On metal-insulator transitions
About: This article is published in Journal of Solid State Chemistry.The article was published on 1990-09-01. It has received 842 citations till now. The article focuses on the topics: Metal–insulator transition & Mott transition.
Citations
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TL;DR: Transparent conductors (TCs) have a multitude of applications for solar energy utilization and for energy savings, especially in buildings as discussed by the authors, which leads naturally to considerations of spectral selectivity, angular selectivity, and temporal variability of TCs, as covered in three subsequent sections.
1,471 citations
TL;DR: In this article, the progress that has taken place since 1993 with regard to film deposition, characterization by physical and chemical techniques, optical properties, as well as electrochromic device assembly and performance is reviewed.
1,304 citations
TL;DR: In this paper, the combined influence of electron correlation and spin-orbit coupling (SOC), with an emphasis on emergent quantum phases and transitions in heavy transition metal compounds with 4d and 5d elements, is discussed.
Abstract: We discuss phenomena arising from the combined influence of electron correlation and spin-orbit coupling (SOC), with an emphasis on emergent quantum phases and transitions in heavy transition metal compounds with 4d and 5d elements. A common theme is the influence of spin-orbital entanglement produced by SOC, which influences the electronic and magnetic structure. In the weak-to-intermediate correlation regime, we show how nontrivial band-like topology leads to a plethora of phases related to topological insulators (TIs). We expound these ideas using the example of pyrochlore iridates, showing how many novel phases, such as the Weyl semimetal, axion insulator, topological Mott insulator, and TIs, may arise in this context. In the strong correlation regime, we argue that spin-orbital entanglement fully or partially removes orbital degeneracy, reducing or avoiding the normally ubiquitous Jahn-Teller effect. As we illustrate for the honeycomb-lattice iridates and double perovskites, this leads to enhanced qu...
1,012 citations
TL;DR: In this paper, the authors discuss the role of materials synthesis in influencing functional properties and discuss future research directions that may be worth consideration, concluding with a brief discussion on future directions that are worth consideration.
Abstract: Although phase transitions have long been a centerpiece of condensed matter materials science studies, a number of recent efforts focus on potentially exploiting the resulting functional property changes in novel electronics and photonics as well as understanding emergent phenomena. This is quite timely, given a grand challenge in twenty-first-century physical sciences is related to enabling continued advances in information processing and storage beyond conventional CMOS scaling. In this brief review, we discuss synthesis of strongly correlated oxides, mechanisms of metal-insulator transitions, and exploratory electron devices that are being studied. Particular emphasis is placed on vanadium dioxide, which undergoes a sharp metal-insulator transition near room temperature at ultrafast timescales. The article begins with an introduction to metal-insulator transition in oxides, followed by a brief discussion on the mechanisms leading to the phase transition. The role of materials synthesis in influencing functional properties is discussed briefly. Recent efforts on realizing novel devices such as field effect switches, optical detectors, nonlinear circuit components, and solid-state sensors are reviewed. The article concludes with a brief discussion on future research directions that may be worth consideration.
859 citations
TL;DR: In this paper, the linear and nonlinear optical responses of Langmuir monolayers of organically functionalized silver quantum dots were measured as a continuous function of interparticle separation under near-ambient conditions.
Abstract: The linear and nonlinear (χ(2)) optical responses of Langmuir monolayers of organically functionalized silver quantum dots were measured as a continuous function of interparticle separation under near-ambient conditions. As the distance between metal surfaces was decreased from 12 to ∼5 angstroms, both quantum and classical effects were observed in the optical signals. When the separation was less than 5 angstroms, the optical second-harmonic generation (SHG) response exhibited a sharp discontinuity, and the linear reflectance and absorbance began to resemble those of a thin metallic film, indicating that an insulator-to-metal transition occurred. This transition was reversible.
805 citations
References
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TL;DR: In this paper, it was shown that the conductance of disordered electronic systems depends on their length scale in a universal manner, and asymptotic forms for the scaling function were obtained for both two-dimensional and three-dimensional systems.
Abstract: Arguments are presented that the $T=0$ conductance $G$ of a disordered electronic system depends on its length scale $L$ in a universal manner. Asymptotic forms are obtained for the scaling function $\ensuremath{\beta}(G)=\frac{d\mathrm{ln}G}{d\mathrm{ln}L}$, valid for both $G\ensuremath{\ll}{G}_{c}\ensuremath{\simeq}\frac{{e}^{2}}{\ensuremath{\hbar}}$ and $G\ensuremath{\gg}{G}_{c}$. In three dimensions, ${G}_{c}$ is an unstable fixed point. In two dimensions, there is no true metallic behavior; the conductance crosses over smoothly from logarithmic or slower to exponential decrease with $L$.
4,466 citations
Book•
01 Jan 1974
TL;DR: In this article, a discussion is given of some aspects of the metal insulator transition and the status of the "minimum metallic conductivity" is discussed, and the concept is valid for liquids and in some, but not all, solid systems.
Abstract: A discussion is given of some aspects of the metal insulator transition. Particular attention is paid to the status of the “minimum metallic conductivity”. The concept is valid for liquids, and in some, but not all, solid systems.
2,109 citations
TL;DR: In this paper, the authors review the thermodynamic and electromagnetic properties of such systems in several limiting scenarios: (i) systems with on-site pairing which can be described by the extended negative-$U$ Hubbard model, at which it reduces to a system of tightly bound electron pairs (bipolarons) on a lattice, and the changeover from weak-attraction BCS-like superconductivity to the superfluidity of charged hard core bosons is examined.
Abstract: In narrow-band systems electrons can interact with each other via a short-range nonretarded attractive potential. The origin of such an effective local attraction can be polaronic or it can be due to a coupling between electrons and excitons or plasmons. It can also result from purely chemical (electronic) mechanisms, especially in compounds with elements favoring disproportionation of valent states. These mechanisms are discussed and an exhaustive list of materials in which such local electron pairing occurs is given. The authors review the thermodynamic and electromagnetic properties of such systems in several limiting scenarios: (i) Systems with on-site pairing which can be described by the extended negative-$U$ Hubbard model. The strong-attraction limit of this model, at which it reduces to a system of tightly bound electron pairs (bipolarons) on a lattice, is extensively discussed. These electron pairs behaving as hard-core charged bosons can exhibit a superconducting state analogous to that of superfluid $^{4}\mathrm{He}$ II. The change-over from weak-attraction BCS-like superconductivity to the superfluidity of charged hard-core bosons is examined. (ii) Systems with intersite pairing described by an extended Hubbard model with $Ug0$ and nearest-neighbor attraction and/or nearest-neighbor spin exchange as well as correlated hopping. (iii) A mixture of local pairs and itinerant electrons interacting via a charge-exchange mechanism giving rise to a mutually induced superconductivity in both subsystems. The authors discuss to what extent the picture of local pairing, and in particular superfluidity of hard-core charged bosons on a lattice, can be an explanation for the superconducting and normal-state properties of the high-${T}_{c}$ oxides: doped BaBi${\mathrm{O}}_{3}$ and the cuprates.
1,276 citations
TL;DR: In this paper, the authors evaluated the minimum metallic conductivity in disordered materials, proposed by the author in previous papers, in the light of the revised criterion for Anderson localization given by Edwards and Thouless (1972).
Abstract: The minimum metallic conductivity in disordered materials, proposed by the author in previous papers, is evaluated in the light of the revised criterion for Anderson localization given by Edwards and Thouless (1972). The experimental evidence resulting from the recent work of Allen and Adkins (1972) is reviewed, as is also the discussion by Cohen (1971) and Eggarter (1972) based on percolation theory. This and other evidence suggests strongly that a minimum metallic conductivity does exist having approximately the calculated value.
346 citations
TL;DR: In this paper, the ground-state energies of electron-hole metals were calculated using Hubbard's approximate treatment of the electron gas for the following cases: (a) germanium, (b) GHE with a large (111) strain, (c) silicon, and (d) GaAs.
Abstract: In this paper the energetics of the formation of electron-hole metallic liquids in semiconductors is examined. The ground-state energies of electron-hole metals are calculated using Hubbard's approximate treatment of the electron gas for the following cases: (a) germanium, (b) germanium with a large (111) strain, (c) silicon, and (d) GaAs. The simple case of a single isotropic maximum for the valence band and a single minimum for the conduction band is also treated. It is shown that for both Si and Ge, the binding energy of the metallic state relative to free excitons is 5.7 and 1.7 meV, respectively. These values and the values of the equilibrium density are in good agreement with experiment. In the isotropic model the metallic state is not bound while for GaAs and strained Ge the metallic-state energy per electron is essentially equal to that for a gas of free excitons. The low-density limit of the isotropic band model is examined and the ground state for this system is predicted to be a dilute gas of molecules. It is argued that the forces between molecules are repulsive and will cause this state to break up at relatively low densities. If the density is increased, the system will undergo a first-order transition to the metallic state. The relevance of these calculations to the metal-insulator transition problem is discussed. It is pointed out that the fact that anisotropic and many-valleyed bands favor the metallic state means that the metal-insulator transition must ultimately be first order.
298 citations