Physics & Astronomy Colloquium: Dr. Veronika Sunko, UC Berkeley


Location: 127 Nieuwland Science Hall (View on map )

Shedding Light on Symmetry

Dr. Veronika Sunko
UC Berkeley

The main goal of condensed matter physics is uncovering, understanding, and controlling novel phases of matter. Symmetry plays a key role in defining these phases, providing a framework for theoretical description of observable phenomena. Accurate experimental determination of symmetry is therefore crucial. In this talk, I introduce linear magneto-birefringence, a new technique I developed, capable of revealing magnetic symmetries inaccessible to standard Methods.

Correctly identifying magnetic symmetries is particularly important in materials with coupled electronic and magnetic degrees of freedom, in which magnetism can cause drastic changes to electronic states, including protecting exotic topological phases. EuIn2As2 is a prominent example of the latter: it has been identified as a prime candidate to host the elusive axion state, exhibiting a quantized magneto-electric effect. However, despite intense experimental efforts, no direct evidence for topology in EuIn2As2 is available, motivating a reexamination of standard assumptions. I will illustrate the effectiveness of linear magneto-birefringence as a probe of symmetry on EuIn2As2, where I was able to uncover the symmetry of two magnetic phases, and relate it to topological properties.

I will further discuss my plans to apply linear magneto-birefringence and related techniques to a new class of materials, so-called altermagnets. Here, exciting theoretical predictions of exotic phenomena have outpaced experimental validation. Linear magneto-birefringence is the perfect tool to detect altermagnetism, which can remain hidden from other probes. Combining it with spectroscopic and transport tools will enable me to test current theories and stimulate new ones. More broadly, this symmetry-sensitive toolkit is applicable to a wide range of material classes, and will shed light on them in the years to come.

Hosted by Prof. Janko