Relativistic nature of a magnetoelectric modulus of Cr2O3 crystals: A four-dimensional pseudoscalar and its measurement

Friedrich W. Hehl, Yuri N. Obukhov, Jean-Pierre Rivera, and Hans Schmid
Phys. Rev. A 77, 022106 – Published 14 February 2008

Abstract

The magnetoelectric effect of chromium sesquioxide Cr2O3 has been determined experimentally as a function of temperature. One measures the electric field-induced magnetization on Cr2O3 crystals or the magnetic field-induced polarization. From the magnetoelectric moduli of Cr2O3 we extract a four-dimensional relativistic invariant pseudoscalar α̃. It is temperature dependent and of the order of 104Z0, with Z0 as vacuum impedance. We show that the new pseudoscalar is odd under parity transformation and odd under time inversion. Moreover, α̃ is for Cr2O3 what Tellegen’s gyrator is for two port theory, the axion field for axion electrodynamics, and the PEMC (perfect electromagnetic conductor) for electrical engineering.

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  • Received 30 July 2007

DOI:https://doi.org/10.1103/PhysRevA.77.022106

©2008 American Physical Society

Authors & Affiliations

Friedrich W. Hehl*

  • Institute for Theoretical Physics, University of Cologne, 50923 Köln, Germany and Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, Missouri 65211, USA

Yuri N. Obukhov

  • Institute for Theoretical Physics, University of Cologne, 50923 Köln, Germany and Department of Theoretical Physics, Moscow State University, 117234 Moscow, Russia

Jean-Pierre Rivera and Hans Schmid§

  • Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Sciences II, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland

  • *hehl@thp.uni-koeln.de
  • yo@thp.uni-koeln.de
  • Jean-Pierre.Rivera@chiam.unige.ch
  • §Hans.Schmid@chiam.unige.ch

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Vol. 77, Iss. 2 — February 2008

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