DCMP Seminar: Kurt Hingerl

Department of Condensed Matter Physics invites you to lecture

Kurt Hingerl (Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Austria):
Observation of entangled electron-zone boundary phonon states with transient spectroscopic ellipsometry

Silicon has three optical phonons. These phonons remain inaccessible with linear optics. Here we demonstrate that time-resolved pump-probe spectroscopic ellipsometry enables the detection of optical phonon responses at both the Brillouin-zone center and edge. Using pump pulses with photon energies below the indirect bandgap of silicon, we leverage twophoton absorption to induce sub-bandgap excitation. Transient optical effects were probed in the 1.9-3.6 eV spectral range with pump-probe time delays from 50 fs to 4.5 ns. We observed distinct features: a structure at the E1 critical point persisting for 4.5 ns; longitudinal optical phonons with an energy spacing of 57±9 meV, lasting approximately 300 fs; and twophonon replicas, exhibiting a spacing of 81±7 meV.

This lecture was supported by the project QM4ST (Quantum materials for applications in sustainable technology), reg. no. CZ.02.01.01/00/22_008/0004572, cofunded by the ERDF from the Programme Johannes Amos Commenius, call Excellent Research.