Search results

1

Optically Induced Gaps in Disordered Semiconductors

100%

Kalvová A., Velický B.

Acta Physica Polonica A

|

1996

|

vol. 90

|

issue 4

837-842

EN

On the example of an explicitly solvable model of a semiconductor with alloy disorder in the conduction band, it is shown that a slowly varying exciting light pulse can be treated in an adiabatic approximation, that is, the self-energy of an electron can be taken as a continuously evolving series of snapshots of self-energies corresponding to a steady illumination with the instantaneous value of the light strength.

2

Magnetism Within the Limitations of the LDA Band Structure Calculations

100%

Szpunar B.

Acta Physica Polonica A

|

1993

|

vol. 84

|

issue 1

21-42

EN

We discuss the limitations of the local density approximation for high-temperature superconductors and related to them parent antiferromagnetic insulators. The calculated band-gap accuracy is pointed out for two cases: C_{60}-FCC and YBa_{2}Cu_{3}O_{6}. We also compare the results for parent CaCuO_{2} and NiO systems, as well as discuss the role of gradient and self-energy (GW) corrections for the Mott insulators.

3

Electronic Structure and Fermiology of High-T_{c} Superconductors

80%

Bansil A., Kaprzyk S.

Acta Physica Polonica A

|

1993

|

vol. 84

|

issue 1

7-20

EN

We briefly discuss some of our recent results in three areas, all related to issues concerning the electronic structure and fermiology of the high-T_{c}'s. (i) First-principles band theory based computations of the electron-positron momentum density relevant for the interpretation of the positron annihilation (2D-ACAR) experiments; results for YBa_{2}Cu_{3}O_{7} are discussed. (ii) Another k-resolved spectroscopy where such first-principles comparisons between the computed and measured spectral intensities have been crucially important is the angle-resolved photoemission experiment; we discuss results for the (001)-surface of YBa_{2}Cu_{3}O_{7} where computations yield considerable insight into the nature and origin of the spectral signal associated with the CuO_{2} plane bands. (iii) The study of effects of substitutions and of oxygen-vacancy disorder in the high-T_{c}'s; here results for the LaSrCuO_{4}, and Ba-K-Bi-O and Ba-Pb-Bi-O systems, with focus on the nature of the van Hove singularity in the vicinity of the Fermi energy are presented.

4

Ultrafast Dynamics and Quantum Transport of Electrons in Strongly Disordered Semiconductors

80%

Kalvová A., Velický B.

Acta Physica Polonica A

|

1995

|

vol. 88

|

issue 4

767-770

EN

The new experiments on the response of electrons in semiconductors to femtosecond optical pulses call for developing adequate theoretical tools. A promising approach has been found in using the non-equilibrium Green functions approximately factorized on the basis of the so-called generalized Kadanoff-Baym ansatz. The present work investigates the validity of such approach on an example of a semiconductor with an alloy scattering, where the coherent potential approximation allows to construct the non-equilibrium Green functions directly, so that an explicit comparison with the ansatz decoupling is possible. The ansatz for the electron distribution is in this case justified as far as the quasiparticle picture for the individual electrons is appropriate.

Refine search results

4 Acta Physica Polonica A

1 1996

1 1995

2 1993

2 Kalvová A.

2 Velický B.

1 Bansil A.

1 Kaprzyk S.

1 Szpunar B.

Optically Induced Gaps in Disordered Semiconductors

Magnetism Within the Limitations of the LDA Band Structure Calculations

Electronic Structure and Fermiology of High-T_{c} Superconductors

Ultrafast Dynamics and Quantum Transport of Electrons in Strongly Disordered Semiconductors