Phase-channel dynamics reveal the role of impurities and screening in a quasi-one-dimensional charge-density wave system

TL;DR

This study uses ultrafast terahertz spectroscopy to explore phase excitations in a quasi-one-dimensional charge density wave system, revealing how impurities and screening influence the dynamics and electron-phonon interactions.

Contribution

It extends the time-dependent Ginzburg-Landau theory to include impurity effects and explains the photoinduced blue-shifts through electron-phonon coupling reduction.

Findings

Impurities significantly affect phase-phonon dynamics.

Photoinduced blue-shifts result from reduced electron-phonon coupling.

Temperature dependence aligns with generalized theoretical model.

Abstract

We investigate the low-energy phase excitations of the quasi-one-dimensional charge density wave (CDW) in $\mathrm{K}_{0.3}\mathrm{Mo}\mathrm{O}_3$, by direct probing of infrared-active CDW-lattice modes (phase-phonons) with ultrafast terahertz spectroscopy. Both the nonequilibrium response and temperature dependence of the bands are reconciled by generalizing the time-dependent Ginzburg-Landau theory, beyond that previously applied to the amplitude-phonons, to include impurity effects, while the photoinduced blue-shifts are attributed to a reduction of the electron-phonon coupling induced by a long-lived free-carrier population.