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Phys. Rev. B 74, 024408 (2006) [13 pages]

Orbital magnetization in crystalline solids: Multi-band insulators, Chern insulators, and metals

Davide Ceresoli,1 T. Thonhauser,2 David Vanderbilt,2 and R. Resta3
1Scuola Internazionale Superiore di Studi Avanzati (SISSA/ISAS) and DEMOCRITOS, via Beirut 2-4, 34014 Trieste, Italy
2Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
3Dipartimento di Fisica Teorica, Università di Trieste and DEMOCRITOS, strada Costiera 11, 34014 Trieste, Italy

Received 7 December 2005; revised 6 March 2006; published 12 July 2006

We derive a multi-band formulation of the orbital magnetization in a normal periodic insulator (i.e., one in which the Chern invariant, or in two dimensions (2D) the Chern number, vanishes). Following the approach used recently to develop the single-band formalism [Thonhauser, Ceresoli, Vanderbilt, and Resta, Phys. Rev. Lett. 95, 137205 (2005)], we work in the Wannier representation and find that the magnetization is comprised of two contributions, an obvious one associated with the internal circulation of bulklike Wannier functions in the interior and an unexpected one arising from net currents carried by Wannier functions near the surface. Unlike the single-band case, where each of these contributions is separately gauge invariant, in the multi-band formulation only the sum of both terms is gauge invariant. Our final expression for the orbital magnetization can be rewritten as a bulk property in terms of Bloch functions, making it simple to implement in modern code packages. The reciprocal-space expression is evaluated for 2D model systems and the results are verified by comparing to the magnetization computed for finite samples cut from the bulk. Finally, while our formal proof is limited to normal insulators, we also present a heuristic extension to Chern insulators (having nonzero Chern invariant) and to metals. The validity of this extension is again tested by comparing to the magnetization of finite samples cut from the bulk for 2D model systems. We find excellent agreement, thus providing strong empirical evidence in favor of the validity of the heuristic formula.

©2006 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevB.74.024408
DOI: 10.1103/PhysRevB.74.024408
PACS: 75.10.Lp; 73.20.At; 73.43.-f
  • 75.10.Lp
    Band and itinerant models (magnetism)
  • 73.20.At
    Surface states, band structure, electron density of states
  • 73.43.-f
    Quantum Hall effects
  • YEAR: 2006
KEYWORDS: magnetisation, Wannier functions, band model of magnetism

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