Simple treatment of the metal-insulator transition: Effects of degeneracy, temperature, and applied magnetic field

Klejnberg, Andrzej; Spałek, J.

doi:10.1103/physrevb.57.12041

Cited by 42 publications

(39 citation statements)

References 39 publications

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“…This result is in qualitative accordance with the results of work [14], in distinction from [16,21]. Using the critical values of the parameter U/(2w) at which MIT occurs for different integer electron concentrations (see figure 3) we can interpret the fact that in the series of disulphides MS 2 , the CoS 2 (one electron within e g band corresponding to n = 1) and CuS 2 compounds (three electrons within e g -band corresponding n = 3) are metals, and the NiS 2 compound (two electrons within e g -band corresponding n = 2) is an insulator.…”

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confidence: 92%

“…If the exchange interaction is small comparative to the Coulomb interaction J ≪ U, then the splitting is small and leads only to a weak broadening of the bands. Forasmuch we calculate the width of the energy gap we can take into account the effect of J by an appropriate shift of the band center resulting from the inclusion of J into the chemical potential by means of mean-field approximation (see, e.g., [6,14]). …”

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confidence: 99%

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Energy Spectrum of a Doubly Orbitally Degenerate Model With Non-Equivalent Subbands

Didukh¹,

Skorenkyy²,

Dovhopyaty³

2001

Condens. Matter Phys.

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In the present paper we investigate a doubly orbitally degenerate narrowband model with correlated hopping. The model peculiarity takes into account the matrix element of electron-electron interaction which describes intersite hoppings of electrons. In particular, this leads to the concentration dependence of the effective hopping integral. The cases of the strong and weak Hund's coupling are considered. By means of a generalized meanfield approximation the single-particle Green function and quasiparticle energy spectrum are calculated. Metal-insulator transition is studied in the model at different integer values of the electron concentration. Using the obtained energy spectrum we find criteria of metal-insulator transition. : 71.28.+d, 71.27.+a, 71.10.Fd, 71.30.+h Both theoretical analysis [1-3] and available experimental data [4] point out that the Hubbard model [5] should be generalized by taking into account orbital degeneration and correlated hopping. In the present paper we study a metal-insulator transition in the recently proposed [6] doubly orbitally degenerate narrow-band model with correlated hopping. The peculiarity of the model is the electron-hole asymmetry and the dependence of hopping integral on the average number of electrons per site, thus the model shows much better properties than, for example, the Hubbard model with doubly orbital degeneration. The model Hamiltonian is Key words: narrow energy bands, orbital degeneracy, metal-insulator transition, correlated hopping PACS

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confidence: 92%

mentioning

confidence: 99%

Energy Spectrum of a Doubly Orbitally Degenerate Model With Non-Equivalent Subbands

Didukh¹,

Skorenkyy²,

Dovhopyaty³

2001

Condens. Matter Phys.

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“…These interesting experimental findings have stimulated a number of theoretical works on the Mott transitions in the two-orbital Hubbard model by means of DMFT. 12,13,14,15,16,20,21,22,23,24,25,26,27,28,29,30,31,32 Although the two-orbital model has been studied in detail, a systematic study on the systems having more orbitals is still lacking at finite temperatures. For example, the finite-temperature Mott transitions for the multi-orbital Hubbard models has not been investigated quantitatively by DMFT.…”

Section: 2mentioning

confidence: 99%

Finite-temperature Mott transitions in the multiorbital Hubbard model

Koga¹,

Suga²,

Kawakami³

2005

Phys. Rev. B

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We investigate the Mott transitions in the multi-orbital Hubbard model at half-filling by means of the self-energy functional approach. The phase diagrams are obtained at finite temperatures for the Hubbard model with up to four-fold degenerate bands. We discuss how the first-order Mott transition points Uc1 and Uc2 as well as the critical temperature Tc depend on the orbital degeneracy. It is elucidated that enhanced orbital fluctuations play a key role to control the Mott transitions in the multi-orbital Hubbard model.

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“…(11), but also by the orbital JT interactions (13). This results in the separation of the energy scales at finite κ = 0.2t shown in Fig.…”

Section: Numerical Resultsmentioning

confidence: 76%

Orbital Correlations in Monolayer Manganites - From Spin t-J Model to Orbital t-J Model

Daghofer

Oleś

2007

Acta Phys. Pol. A

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On the example of monolayer manganites we show that the theoretical ideas developed long ago along the derivation of the spin t−J model from the Hubbard model are nowadays very helpful in strongly correlated oxides with partly filled degenerate orbitals. We analyze a realistic orbital t−J model for eg electrons in La1−xSr1+xMnO4 monolayer manganites, and discuss the evolution of spin and orbital correlations under increasing doping by performing exact diagonalization of finite clusters, with electronic kinetic energy determined self-consistently at a finite temperature by classical Monte Carlo for t2g spins. Several experimental results are reproduced. Spin t−J modelA new perspective to treat strongly correlated electrons was opened by the derivation of the spin t−J model three decades ago [1]. We argue that this derivation opened new routes to understand the complex magnetic and superconducting instabilities in the Hubbard model, and proved to be a very useful paradigm in strongly correlated electron systems. At that time it was already realized that the Hubbard model,where a † iσ is an electron creation operator in spin state σ =↑, ↓ at site i and U is local Coulomb interaction, is perfectly designed to describe electron localization (497)

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Simple treatment of the metal-insulator transition: Effects of degeneracy, temperature, and applied magnetic field

Cited by 42 publications

References 39 publications

Energy Spectrum of a Doubly Orbitally Degenerate Model With Non-Equivalent Subbands

Energy Spectrum of a Doubly Orbitally Degenerate Model With Non-Equivalent Subbands

Finite-temperature Mott transitions in the multiorbital Hubbard model

Orbital Correlations in Monolayer Manganites - From Spin t-J Model to Orbital t-J Model

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