Quantum Matter Seminar

Coherent phonons offer an ultrafast, time-domain window into driven lattice dynamics, allowing one to directly follow how vibrational motion couples to electronic degrees of freedom and to other lattice modes, and how these couplings reshape the effective phonon potential out of equilibrium. In this talk, I will use SnTe, a narrow-gap semiconducting ferroelectric, as a case study to show how ultrafast coherent-phonon spectroscopy can (i) disentangle thermal renormalization from carrier-driven contributions to apparent phonon anharmonicity, and (ii) reveal non-adiabatic ferroelectric dynamics in which electronic and ionic motion become strongly intertwined and the Born–Oppenheimer picture breaks down for the soft mode.