Phonon driven Floquet matter

Nano Letters 18, 1535 - 1542 (2018)

Phonon driven Floquet matter

H.Hübener,U.De Giovannini, A.Rubio

A resonantly excited coherent phonon leads to a periodic oscillation of the atomic lattice in a crystal structure bringing the material into a non-equilibrium electronic configuration. Periodically oscillating quantum systems can be understood in terms of Floquet theory, which has a long tradition in the study of semi-classical light-matter interaction. Here, we show that the concepts of Floquet analysis can be applied to coherent lattice vibrations reecting the underlying coupling mechanism between electrons and coherent bosonic modes. This coupling leads to phonon- or photon-dressed quasi-particles (polarons or polaritons) imprinting specific signatures in the spectrum of the electronic structure. Such dressed electronic states can be detected by time and angular-resolved photoelectron spectroscopy (ARPES) manifesting as sidebands to the equilibrium band structure. Taking graphene as a paradigmatic material with strong electron-phonon interaction and non-trivial topology we show how the phonon-dressed states display an intricate sideband structure revealing the electron-phonon coupling at the Brillouin zone center and topological ordering of the Dirac bands. Most strikingly, we find that the non-equilibrium electronic structure created by coherent dynamical dressing is the same for photon and phonon perturbations.We demonstrate that if time-reversal symmetry is broken by the coherent lattice perturbations a topological phase transition can be induced. This work establishes that the recently demonstrated concept of light-induced non-equilibrium Floquet phases can also be applied when using coherent phonon modes for the dynamical control of material properties. The present results are generic for bosonic time-dependent perturbations, therefore we envision similar phenomena to be observed for example for plasmon, magnon or exciton driven materials.

Additional Information

Preprint - 3.9 MB
Doi 10.1021/acs.nanolett.7b05391
We are grateful for illuminating discussions with I. Gierz, S. Aeschlimann, M. A. Sentef,and Th. Brumme. We acknowledge financial support from the European Research Council(ERC-2015-AdG-694097), Grupos Consolidados (IT578-13) and the European Unions Horizon 2020 Research and Innovation program under Grant Agreements no. 676580 (NOMAD)and 646259 (MOSTOPHOS).

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