Observation of electronic structure replicas in photoemission spectra of graphite upon adsorption of tin phthalocyanine.

Cone-type bands near the center of the surface Brillouin zone were observed in low-energy angle-resolved photoemission spectra of tin phthalocyanine adsorbed on graphite. Simulations in comparison with the experimental data show that the spectral features represent replicas of the electronic structure of graphite nearK‾resulting from high-order momentum transfer processes up to the fourth order owing to the interaction of substrate electrons with the long-range structural order of the adsorbate overlayer. The analysis of time-resolved photoemission data from one of the replicas yields a quantitative and very good agreement with previous studies on the excited carrier dynamics in the Dirac cones of graphite and graphene.

Mode-resolved reciprocal space mapping of electron-phonon interaction in the Weyl semimetal candidate Td-WTe.

The excitation of coherent phonons provides unique capabilities to control fundamental properties of quantum materials on ultrafast time scales. Recently, it was predicted that a topologically protected Weyl semimetal phase in the transition metal dichalcogenide Td-WTe can be controlled and, ultimately, be destroyed upon the coherent excitation of an interlayer shear mode. By monitoring electronic structure changes with femtosecond resolution, we provide here direct experimental evidence that the shear mode acts on the electronic states near the phase-defining Weyl points.

A combined laser-based angle-resolved photoemission spectroscopy and two-photon photoemission spectroscopy study of-WTe.

Laser-based angle-resolved photoemission spectroscopy and two-photon photoemission spectroscopy are employed to study the valence electronic structure of the Weyl semimetal candidate-WTealong two high symmetry directions and for binding energies between ≈ -1 eV and 5 eV. The experimental data show a good agreement with band structure calculations. Polarization dependent measurements provide further information on initial and intermediate state symmetry properties with respect to the mirror plane of thestructure of WTe.