Unveiling van Hove singularity modulation and fluctuated charge order in kagome superconductor $\rm{CsV_3Sb_5}$ via time-resolved ARPES

TL;DR

This study uses time-resolved ARPES to reveal how laser excitation modulates van Hove singularities and induces coherent phonons in CsV3Sb5, providing insights into fluctuated charge order and its relation to superconductivity.

Contribution

It uncovers the dynamic behavior of van Hove singularities and coherent phonons in CsV3Sb5, highlighting persistent phonon modes above the charge density wave transition temperature.

Findings

Van Hove singularities shift towards the Fermi level upon laser excitation.

A 1.3 THz coherent phonon mode is strongly coupled with electronic bands.

Persistent phonon excitation above T_CDW suggests fluctuated charge density wave presence.

Abstract

Kagome superconductor CsV3Sb5, which exhibits intertwined unconventional charge density wave (CDW) and superconductivity, has garnered significant attention recently. Despite extensive static studies, the nature of these exotic electronic orders remains elusive. In this study, we investigate the non-equilibrium electronic structure of CsV3Sb5 via time- and angle-resolved photoemission spectroscopy. Our results reveal that upon laser excitation, the van Hove singularities immediately shift towards the Fermi level and subsequently oscillate in sync with a 1.3 THz coherent phonon mode. By analyzing the coherent intensity oscillations in the energy-momentum (E-k) map, we find that this coherent phonon is strongly coupled with electronic bands from both Sb and V orbitals. While typically observable only in the CDW state, remarkably, we find that the 1.3-THz coherent phonon mode can be persistently excited at temperatures above T_CDW, suggesting the potential existence of fluctuated CDW in CsV3Sb5. These findings enhance our understanding of the unconventional CDW control of kagome superconductivity.