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Crystals 2012, 2(2), 266-283; doi:10.3390/cryst2020266
Review

Theory of Dirac Electrons in Organic Conductors

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Received: 26 March 2012; in revised form: 10 April 2012 / Accepted: 10 April 2012 / Published: 20 April 2012
(This article belongs to the Special Issue Molecular Conductors)
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Abstract: The dynamical property of electrons with the tilted Dirac cone was examined using the tilted Weyl equation. The polarization function exhibits cusps and nonmonotonic structures by varying both the frequency and the momentum. A pair of tilted Dirac cones exhibits a new plasmon for the intermediate magnitude of momentum owing to the combined effects of two tilted cones. Dirac electrons with the zero-gap state (ZGS) in organic conductor α-(BEDT-TTF)2I3 are examined by calculating the Berry curvature, which displays the peak structure for a pair of Dirac particles between the conduction band and the valence band. The ZGS is theoretically predicted for α-(BEDT-TTF)2NH4Hg(SCN)4 under uniaxial pressure. Examining the band structure of the stripe charge ordered state of α-(BEDT-TTF)2I3 under pressure, we have found a topological transition from a conventional insulator to a new phase of a pair of Dirac electrons with a finite mass. Further, investigating the zero-energy (N = 0) Landau level under a strong magnetic field, we propose ferromagnetism breaking the SU(2) valley-pseudo-spin symmetry, and the phase fluctuations of the order parameters leading to Kosterlitz-Thouless transition at lower temperatures.
Keywords: zero-gap state; α-(BEDT-TTF)2I3; polarization function; plasma frequency; tilted Dirac cone; Berry curvature; tilted Weyl equation; α-(BEDT-TTF)2 NH4Hg(SCN)4 ; topological transition; massive Dirac particle; quantum Hall ferromagnet; Kosterlitz-Thouless transition; organic conductor zero-gap state; α-(BEDT-TTF)2I3; polarization function; plasma frequency; tilted Dirac cone; Berry curvature; tilted Weyl equation; α-(BEDT-TTF)2 NH4Hg(SCN)4; topological transition; massive Dirac particle; quantum Hall ferromagnet; Kosterlitz-Thouless transition; organic conductor
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Suzumura, Y.; Kobayashi, A. Theory of Dirac Electrons in Organic Conductors. Crystals 2012, 2, 266-283.

AMA Style

Suzumura Y, Kobayashi A. Theory of Dirac Electrons in Organic Conductors. Crystals. 2012; 2(2):266-283.

Chicago/Turabian Style

Suzumura, Yoshikazu; Kobayashi, Akito. 2012. "Theory of Dirac Electrons in Organic Conductors." Crystals 2, no. 2: 266-283.


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