Optically Induced Avoided Crossing in Graphene

RWTH Publications (RWTH Aachen)

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 non-equilibrium 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 E1u and E2g symmetry, which are virtually uncoupled at equilibrium. New vibronic states result from anharmonic driving of the E1u mode to large amplitdues, boosting its coupling to the E2g 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 non-equilibrium 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 , Germany

2. Benjamin Grimm‐Lebsanft

   Universität Hamburg

   Affiliation as printed

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

3. Florian Biebl

   Universität Hamburg

   Affiliation as printed

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

4. Tomke Eva Glier

   Universität Hamburg

   Affiliation as printed

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

5. Lea Westphal

   Universität Hamburg

   Affiliation as printed

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

6. Janika Reichstetter

   Max Planck Institute for Solid State Research

   Affiliation as printed

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

7. Dirk Manske

   Max Planck Institute for Solid State Research

   Affiliation as printed

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

8. M. Fechner

   Max Planck Institute for the Structure and Dynamics of Matter

   Affiliation as printed

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

9. A. Cavalleri

   Max Planck Institute for the Structure and Dynamics of Matter

   Affiliation as printed

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

10. Sonja Herres‐Pawlis Aachen Institute of Inorganic Chemistry

    RWTH Aachen University

    Affiliation as printed

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

11. Michael Rübhausen