Event

Quantum Materials Center Colloquium: The Rich Physics of a Square Lattice

Thursday, March 31, 2022
2:00 p.m.
1201 John S. Toll Physics Bldg and online
Roy Arunkumar
rakumar@umd.edu
https://umd.zoom.us/j/91301075848

The rich physics of a square lattice: correlations and topology in the Eu(Al,Ga)4 compounds

Jeffrey Lynn

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. In particular, the EuAl2Ga2 member of this series shows multiple non-collinear spin texture states below TN. One of these is likely a skyrmion state, as suggested by neutron diffraction and topological Hall effect measurements. I will discuss the possible relation between the incommensurate charge density wave (CDW) and the non-collinear spin textures in the centrosymmetric Eu(Al,Ga)4 series, when comparing the EuAl2Ga2 properties with those of the end compounds EuGa4 and EuAl4: a CDW is observed in EuAl2Ga2, but not it the EuGa4 analogue, where the magnetic order is just a collinear antiferromagnetic state. Remarkably, magnetization, quantum oscillations and ARPES measurements, together with band structure calculations, show evidence for topological Weyl nodal lines and a topological phase transition in EuGa4. 

Seminar also on Zoom
Meeting Link:  https://umd.zoom.us/j/91301075848