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Axion Response in Gapless Systems

Bergman, Doron L. (2011) Axion Response in Gapless Systems. Physical Review Letters, 107 (17). p. 176801. ISSN 0031-9007.

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The strong topological insulator in 3D is expected to realize a quantized magnetoelectric response, the so-called axion response. However, many of the materials predicted to be topological insulators have turned out to be metallic, with bulk Fermi surfaces. Following the result of Bergman and Refael [Phys. Rev. B 82 195417 (2010)] that the surface states of the topological insulator persist even when the band structure gap is closed, we explore the fate of the magnetoelectric response in such systems. We find that a nonquantized magnetoelectric coupling remains once a bulk Fermi surface opens. More generally, we find higher-dimensional analogs of the intrinsic anomalous Hall effect for all Chern forms—quantized transport coefficients in the gapped case become nonquantized when the gap is closed. In particular, the nonquantized magnetoelectric response in 3D descends from the intrinsic anomalous Hall effect analog in 4D.

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Additional Information:© 2011 American Physical Society. Received 22 February 2011; published 17 October 2011. D. L. B. was supported by the Sherman Fairchild foundation and acknowledges discussion with G. Refael and M. P. A. Fisher. Also, I thank G. E. Volovik, for pointing me to a discussion of topological effects in gapless systems.
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Sherman Fairchild FoundationUNSPECIFIED
Issue or Number:17
Classification Code:PACS: 73.20.At, 72.20.-i
Record Number:CaltechAUTHORS:20111121-101239195
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27886
Deposited By: Jason Perez
Deposited On:21 Nov 2011 19:36
Last Modified:03 Oct 2019 03:27

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