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Frenzel AJ, Lui CH, Shin YC, et al. Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene. Phys Rev Lett. 2014;113(5):056602doi: 10.1103/PhysRevLett.113.056602.
Frenzel, A. J., Lui, C. H., Shin, Y. C., Kong, J., & Gedik, N. (2014). Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene. Physical review letters, 113(5), 056602. https://doi.org/10.1103/PhysRevLett.113.056602
Frenzel, A J, et al. "Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene." Physical review letters vol. 113,5 (2014): 056602. doi: https://doi.org/10.1103/PhysRevLett.113.056602
Frenzel AJ, Lui CH, Shin YC, Kong J, Gedik N. Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene. Phys Rev Lett. 2014 Aug 01;113(5):056602. doi: 10.1103/PhysRevLett.113.056602. Epub 2014 Jul 31. PMID: 25126929.
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Phys Rev Lett. 2014 Aug 01;113(5):056602. doi: 10.1103/PhysRevLett.113.056602. Epub 2014 Jul 31.

Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene.

Physical review letters

A J Frenzel, C H Lui, Y C Shin, J Kong, N Gedik

Affiliations

  1. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
  2. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
  3. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
  4. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

PMID: 25126929 DOI: 10.1103/PhysRevLett.113.056602

Abstract

We investigate the transient photoconductivity of graphene at various gate-tuned carrier densities by optical-pump terahertz-probe spectroscopy. We demonstrate that graphene exhibits semiconducting positive photoconductivity near zero carrier density, which crosses over to metallic negative photoconductivity at high carrier density. These observations can be accounted for by the interplay between photoinduced changes of both the Drude weight and carrier scattering rate. Our findings provide a complete picture to explain the opposite photoconductivity behavior reported in (undoped) graphene grown epitaxially and (doped) graphene grown by chemical vapor deposition. Notably, we observe nonmonotonic fluence dependence of the photoconductivity at low carrier density. This behavior reveals the nonmonotonic temperature dependence of the Drude weight in graphene, a unique property of two-dimensional massless Dirac fermions.

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