Direct Observation of Collective Modes of the Charge Density Wave in the Kagome Metal CsV${}_3$Sb${}_5$

Abstract

A new group of kagome metals AV${}_3$Sb${}_5$ (A = K, Rb, Cs) exhibit a variety of intertwined unconventional electronic phases, which emerge from a puzzling charge density wave phase. Understanding of this parent charge order phase is crucial for deciphering the entire phase diagram. However, the mechanism of the charge density wave is still controversial, and its primary source of fluctuations - the collective modes - have not been experimentally observed. Here, we use ultrashort laser pulses to melt the charge order in CsV${}_3$Sb${}_5$ and record the resulting dynamics using femtosecond angle-resolved photoemission. We resolve the melting time of the charge order and directly observe its amplitude mode, imposing a fundamental limit for the fastest possible lattice rearrangement time. These observations together with ab-initio calculations provide clear evidence for a structural rather than electronic mechanism of the charge density wave. Our findings pave the way for better understanding of the unconventional phases hosted on the kagome lattice.

17 pages, 4 figures

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• Coherent phonon spectroscopy and interlayer modulation of charge density wave order in the kagome metal CsV${}_3$Sb${}_5$
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• Charge-Density-Wave-Induced Peak-Dip-Hump Structure and the Multiband Superconductivity in a Kagome Superconductor CsV${}_3$Sb${}_5$
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• Revealing the immediate formation of two-fold rotation symmetry in charge-density-wave state of Kagome superconductor CsV${}_3$Sb${}_5$ by optical polarization rotation measurement
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• Mode-selective coupling of coherent phonons to the Bi2212 electronic band structure
• Spectroscopic Evidence for a Three-Dimensional Charge Density Wave in Kagome Superconductor CsV${}_3$Sb${}_5$
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Cited by in corpus (9)

• AV${}_3$Sb${}_5$ Kagome Superconductors: Progress and Future Directions
• Time- and Angle-Resolved Photoemission Studies of Quantum Materials
• Emergent topological quantum orbits in the charge density wave phase of kagome metal CsV${}_3$Sb${}_5$
• Dynamical decoding of the competition between charge density waves in a kagome superconductor
• Unveiling van Hove singularity modulation and fluctuated charge order in kagome superconductor $\mathrm{Cs}{\mathrm{V}}_3\mathrm{S}{\mathrm{b}}_5$ via time-resolved ARPES
• Coherent Phonon Pairs and Rotational Symmetry Breaking of Charge Density Wave Order in the Kagome Superconductor CsV${}_3$Sb${}_5$
• Frustrated phonon with charge density wave in vanadium Kagome metal
• Nonequilibrium control of kagome metals
• Emergence of a hidden-order phase well below the charge density wave transition in a topological Weyl semimetal (TaSe${}_4$)${}_2$I