Thema der Dissertation:
Ultrafast Terahertz Control of Structural and Charge Carrier Dynamics in Emerging Semiconductors
Ultrafast Terahertz Control of Structural and Charge Carrier Dynamics in Emerging Semiconductors
Abstract: Advances in high-field terahertz (THz) generation over the past 15 years have enabled ultrafast control of semiconductor properties with high efficiency and selectivity. This thesis focuses on two aspects of THz-driven material control on picosecond timescales: the direct driving of lattice vibrations (phonons) to coherently modulate the crystal structure and the rapid acceleration of charge carriers.
First, we establish quartz as a novel electro-optic detector material for full amplitude, phase, and polarization characterization of intense THz pulses. This development supports ongoing efforts to drive circular phonons and prepare states of phonon angular momentum. We then demonstrate that intense THz pulses can nonlinearly excite octahedral twist modes of the inorganic sublattice in hybrid MAPbBr3 and all-inorganic CsPbBr3 lead halide perovskites (LHPs). Using THz-induced Kerr effect spectroscopy, we show that these Raman-active phonons at ~1 THz dominate the lattice contribution to the nonlinear THz polarizability at low temperatures. Since these lattice modes strongly couple to the electronic bandgap, this finding demonstrates the potential for phonon-driven ultrafast bandgap control in LHPs. Finally, we show that intense THz pulses can quench the total photoluminescence (PL) emission in the wide-bandgap semiconductor ZnTe by more than 60%. Using optical pump-THz probe techniques, we find that the THz field reduces the carrier lifetime, suggesting enhanced non-radiative recombination as the origin of the THz-induced PL quenching.
Together, these results demonstrate the potential of intense THz pulses to control structural and charge carrier dynamics in conventional and emerging semiconductors, enabling ultrafast control of the electronic bandgap, carrier lifetime, and PL emission.
First, we establish quartz as a novel electro-optic detector material for full amplitude, phase, and polarization characterization of intense THz pulses. This development supports ongoing efforts to drive circular phonons and prepare states of phonon angular momentum. We then demonstrate that intense THz pulses can nonlinearly excite octahedral twist modes of the inorganic sublattice in hybrid MAPbBr3 and all-inorganic CsPbBr3 lead halide perovskites (LHPs). Using THz-induced Kerr effect spectroscopy, we show that these Raman-active phonons at ~1 THz dominate the lattice contribution to the nonlinear THz polarizability at low temperatures. Since these lattice modes strongly couple to the electronic bandgap, this finding demonstrates the potential for phonon-driven ultrafast bandgap control in LHPs. Finally, we show that intense THz pulses can quench the total photoluminescence (PL) emission in the wide-bandgap semiconductor ZnTe by more than 60%. Using optical pump-THz probe techniques, we find that the THz field reduces the carrier lifetime, suggesting enhanced non-radiative recombination as the origin of the THz-induced PL quenching.
Together, these results demonstrate the potential of intense THz pulses to control structural and charge carrier dynamics in conventional and emerging semiconductors, enabling ultrafast control of the electronic bandgap, carrier lifetime, and PL emission.
Time & Location
May 28, 2025 | 10:30 AM
Hörsaal B (0.1.01)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)