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Hysteresis is a history-dependent response of a system when subjected to an external perturbation. This phenomenon is ubiquitous in physics, biology, and even economics. In condensed matter, it underlies a large number of phase transitions, leading to everyday applications ranging from memory devices to functional polymers. In this talk, I will present our recent finding of an unconventional hysteretic transition in the charge density wave phase (CDW) of a quasi-2D compound, EuTe4. By combining transport, photoemission, diffraction, and x-ray absorption measurements, we observed that the hysteresis loop has a temperature width of more than 400 K, setting a record among crystalline solids. The transition has an origin distinct from known mechanisms, lying entirely within the incommensurate CDW phase of EuTe4 with no change in the CDW modulation periodicity. We interpret the hysteresis as an unusual switching of the relative CDW phases in different layers -- a phenomenon that is unique to quasi-2D compounds not present in purely 2D or strongly-coupled 3D systems.
Dr. Lv obtained his Ph.D. degree in 2018 from the Institute of Physics, Chinese Academy of Sciences under the supervision of Prof. Hong Ding and Prof. Tian Qian. He is currently a postdoc researcher at the Massachusetts Institute of Technology working with Prof. Nuh Gedik. Dr. Lv’s research interests lie in the understanding and manipulation of novel broken symmetry and topological quantum states in condensed matter physics.