Speaker
Description
Pseudospin, a degree of freedom in a two-level quantum system of two sublattices, is a basic quantum number posing the fundamental symmetry prone to the electronic nature of graphene. We propose an extended Hamiltonian to involve the SU(2) rotation of pseudospin for the electron-phonon scattering, which has a significant merit over the conventional second-quantized polar coupling. A phonon satellite accompanied by an electron linearly pumped to the upper Dirac cone corresponds to a rotated pseudospin within a scheme of the time-resolved photoemission spectroscopy (TRPES), which is found to carry nonzero angular momenta and induce nonvanishing Berry curvatures through the dichroic mode of TRPES. A phonon bringing the pseudospin rotation is identified to be an elliptically polarized one, which compensates angular momenta delivered to the pseudospin. This is an indication of the chiral phonon excitation without the circularly polarized pulse pumping. Our findings suggest that a controlled generation of phonon build up a new roadmap for engineering the Berry curvature and topology in the Dirac semiconductors.
