Seminar Date: Tuesday, January 28, 2025
Time: 11:00 AM PT
Location: 67-3111 & Zoom
Talk Title: An Electronic Structure Toolbox for Quantum Materials
Zoom recording (available for 30 days after the talk)
Abstract:
Understanding the fundamental nature of quantum phase transitions is essential to sustaining and advancing humanity’s information infrastructure. Access to the momentum-resolved electronic structure has arguably provided the most powerful information about the nature of unconventional quantum phases in a condensed matter framework. Here, I present a comprehensive research platform for quantum materials that vertically integrates prediction, experimental architecture, and metrological verification.
We apply this platform to Altermagnets, an emerging class of magnets beyond typical ferromagnets and antiferromagnets and whose nonrelativistic spin splitting (NRSS) of electronic bands holds both connections to unconventional superconductivity and transformative potential for energy-efficient electronics. By combining theory and experiment we uncover NRSS in a transition metal dichalcogenide, CoNb4Se8. We directly measure NRSS throughout the electronic structure using spin-resolved photoemission spectroscopy for the occupied bands and a newly developed technique, spin- and angle-resolved electron reflection spectroscopy, for the unoccupied states. Temperature-dependent measurements show the suppression of NRSS at the Néel temperature, providing the first direct evidence of an altermagnetic phase transition. The origins of the NRSS are corroborated by first-principles calculations and understood through a tight-binding model using a novel symmetry-constrained adaptive basis that captures global symmetries. This study establishes CoNb4Se8 as a prototypical g-wave altermagnet, and validates that an integrated theory-experiment framework is not only efficient but also adaptable to other phases of matter with distinct electronic signatures.
