagnetic systems. However, restricted by the symmetry requirement, only limited materials show magnetoelectric coupling. These natural crystals gradually meet the bottleneck for future nanoscale integrated devices. It seems that artificial crystals by accurately atomic assembly, e.g. superlattice, provide bigger space for the design of symmetry and magnetoelectric effect that do not have in natural materials.
In this presentation, I will introduce that Ruddlesden-Popper antiferromagnetic Sr2IrO4 and perovskite paraelectric (ferroelectric) SrTiO3 (BaTiO3) are selected to epitaxially fabricate superlattices for symmetry engineering. An emergent magnetoelectric phase transition is achieved in Sr2IrO4/SrTiO3 superlattices with artificially designed ferroelectricity, where an observable interfacial Dzyaloshinskii-Moriya interaction driven by non-equivalent interface is considered as the microscopic origin. I will also show that room-temperature magnetoelectric coupling is possible by efforts on materials engineering such as graded strain, element replacement, interfacial atomic assembly, etc. This artificial symmetry engineering provides a general strategy to design quantum phases and orderings in correlated electron systems.
Prof. Jinxing Zhang graduated from department of applied physics at the Hong Kong Polytechnic University in 2009, under the supervision of Profs. Helen Chan and Jiyan Dai. Then he worked as a post-doctoral scholar at the University of California, Berkeley between 2009 and 2012 in Prof. Ramamoorthy Ramesh's group. Prof. Zhang has been in Department of Physics at Beijing Normal University as a full professor since 2012. The ultimate goal of his group is the artificial control of symmetries (time-reversal, space-inversion, gauge ones) in strongly correlated oxides for emergent quantum phenomena and functionalities. Recently, he has taken great efforts on exploring the potential applications of those fundamental discoveries on Beyond-CMOS devices. He published over 100 peer-reviewed papers including those in Nature Series, Physical Review Letters, Advanced Materials, etc. as corresponding author. In 2022, he was awarded a Distinguished Young Scholars Fund by NSFC.
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