Abstract-Ultrafast terahertz response of multilayer graphene in the nonperturbative regime

P. Bowlan, E. Martinez-Moreno, K. Reimann, T. Elsaesser, and M. Woerner
Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany

 Published 27 January 2014; received 18 June 2013

The nonlinear dynamics of electrons in multilayer epitaxial graphene is investigated by time-resolved terahertz (THz) spectroscopy in a regime where the interaction of electrons with the external field dominates over scattering processes. The predominantly coherent electron response to the THz field involves both intra- and interband currents, leading to coherently driven interband transitions of carriers and to the generation of higher harmonics of the THz carrier frequency. The overall behavior of the graphene layers is always absorptive, even after generation of an initial electron-hole distribution by femtosecond midinfrared excitation. The results are in agreement with theoretical calculations of the nonperturbative THz response.

©2014 American Physical Society

URL:

http://link.aps.org/doi/10.1103/PhysRevB.89.041408

DOI:

10.1103/PhysRevB.89.041408

PACS:

72.80.Vp, 72.20.Ht, 73.22.Pr, 78.47.J-

Abstract-Ultrafast terahertz response of multilayer graphene in the nonperturbative regime

P. Bowlan, E. Martinez-Moreno, K. Reimann, T. Elsaesser, and M. Woerner
http://prb.aps.org/accepted/ed078Y8aSf212448242681137542a700e758b25c0
The nonlinear dynamics of electrons in multi-layer epitaxial graphene is investigated by time-resolved terahertz (THz) spectroscopy in a regime where the interaction of electrons with the external field dominates over scattering processes. The predominantly coherent electron response to the THz field involves both intra- and interband currents, leading to coherently driven interband transitions of carriers and to the generation of higher harmonics of the THz carrier frequency. The overall behavior of the graphene layers is always absorptive, even after generation of an initial electron-hole distribution by femtosecond mid-infrared excitation. The results are in agreement with theoretical calculations of the nonperturbative THz response.

High-field terahertz response of graphene

M J Paul¹, Y C Chang², Z J Thompson¹, A Stickel¹, J Wardini¹, H Choi³, E D Minot¹, T B Norris^2,4 and Yun-Shik Lee¹

tnorris@umich.edu                            
¹ Department of Physics, Oregon State University, Corvallis, OR 97331, USA
² Center for Ultrafast Optical Science and Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA
³ School of Electrical and Electronic Engineering, Yonsei University, Seoul, Republic of Kore
a

http://m.iopscience.iop.org/1367-2630/15/8/085019
We investigate the response of multi-layer epitaxial graphene and chemical vapor deposition (CVD)-grown single-layer graphene to strong terahertz (THz) fields. Contrary to theoretical predictions of strong nonlinear response, the transmitted fields exhibit no harmonic generation, indicating that the nonlinear response is limited by fast electron thermalization due to carrier–carrier scattering. The fast electron heating gives rise to large THz transmission enhancement (> 15%) in single-layer CVD graphene at high THz fields (E_THz > 10 kV cm⁻¹). The nonlinear effects exhibit non-Drude behavior in the THz conductivity, where THz fields induce extreme non-equilibrium electron distributions