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McWhan, D. B.; Remeika, J. P.

doi:10.1103/physrevb.2.3734

Cited by 489 publications

(291 citation statements)

References 51 publications

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“…For such systems band theory typically predicts metallic behavior. The most famous example is V 2 O 3 doped with Cr [63][64][65]. In particular, below T = 380 K the metal-insulator transition in paramagnetic (V 0.96 Cr 0.04 ) 2 O 3 is of first order [64], with discontinuities in the lattice parameters and in the conductivity.…”

Section: The Mott-hubbard Metal-insulator Transitionmentioning

confidence: 99%

Dynamical Mean-Field Theory

Vollhardt

Byczuk

Kollar

2011

Springer Series in Solid-State Sciences

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Abstract. The dynamical mean-field theory (DMFT) is a widely applicable approximation scheme for the investigation of correlated quantum many-particle systems on a lattice, e.g., electrons in solids and cold atoms in optical lattices. In particular, the combination of the DMFT with conventional methods for the calculation of electronic band structures has led to a powerful numerical approach which allows one to explore the properties of correlated materials. In this introductory article we discuss the foundations of the DMFT, derive the underlying self-consistency equations, and present several applications which have provided important insights into the properties of correlated matter. Motivation Electronic CorrelationsAlready in 1937, at the outset of modern solid state physics, de Boer and Verwey [1] drew attention to the surprising properties of materials with incompletely filled 3d-bands. This observation prompted Mott and Peierls [2] to discuss the interaction between the electrons. Ever since transition metal oxides (TMOs) were investigated intensively [3]. It is now well-known that in many materials with partially filled electron shells, such as the 3d transition metals V and Ni and their oxides, or 4f rare-earth metals such as Ce, electrons occupy narrow orbitals. The spatial confinement enhances the effect of the Coulomb interaction between the electrons, making them "strongly correlated". Correlation effects can lead to profound quantitative and qualitative changes of the physical properties of electronic systems as compared to non-interacting particles. In particular, they often respond very strongly to changes in external parameters. This is expressed by large renormalizations of the response functions of the system, e.g., of the spin susceptibility and the charge compressibility. In particular, the interplay between the spin, charge and orbital degrees of freedom of the correlated d and f electrons and with the lattice degrees of freedom leads to an amazing multitude of ordering phenomena and other fascinating properties, including high temperature superconductivity, colossal magnetoresistance and Mott metal-insulator transitions [3].arXiv:1109.4833v1 [cond-mat.str-el]

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Section: The Mott-hubbard Metal-insulator Transitionmentioning

confidence: 99%

Dynamical Mean-Field Theory

Vollhardt

Byczuk

Kollar

2011

Springer Series in Solid-State Sciences

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“…In this case the Hilbert space is made up of 495 atomic states with up to four electrons per site and the eigen-problem is rather complicated. However, due to the SU (2) …”

Section: A the Approximate Solution Using H Effmentioning

confidence: 99%

“…• H (2) 0j represents the repulsion between electrons with the same spin on different orbitals, given by the Coulomb minus the exchange energy;…”

Section: The Modelmentioning

confidence: 99%

“…[1][2][3][4][5] As is well known, this compound is considered to be the prototype of the Mott-Hubbard systems, showing metal-insulator transitions from a paramagnetic metallic (PM) phase to an antiferromagnetic insulating (AFI) phase at low temperatures (≈ 150K) and from a PM phase to a paramagnetic insulating (PI) phase at higher temperatures (≈ 500K), due to the interplay between band formation and electron Coulomb correlation. 2 Actually it is the only known example among transition-metal oxides to show a PM to PI transition. 6 In the paramagnetic phases the crystal has the corundum structure, in which the V ions are arranged in V-V pairs along the c-hexagonal axis and form a honeycomb lattice in the basal ab plane.…”

Section: Introductionmentioning

confidence: 99%

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Spin-1 effective Hamiltonian with three degenerate orbitals: An application to the case of V2O3

2002

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Motivated by recent neutron and x-ray observations in V2O3, we derive the effective Hamiltonian in the strong coupling limit of an Hubbard model with three degenerate t2g states containing two electrons coupled to spin S = 1, and use it to re-examine the low-temperature ground-state properties of this compound. An axial trigonal distortion of the cubic states is also taken into account. Since there are no assumptions about the symmetry properties of the hopping integrals involved, the resulting spin-orbital Hamiltonian can be generally applied to any crystallographic configuration of the transition metal ion giving rise to degenerate t2g orbitals.Specializing to the case of V2O3 we consider the low temperature antiferromagnetic insulating phase. We find two variational regimes, depending on the relative size of the correlation energy of the vertical pairs and the in-plane interaction energy. The former favors the formation of stable molecules throughout the crystal, while the latter tends to break this correlated state. Using the appropriate variational wave functions we determine in both cases the minimizing orbital solutions for various spin configurations, compare their energies and draw the corresponding phase diagrams in the space of the relevant parameters of the problem. We find that none of the symmetry-breaking stable phases with the real spin structure presents an orbital ordering compatible with the magnetic space group indicated by very recent observations of non-reciprocal x-ray gyrotropy in V2O3. We do however find a compatible solution with very small excitation energy in two distinct regions of the phase space, which might turn into the true ground state of V2O3 due to the favorable coupling with the lattice. We illustrate merits and drawbacks of the various solutions and discuss them in relation to the present experimental evidence.

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“…Since Mott's landmark work 3,4 it has been known that in crystalline solids strong electron-electron interactions can cause an insulator-metal transition. One example is crystalline Cr-doped vanadium oxide, (V 1-x Cr x ) 2 O 3 , which shows a Mott transition from a paramagnetic Mott insulator to a strongly correlated metal upon an increase in pressure, a lowering of temperature, or a decrease in dopant level 5,6 . In non-crystalline solids structural disorder can also lead to an insulator-metal transition on account of Anderson localization 7 .…”

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confidence: 99%

A chemically driven insulator–metal transition in non-stoichiometric and amorphous gallium oxide

et al. 2008

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Insulator-metal transitions are well known in transition metal oxides, but inducing an insulator-metal transition in the oxide of a main group element is a major challenge. Here we report the observation of an insulator-metal transition, with a conductivity jump of seven orders of magnitude, in highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO 1.2 at a temperature around 670 K. We demonstrate through experimental studies and density-functional-theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric Ga 2 O 3 within the metastable oxide matrix -in chemical terms by a disproportionation. This novel mechanism -an insulator-metal transition driven by a heterogeneous solid state reactionopens up a new route to achieve metallic behaviour in oxides that are expected to exist only as classic insulators.Insulator-metal transitions belong to the most fascinating phenomena in condensed-matter physics 1,2 . Since Mott's landmark work 3,4 it has been known that in crystalline solids strong electron-electron interactions can cause an insulator-metal transition. One example is crystalline Cr-doped vanadium oxide, (V 1-x Cr x ) 2 O 3 , which shows a Mott transition from a paramagnetic Mott insulator to a strongly correlated metal upon an increase in pressure, a lowering of temperature, or a decrease in dopant level 5,6 . In non-crystalline solids structural disorder can also lead to an insulator-metal transition on account of Anderson localization 7 .As shown by Anderson 7 and Mott 8 , in any non-crystalline material the lowest states in the conduction band are localized, i.e. they are electron traps. Only for energies above the mobility edge, E c , do states become non-localized or extended. If the Fermi energy E F is below the mobility edge, states at the Fermi level are localized and the material is an electronic insulator. If, however, the number of electrons increases and the Fermi energy rises above the mobility edge, the material becomes metallic (Anderson transition). As transition metals change their valence state easily, most examples of insulator-metal transitions concern transition metal compounds 4-6,9-11 . The above considerations do not, however, exclude the possibility of inducing an insulator-metal transition in a simple binary oxide of a main group element, even without doping. Instead, large deviations from the ideal stoichiometry, i.e. high defect concentrations, provide a high concentration of electronic defects (self-doping). And if, in addition, the oxide is amorphous, there are two phenomena, strong structural disorder and strong chemical disorder, which could result in an insulator-metal transition.Here we report such a case: Highly non-stoichiometric, amorphous gallium oxide with an approximate chemical composition GaO 1.2 shows an unprecedented insulator-metal transition, with a jump in conductivity of ca. 7 orders of magnitude at temperatures as high as 670 K. We show that this in...

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Metal-Insulator Transition in(V1−xCrx)

Cited by 489 publications

References 51 publications

Dynamical Mean-Field Theory

Dynamical Mean-Field Theory

Spin-1 effective Hamiltonian with three degenerate orbitals: An application to the case of V2O3

A chemically driven insulator–metal transition in non-stoichiometric and amorphous gallium oxide

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