Title: Coherentterahertz(THz) dynamics of collective excitations in a Weyl charge densitywave
Understandingthe fundamental collective excitations of an emergent many-bodyinteracting system has been a crosscutting theme throughout many branchesof physics. Key questions about the dynamics of these excitations in thepresence of both strong correlations and topology are currently drivingnumerous major research efforts in quantum materials. One such material is(TaSe4)2I - a Weyl semimetal that undergoes chargedensity wave (CDW) ordering below 260K. I will discuss two of our recentexperiments using nonlinear light-matter interaction in the terahertz(THz)range to directly probe the dynamics of the collective excitationsof (TaSe4)2I.I will first show how upon transient photoexcitationat low temperatures, (TaSe4)2I strikingly emitscoherent, narrow-band THz radiation. The frequency, polarization andtemperature-dependence of the emitted radiation imply the existence of a phasonthat acquires mass by coupling to long-range Coulomb interactions, giving adirect measurement of the Anderson-Higgs mechanism. Second, I willshow our recent results using THz pump, IR Kerr probe spectroscopyon (TaSe4)2Ito highlight how THz-driven phononscan induce a dynamic optical Kerr rotation in this otherwise time-reversalinvariant system. I will briefly discuss both these results in the context ofthe predicted axion electrodynamics in (TaSe4)2I.
Ref: S. Kim,Y.Lv, …., F. Mahmood. “Observation of a massive phason in a charge density waveinsulator”. Nature Materials 22, 429-433 (2023).
Host: Paglione
The seminar is also on Zoom, Invite Link: https://umd.zoom.us/j/94343757284
Refreshments 1:30pm 1117 Toll Physics Bldg.