Optically induced avoided crossing in graphene

Physical review. B./Physical review. B, vol. 108

Abstract

Degenerate states in condensed matter are frequently the cause of unwanted fluctuations, which prevent the formation of ordered phases and reduce their functionalities. Removing these degeneracies has been a common theme in materials design, pursued, for example, by strain engineering at interfaces. Here we explore a nonequilibrium approach to lift degeneracies in solids. We show that coherent driving of the crystal lattice in bi- and multilayer graphene boosts the coupling between two doubly degenerate modes of ${E}_{1u}$ and ${E}_{2g}$ symmetry, which are virtually uncoupled at equilibrium. New vibronic states result from anharmonic driving of the ${E}_{1u}$ mode to large amplitudes, boosting its coupling to the ${E}_{2g}$ mode. The vibrational structure of the driven state is probed with time-resolved Raman scattering, which reveals laser-field-dependent mode splitting and enhanced lifetimes. We expect this phenomenon to be generally observable in many materials systems, affecting the nonequilibrium emergent phases in matter.

Authors 11

1. Sören Buchenau

   Universität Hamburg

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

2. Benjamin Grimm‐Lebsanft

   Universität Hamburg

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

3. Florian Biebl

   Universität Hamburg

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

4. Tomke Eva Glier

   Universität Hamburg

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

5. Lea Westphal

   Universität Hamburg

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

6. Janika Reichstetter

   Universität Hamburg · Max Planck Institute for Solid State Research

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

   Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany

7. Dirk Manske

   Universität Hamburg · Max Planck Institute for Solid State Research

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

   Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany

8. M. Fechner

   Universität Hamburg · Max Planck Institute for the Structure and Dynamics of Matter

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

   Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany

9. A. Cavalleri

   Universität Hamburg · Max Planck Institute for the Structure and Dynamics of Matter

   Affiliation as printed

   Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

   Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany

10. Sonja Herres‐Pawlis Aachen Institute of Inorganic Chemistry

    Universität Hamburg · RWTH Aachen University

    Affiliation as printed

    Institute of Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany

    Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

11. Michael Rübhausen

    Universität Hamburg

    Affiliation as printed

    Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany