Condensation of collective charge ordering in Chromium

TL;DR

This study investigates how the charge density wave in chromium responds to ultrafast optical excitation, revealing persistent lattice distortions that influence the recovery of charge order, emphasizing the lattice's role in charge-ordered systems.

Contribution

It demonstrates that the charge density wave in chromium persists after excitation due to long-lived lattice displacements, affecting the dynamics of charge order recovery.

Findings

CDW amplitude reduces but is not fully disrupted after excitation

CDW period remains unchanged at elevated temperatures

CDW revives within 1 nanosecond in accordance with equilibrium temperature dependence

Abstract

Here we report on the dynamics of the structural order parameter in a chromium film using synchrotron radiation in response to photo-induced ultra-fast excitations. Following transient optical excitations the effective lattice temperature of the film rises close to the N\'{e}el temperature and the charge density wave (CDW) amplitude is reduced. Although we expect the electronic charge ordering to vanish shortly after the excitation we observe that the CDW is never completely disrupted, which is revealed by its unmodified period at elevated temperatures. We attribute the persistence of the CDW to the long-lived periodic lattice displacement in chromium. The long-term evolution shows that the CDW revives to its initial strength within 1 ns, which appears to behave in accordance with the temperature dependence in equilibrium. This study highlights the fundamental role of the lattice distortion in charge ordered systems and its impact on the re-condensation dynamics of the charge ordered state in strongly correlated materials.