| 1. |
- Basylko, S. A., et al.
(författare)
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ac conductivity of a Coulomb glass from computer simulations
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:2, s. 024201-
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Tidskriftsartikel (refereegranskat)abstract
- A method for calculating the photon-induced hopping ac conductivity of a Coulomb glass by computer simulation is proposed. Results obtained by using an effective relaxation algorithm for two three-dimensional models of a Coulomb glass are reported. ac conductance data clearly demonstrate the transition from super-linear to a sub-quadratic power law. We argue that the same qualitative behavior should be expected for compensated semiconductors. It is shown that the transition is driven by the Coulomb energy of sites forming resonant pairs and not by the width of the Coulomb gap.
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| 2. |
- Basylko, S. A., et al.
(författare)
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Coulomb gap in a model with finite charge-transfer energy
- 2001
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 6302:2
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Tidskriftsartikel (refereegranskat)abstract
- The Coulomb gap in a donor-acceptor model with finite charge-transfer energy Delta describing the electronic system on the dielectric side of the metal-insulator transition is investigated by means of computer simulations on two- and three-dimensional finite samples with a random distribution of equal amounts of donor and acceptor sites. Rigorous relations reflecting the symmetry of the model presented with respect to the exchange of donors and accepters are derived. In the immediate neighborhood of the Fermi energy mu. the single-particle density of states g(epsilon) is determined solely by finite size effects, and g(epsilon) further away from mu is described by an asymmetric power law with a nonuniversal exponent, depending on the parameter Delta.
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| 3. |
- Basylko, S. A., et al.
(författare)
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Coulomb glass in the random phase approximation
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:2
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional model of the electrons localized on randomly distributed donor sites of density n and with the acceptor charge uniformly smeared on these sites, -Ke on each, is considered in the random phase approximation (RPA). For the case K = 1/2 the free energy, the density of the one-site energies (DOSE) epsilon, and the pair OSE correlators are found. In the high-temperature region (e(2) n(1/3)/T) < 1 (T is the temperature) RPA energies and DOSE are in a good agreement with the corresponding data of Monte Carlo simulations. Thermodynamics of the model in this region is similar to the one of an electrolyte in the regime of Debye screening. In the vicinity of the Fermi level μ = 0 the OSE correlations, depending on sgn(ε(1) . ε(2)) and with very slow decoupling law, have been found. The main result is that even in the temperature range where the energy of a Coulomb glass is determined by Debye screening effects, the correlations of the long-range nature between the OSE still exist.
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| 4. |
- Basylko, S. A., et al.
(författare)
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Coulomb glass in the restricted random phase approximation
- 2002
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Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 298:06-maj, s. 416-421
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional model of N/2 electrons localized on N randomly distributed donor sites of density n and with the acceptor charge uniformly smeared on these sites, -e/2 on each. has been considered in the restricted random phase approximation (RRPA) which uses the set of 3N Fourier components of the local charge density as the independent collective variables. The energy e(T) per site and the density of one-site excitation energy (DOSE) g(epsilon) are shown to he, respectively, in excellent quantitative and in good qualitative agreement with the Monte Carlo simulation data in the whole temperature region 0.1 < T < 100, where these simulations were performed (e(2)n(1/3)/k(B) being the temperature scale). The pair correlator for the one-site energies g(epsilon,+/-epsilon, r) is found to have the slow decoupling law similar to(+/-1/r) for T less than or similar to 1 and r much greater than r(d) (r(d), Debye screening radius). The status of the commonly accepted asymptotic g(epsilon) similar to (epsilon - mu)(d-1) (d and mu being, respectively, the spatial dimension and the Fermi energy) is discussed. The deduction of this asymptotic is shown to be based on the strong and questionable conjecture about decoupling of correlations between one-site excitation energies in the vicinity of mu.
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| 5. |
- Basylko, S. A., et al.
(författare)
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Ground-state study of a donor-acceptor model with finite charge-transfer energy
- 2000
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Ingår i: Physics Letters A. - 0375-9601 .- 1873-2429. ; 271:02-jan, s. 134-138
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Tidskriftsartikel (refereegranskat)abstract
- A donor-acceptor model with randomly distributed N donor and N acceptor sites and with finite charge transfer energy Delta is investigated at zero temperature by means of computer simulations on two-dimensional samples of different sizes, We demonstrate that the density of one-electron excitations g(epsilon) for accepters in the vicinity of the Fermi energy mu depends essentially on the size of the sample investigated and that g(epsilon) further away from mu exhibits a size-independent power-law with the non-universal exponent decreasing with increasing Delta. Rigorous relations for mu and for the mapping of g(epsilon) for donors into g(epsilon) for accepters are also given.
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| 6. |
- Basylko, S. A., et al.
(författare)
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One-dimensional Kondo lattice model studied through numerical diagonalization
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:7
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Tidskriftsartikel (refereegranskat)abstract
- The one-dimensional Kondo lattice model is studied by means of the numerical diagonalization method. By using massively parallel computations, we were able to study lattices large enough to obtain convergent results for electron densities n <= 2/3. For such densities, an additional ferromagnetic region is found inside the paramagnetic phase. Also, a region is found where the localized spins participate in the low-energy dynamics together with the conduction electrons, thus resulting in a large Fermi surface. These results are an independent confirmation of previous density matrix renormalization group results.
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