Metal-insulator transitions

Masatoshi Imada, Atsushi Fujimori, Yoshinori Tokura

Research output: Contribution to journalArticle

4819 Citations (Scopus)

Abstract

Metal-insulator transitions are accompanied by huge resistivity changes, even over tens of orders of magnitude, and are widely observed in condensed-matter systems. This article presents the observations and current understanding of the metal-insulator transition with a pedagogical introduction to the subject. Especially important are the transitions driven by correlation effects associated with the electron-electron interaction. The insulating phase caused by the correlation effects is categorized as the Mott Insulator. Near the transition point the metallic state shows fluctuations and orderings in the spin, charge, and orbital degrees of freedom. The properties of these metals are frequently quite different from those of ordinary metals, as measured by transport, optical, and magnetic probes. The review first describes theoretical approaches to the unusual metallic states and to the metal-insulator transition. The Fermi-liquid theory treats the correlations that can be adiabatically connected with the noninteracting picture. Strong-coupling models that do not require Fermi-liquid behavior have also been developed. Much work has also been done on the scaling theory of the transition. A central issue for this review is the evaluation of these approaches in simple theoretical systems such as the Hubbard model and t-J models. Another key issue is strong competition among various orderings as in the interplay of spin and orbital fluctuations. Experimentally, the unusual properties of the metallic state near the insulating transition have been most extensively studied in d-electron systems. In particular, there is revived interest in transition-metal oxides, motivated by the epoch-making findings of high-temperature superconductivity in cuprates and colossal magnetoresistance in manganites. The article reviews the rich phenomena of anomalous metallicity, taking as examples Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Ru compounds. The diverse phenomena include strong spin and orbital fluctuations, mass renormalization effects, incoherence of charge dynamics, and phase transitions under control of key parameters such as band filling, bandwidth, and dimensionality. These parameters are experimentally varied by doping, pressure, chemical composition, and magnetic fields. Much of the observed behavior can be described by the current theory. Open questions and future problems are also extracted from comparison between experimental results and theoretical achievements.

Original languageEnglish
Pages (from-to)1039-1263
Number of pages225
JournalReviews of Modern Physics
Volume70
Issue number4 PART I
Publication statusPublished - 1998 Oct 1
Externally publishedYes

Fingerprint

insulators
metals
Fermi liquids
orbitals
incoherence
magnetic probes
probes
transition points
cuprates
metallicity
metal oxides
chemical composition
electron scattering
electrons
superconductivity
degrees of freedom
transition metals
time measurement
bandwidth
scaling

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Imada, M., Fujimori, A., & Tokura, Y. (1998). Metal-insulator transitions. Reviews of Modern Physics, 70(4 PART I), 1039-1263.

Metal-insulator transitions. / Imada, Masatoshi; Fujimori, Atsushi; Tokura, Yoshinori.

In: Reviews of Modern Physics, Vol. 70, No. 4 PART I, 01.10.1998, p. 1039-1263.

Research output: Contribution to journalArticle

Imada, M, Fujimori, A & Tokura, Y 1998, 'Metal-insulator transitions', Reviews of Modern Physics, vol. 70, no. 4 PART I, pp. 1039-1263.
Imada M, Fujimori A, Tokura Y. Metal-insulator transitions. Reviews of Modern Physics. 1998 Oct 1;70(4 PART I):1039-1263.
Imada, Masatoshi ; Fujimori, Atsushi ; Tokura, Yoshinori. / Metal-insulator transitions. In: Reviews of Modern Physics. 1998 ; Vol. 70, No. 4 PART I. pp. 1039-1263.
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