University of Minnesota
School of Physics & Astronomy

Quantum Materials Seminar

Tuesday, September 24th 2019
Speaker: Liang Wu, University of Pennsylvania
Subject: How many magnetic-field induced phase transitions in α−RuCl3?

Spin-1/2 moments in the antiferromagnetic Mott insulator α-RuCl3 are coupled by strongly anisotropic bond-dependent exchange interactions on a honeycomb lattice. Intense study of α- RuCl3 has been driven by the proposal that its low energy excitations may be adiabatically connected to the Majorana quasiparticles that emerge in the exact solution of the Kitaev spin liquid model. In my talk, I will present optical absorption measurements using terahertz spectroscopy and reveal several new features of the low-energy spectrum that evolves with a magnetic field. We find a few sharp absorption peaks upon cooling below the Neel temperature and shifts to lower frequency below 7 Tesla as long-range magnetic order is lost in a manner consistent with transitioning to a spin- disordered phase. I will also discuss how many magnetic-field induced phase transition in this system in various geometries with polarized THz light up to 17.5 T to address the nature of the spin-disordered phase.

Short Bio: Liang Wu got his B.S. in Physics from Nanjing University in 2010 and Ph.D in Physics at Johns Hopkins University in 2015. He was a postdoc fellow in Physics at University of California, Berkeley from 2016 to 2018 before joining the department of Physics and Astronomy at the University of Pennsylvania in July 2018. He has been using terahertz spectroscopy and ultrafast optics to study topological insulators, Weyl semimetals and quantum spin liquids. He received the McMillan Award for outstanding contribution in condensed matter physics from the University of Illinois (2019), the Army Research Office Young Investigator Program (YIP) Award (2019), and the Richard L. Greene Dissertation Award in Experimental Condensed Matter Physics by the American Physical Society (2017).

Faculty Host: Natalia Perkins

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