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Résumé |
In my talk I will review recent progress in the use of Raman scattering as a probe of electronic excitations in
two-dimensional crystals. In the first part of my talk I will discuss experiments which aim at directly observing
electronic excitations in graphene-based devices [1]. I will show in particular that symmetry-resolved Raman
experiments can selectively probe chiral excitations, offering promising venues for this technique as a probe
of non-trivial bulk and surface electron states. In the second part of my talk I will present recent Raman
results on 2D metallic transition metal dichalcogenides (NbSe2 and TaSe2) in their bulk and few-layer form. I
will discuss fingerprints of charge density wave order (CDW) and superconductivity (SC) and I will show that
the coupling between CDW and SC orders enables a Raman coupling to the amplitude mode of the
superconducting order parameter, a condensed matter analog of the Higgs mode [2]. If time allows I will also
present recent THz Kerr and third-harmonic generation experiments which aim at probing the Higgs mode in
other superconductors [3].
[1] E. Riccardi et al. Phys. Rev. Lett. 116, 066805 (2016), E. Riccardi et al. Phys. Rev. Mat. 3, 014002 (2019)
[2] R. Grasset et al. Phys. Rev. B 97, 094502 (2018), R. Grasset et al. Phys. Rev. Lett. 122, 127001 (2019)
[3] K. Katsumi et al. Phys. Rev. Lett. 120, 117001 (2018), H. Chu et al. arXiv : :1901.06675 (2019)
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