Observation of the charge density wave collective mode in the infrared optical response of VSe${}_2$

Abstract

We present a detailed study of the bulk electronic structure of high quality VSe${}_2$ single crystals using optical spectroscopy. Upon entering the charge density wave phase below the critical temperature of 112 K, the optical conductivity of VSe${}_2$ undergoes a significant rearrangement. A Drude response present above the critical temperature is suppressed while a new interband transition appears around 0.07\,eV. From our analysis, we estimate that part of the spectral weight of the Drude response is transferred to a collective mode of the CDW phase. The remaining normal state charge dynamics appears to become strongly damped by interactions with the lattice as evidenced by a mass enhancement factor m${}^{\ast }$/m$\approx$3. In addition to the changes taking place in the electronic structure, we observe the emergence of infrared active phonons below the critical temperature associated with the 4a x 4a lattice reconstruction.

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Cited by in corpus (2)

• Spectrally resolving the phase and amplitude of coherent phonons in the charge density wave state of 1$T$-TaSe${}_2$
• Anomalous amplitude mode dynamics below the expected charge-density-wave transition in 1$T$-VSe${}_2$