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TT: Fachverband Tiefe Temperaturen

TT 44: Nonequilibrium Quantum Systems I (joint session TT/DY)

TT 44.1: Vortrag

Mittwoch, 11. März 2026, 09:30–09:45, CHE/0091

Quantum geometric force in nonlinear phononics — •Sota Kitamura and Takahiro Morimoto — University of Tokyo, Tokyo, Japan

When phonons are resonantly excited by intense laser fields, nonlinear effects can dynamically alter the crystal structure. The field of controlling material properties through such processes is referred to as nonlinear phononics. In conventional theoretical frameworks of nonlinear phononics, the electron dynamics are typically assumed to be adiabatic. However, this assumption generally breaks down under strong driving, and nonadiabatic corrections become essential.

Using nonequilibrium Green function methods, we investigate the electron dynamics under resonant phonon excitation beyond the adiabatic approximation, thereby exploring nonadiabatic effects appearing in the phonon equations of motion. Our analysis reveals that quantum geometric contributions originating from the electronic Berry curvature give rise to unconventional forces on phonons. These quantum geometric corrections are then applied to the dynamical control of crystal chirality, i.e., right- or left-handedness of chiral crystals, using a minimal tight-binding model coupled to the Peierls phonon.

Keywords: Nonlinear phononics; Quantum geometry; Chiral crystal; Nonequilibrium Green function