Materials Science Research Lecture

***Refreshments at 3:45pm in Noyes lobby

Abstract:

Topological materials have been at the forefront of condensed matter research for more than a decade, and continue to reveal novel physics. More recently, correlated topological materials have added a new level of complexity to our understanding of emergent phenomena in quantum materials. Taking a look back of some "old" compounds with the lens of topology is one way of finding such new physics. In this talk, I will revisit the class of Eu-based square lattice compounds Eu(Al,Ga)4, where complex magnetic order was first discovered several years ago, and a possible new skyrmion state revealed more recently in EuAl2Ga2. In addition to EuAl2Ga2, I will focus on the EuGa end compound in this series. Experimental and theoretical evidence points to Weyl nodal rings and a topological phase transition induced by magnetization tuning with applied magnetic field. Remarkably, EuGa4 shows very large magnetoresistance (> 2*105 % at 14 T), more than two orders of magnitude larger than other magnetic Weyl semimetals. We developed a theoretical model that accounts for the large non-saturating MR as a direct consequence of the Weyl nodal rings. If time permits, I will contrast the properties of Eu(Al,Ga)4 with another square net Eu antiferromagnet, EuRhAl4Si2, where the Eu local moments induce a small moment on Si. Overall, the different classes of Eu compounds underscore the complex magnetism even in the absence of crystal field anisotropy.

More about the Speaker:

Emilia Morosan is a Professor of Physics and Astronomy and the Director of the Rice Center for Quantum Materials (RCQM) at Rice University. She joined Rice in 2007, after a postdoc in the Chemistry Department at Princeton University. Prof. Morosan received her PhD in Physics from Iowa State University in 2005. Her research focuses on quantum materials with emergent properties, such as superconductivity and density waves, Kondo materials, unconventional topological fermions, complex structures with 2D transition metal dichalcogenides, and more. Morosan was elected Fellow of the American Physical Society (APS) in 2018 and has acted as APS DMP executive committee member-at-large from 2014 to 2017. Her work has been recognized by several awards, including the Presidential Early Career Award for Scientists and Engineers (PECASE), Moore Foundation EPiQS Synthesis Investigator, Humboldt Foundation Fellowship for Advanced Researchers. She was recently selected as one of the 2024 DOD Vannevar-Bush Faculty Fellows.