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Current amplification and relaxation in Dirac systems

Junck, Alexandra and Refael, Gil and von Oppen, Felix (2014) Current amplification and relaxation in Dirac systems. Physical Review B, 90 (24). Art. No. 245110. ISSN 1098-0121. doi:10.1103/PhysRevB.90.245110.

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Recent experiments provide evidence for photocurrent generation in Dirac systems such as topological-insulator surface states and graphene. Within the simplest picture, the magnitude of the photocurrents is governed by the competition between photoexcitation of particle-hole pairs and current relaxation by scattering. Here, we study the relaxation of photocurrents by electron-electron (e−e) collisions, which should dominate in clean systems. We compute the current relaxation rate as a function of the initial energies of the photoexcited carriers and the Fermi energy. For a positive Fermi energy, we find that collisions of a single excited electron with the Fermi sea can substantially increase the current, while for a single excited hole the current initially decreases. Together these processes partially cancel leading to a relative suppression of the relaxation of the total photocurrent carried by an electron-hole pair. We also analyze the limit of many scattering events and find that while e−e collisions initially reduce the current associated with a single hole, the current eventually reverses sign and becomes as large in magnitude as in the electron case. Thus, for photoexcited electron-hole pairs, the current ultimately relaxes to zero. We discuss schemes which may allow one to probe the nontrivial current amplification physics for individual carriers in experiment.

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Additional Information:© 2014 American Physical Society. Received 14 January 2014; revised manuscript received 1 October 2014; published 2 December 2014. We thank J. Eisenstein, Erik Henriksen, Justin Song, Feng Wang, and Andrea Young for discussions and acknowledge financial support through SPP 1666 of the Deutsche Forschungsgemeinschaft and a Helmholtz Virtual Institute “New States of Matter and Their Excitations” (Berlin), as well as DARPA, the IQIM, an NSF institute supported by the Moore Foundation, and the Humboldt Foundation (Pasadena).
Group:Institute for Quantum Information and Matter
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)SPP 1666
Helmholtz Virtual InstituteUNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Institute for Quantum Information and Matter (IQIM)UNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
Issue or Number:24
Classification Code:PACS: 73.23.−b, 72.20.Jv, 73.20.At, 78.68.+m
Record Number:CaltechAUTHORS:20140715-163241220
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47248
Deposited By: Jacquelyn O'Sullivan
Deposited On:16 Jul 2014 15:45
Last Modified:10 Nov 2021 17:37

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