In this work, we utilize XUV-SHG spectroscopy to investigate the polar metal phase of LiOsO₃, where the coexistence of polarity and metallicity is unexpected since the itinerant conducting electrons in metals are expected to screen out long-range electrostatic forces that typically stabilize a permanent polarization. This is one of the first uses of nonlinear X-ray spectroscopy to investigate a material across a phase transition. A sensitivity to broken inversion symmetry appears above the Li K-edge, with theory showing how the spectrally-resolved SHG varies with Li-displacement. As the first demonstration of XUV-SHG spectroscopy around a phase transition, these results pave the way for using nonlinear XUV methods to investigate broken symmetry from an element-specific perspective.

Congratulations to Emma for her first author paper, and Angelique and Can for their first paper in the group. Also, we are excited for Clarisse’ first paper, who contributed to this work during her NSF-REU visit last summer.

This work was done in collaboration with researchers from LBNL, UC San Diego, Argonne National Laboratory, Penn State, and the University of Tokio. The experiments were conducted at the free-electron laser facility SACLA in Japan.

Our paper appeared in Nano Letters (open access) and was selected as cover featured article:
https://pubs.acs.org/doi/10.1021/acs.nanolett.1c01502

We had our first retreat as a group and went hiking two days in Yosemite National Park. Giant Sequoias, Glacier Point and several waterfalls were explored. Despite 103 degrees, it has been a very memorable retreat.

Michael was awarded the 2021 Fresnel Prize by the European Physical Society – Quantum Electronics and Optics Division in the “fundamental research” category “for outstanding contributions to the field of ultrafast condensed-matter science and for the application of linear and nonlinear X-ray spectroscopies to the investigation of quantum phenomena“. The Fresnel Prize is awarded every 2 years to a researcher 35 years or younger, one each in the areas of fundamental and applied research. The award ceremony took place virtually during the CLEO Europe conference.

College of Chemistry News Release:
https://chemistry.berkeley.edu/news/michael-zuerch-receives-award-quantum-electronic-and-optics-research