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Papers by Nguyen Toan Thang

Research paper thumbnail of On the HIGH-TC Superconductivity with Phonon-Mediated Pairing Interaction

We study the effective pairing mediated by O-ion vibration in the high-Tc oxide superconductor, t... more We study the effective pairing mediated by O-ion vibration in the high-Tc oxide superconductor, taking into account two-dimensional screening by the carriers in the CuO2-conducting layers. The effective attractive interaction due to the strong electron-phonon coupling may dominate the one-site repulsion if the latter is strong. The transition temperature Tc is estimated for different pairing symmetries.

Research paper thumbnail of Low Temperature Optics of Semiconductor Quantum Dots

We study the correlation effect in optics of semiconductor quantum dot taking into account on-sit... more We study the correlation effect in optics of semiconductor quantum dot taking into account on-site Coulomb repulsion U in both conduction and valence bands. The midgap excitonic states in the energy spectrum due to Kondo effect is discussed. It is shown that in the small U limit the midgap resonance disappears, while in the large U limit it retains and shifts toward higher energy values.

Research paper thumbnail of Superconducting in the Near Half-Filling Hubbard Model

Modern Physics Letters B, 1995

The Hubbard model of strongly correlated electron systems is considered near half-filling within ... more The Hubbard model of strongly correlated electron systems is considered near half-filling within the framework of a new functional integral method without slave bosons. A dynamical system of equations determining the superconducting phase of the Hubbard model is derived. Both singlet and triplet Cooper pairings are studied.

Research paper thumbnail of Polariton theory of resonant electronic Raman scattering on neutral donor levels in semiconductors with a direct band gap

Journal De Physique, 1980

2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés a... more 2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés aux donneurs neutres dans les semiconducteurs avec une bande interdite directe, quand la fréquence du photon incident est en résonance avec l'exciton. La section efficace de diffusion du polariton avec transition de l'électron de l'état fondamental au premier état excité a été calculée.

Research paper thumbnail of Self-consistent field equations in a two-dimensional model of high-temperature superconductivity with strong carrier correlation

Theoretical and Mathematical Physics, 1989

Research paper thumbnail of Interband Electronic Raman Scattering of Polarized Light in CuCl

Physica Status Solidi B-basic Solid State Physics, 1981

The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photo... more The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photons in the initial and final states and with the transition of the electron from the highest valence band Γ7 to the conduction band Γ6. The exciton effect is taken into account.Es werden die Querschnitte für Ramanstreuung in CuCl mit polarisierten Photonen im Anfangsund Endzustand berechnet für den Übergang eines Elektrons aus dem Valenzband Γ7 in das Leitungsband Γ6. Außerdem werden Exzitoneneffekte berücksichtigt.

Research paper thumbnail of Perturbation Theory of Strongly Correlated Electrons with and without Slave Boson Technique

Journal of The Physical Society of Japan, 1989

The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulom... more The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulomb repulsion were calculated by means of the perturbation theory with respect to the hopping term of the Hamiltonian. It was shown that in the slave boson technique we obtain the expressions different from the results of the calculations involving directly electron operators without using slave bosons. The physical meaning of this discrepancy was discussed.

Research paper thumbnail of Theory of donor electronic Raman scattering in wurtzite-type semiconductors

Research paper thumbnail of Self-consistent field equations in a two-dimensional model of high-temperature superconductivity with strong carrier correlation

Theoretical and Mathematical Physics, 1989

Research paper thumbnail of Some Problems in RVB Theory of HIGH-Tc Superconductivity

International Journal of Modern Physics B, 1988

Title: Some Problems in RVB Theory of HIGH-T c Superconductivity. Authors: van Hieu, Nguyen; Vinh... more Title: Some Problems in RVB Theory of HIGH-T c Superconductivity. Authors: van Hieu, Nguyen; Vinh Tan, Ha; Toan Thang, Nguyen; Ai Viet, Nguyen. Affiliation: AA(Institute of Theoretical Physics, Academy of Science of Vietnam ...

Research paper thumbnail of On the pairing of electrons in superconductors

Theoretical and Mathematical Physics, 1989

A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid ... more A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid with spin-dependent effective interaction potential of the electrons. It is shown by means of Bogolyubov's selfconsistent field method that in the corresponding approximation pairing of electrons with the same helicity occurs. Two different energy gaps appear in the spectrum of quasiparticle excitations.

Research paper thumbnail of On the Role of the Coulomb Interaction of Charge Carriers in the Electronic Raman Scattering on Donor Levels in Direct Band Gap Semiconductors

Physica Status Solidi B-basic Solid State Physics, 1982

The electronic Raman scattering of light on the donor levels in the semiconductors with direct ba... more The electronic Raman scattering of light on the donor levels in the semiconductors with direct band gap is revised, taking into account approximately the Coulomb interaction between the charge carriers (conduction electron and hole). Except for the scattering in the resonance energy domain, where the polariton effect is essential, the influence of the Coulomb interaction of the charge carriers on the scattering cross section is not significant.[Russian Text Ignored].

Research paper thumbnail of Electronic Raman Scattering of Polarized Light on Donor Levels in Semiconductors with Direct Band Gaps

Physica Status Solidi B-basic Solid State Physics, 1980

Explicite approximate analytical expressions are derived for the differential cross sections of t... more Explicite approximate analytical expressions are derived for the differential cross sections of the electronic Raman scattering of circularly polarized light on donor levels with the electronic transition 1s 2s in semiconductors with zincblende structure and direct band gaps. The photon energies are assumed to be nearly equal to the band gap and therefore the intermediate states in the valence bands give dominant contributions. The real symmetry properties of the degenerate valence bands are taken into account. The absolute values of the cross sections are calculated for GaAs.[Russian Text Ignored]

Research paper thumbnail of Theory of donor electronic Raman scattering in wurtzite-type semiconductors

Physical Review B, 1982

A theory is presented for the electronic Raman scattering on donor levels in semiconductors with ... more A theory is presented for the electronic Raman scattering on donor levels in semiconductors with the wurtzite structure. The analytical expressions of the scattering cross section with different photon polarization configurations are derived in the second order of the perturbation theory. A comparison with the experiment is done for CdS.

Research paper thumbnail of Polariton theory of resonant electronic Raman scattering on neutral donor levels in semiconductors with a direct band gap

Journal De Physique, 1980

2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés a... more 2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés aux donneurs neutres dans les semiconducteurs avec une bande interdite directe, quand la fréquence du photon incident est en résonance avec l'exciton. La section efficace de diffusion du polariton avec transition de l'électron de l'état fondamental au premier état excité a été calculée.

Research paper thumbnail of Self-consistent field equations in a two-dimensional model of high-temperature superconductivity with strong carrier correlation

Theoretical and Mathematical Physics, 1989

Research paper thumbnail of Interband electronic Raman scattering of polarized light in cubic semiconductors with degenerate valence bands

Czechoslovak Journal of Physics, 1987

The cross-sections are calculated for the Raman scattering processes with polarized light in cubi... more The cross-sections are calculated for the Raman scattering processes with polarized light in cubic semiconductors whose valence band top is fourfold degenerate γ8. The exciton effect is taken into account.

Research paper thumbnail of Interband Electronic Raman Scattering of Polarized Light in CuCl

Physica Status Solidi B-basic Solid State Physics, 1981

The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photo... more The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photons in the initial and final states and with the transition of the electron from the highest valence band Γ7 to the conduction band Γ6. The exciton effect is taken into account.Es werden die Querschnitte für Ramanstreuung in CuCl mit polarisierten Photonen im Anfangsund Endzustand berechnet für den Übergang eines Elektrons aus dem Valenzband Γ7 in das Leitungsband Γ6. Außerdem werden Exzitoneneffekte berücksichtigt.

Research paper thumbnail of On the pairing of electrons in superconductors

Theoretical and Mathematical Physics, 1989

A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid ... more A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid with spin-dependent effective interaction potential of the electrons. It is shown by means of Bogolyubov's selfconsistent field method that in the corresponding approximation pairing of electrons with the same helicity occurs. Two different energy gaps appear in the spectrum of quasiparticle excitations.

Research paper thumbnail of Perturbation Theory of Strongly Correlated Electrons with and without Slave Boson Technique

Journal of The Physical Society of Japan, 1989

The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulom... more The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulomb repulsion were calculated by means of the perturbation theory with respect to the hopping term of the Hamiltonian. It was shown that in the slave boson technique we obtain the expressions different from the results of the calculations involving directly electron operators without using slave bosons. The physical meaning of this discrepancy was discussed.

Research paper thumbnail of On the HIGH-TC Superconductivity with Phonon-Mediated Pairing Interaction

We study the effective pairing mediated by O-ion vibration in the high-Tc oxide superconductor, t... more We study the effective pairing mediated by O-ion vibration in the high-Tc oxide superconductor, taking into account two-dimensional screening by the carriers in the CuO2-conducting layers. The effective attractive interaction due to the strong electron-phonon coupling may dominate the one-site repulsion if the latter is strong. The transition temperature Tc is estimated for different pairing symmetries.

Research paper thumbnail of Low Temperature Optics of Semiconductor Quantum Dots

We study the correlation effect in optics of semiconductor quantum dot taking into account on-sit... more We study the correlation effect in optics of semiconductor quantum dot taking into account on-site Coulomb repulsion U in both conduction and valence bands. The midgap excitonic states in the energy spectrum due to Kondo effect is discussed. It is shown that in the small U limit the midgap resonance disappears, while in the large U limit it retains and shifts toward higher energy values.

Research paper thumbnail of Superconducting in the Near Half-Filling Hubbard Model

Modern Physics Letters B, 1995

The Hubbard model of strongly correlated electron systems is considered near half-filling within ... more The Hubbard model of strongly correlated electron systems is considered near half-filling within the framework of a new functional integral method without slave bosons. A dynamical system of equations determining the superconducting phase of the Hubbard model is derived. Both singlet and triplet Cooper pairings are studied.

Research paper thumbnail of Polariton theory of resonant electronic Raman scattering on neutral donor levels in semiconductors with a direct band gap

Journal De Physique, 1980

2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés a... more 2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés aux donneurs neutres dans les semiconducteurs avec une bande interdite directe, quand la fréquence du photon incident est en résonance avec l'exciton. La section efficace de diffusion du polariton avec transition de l'électron de l'état fondamental au premier état excité a été calculée.

Research paper thumbnail of Self-consistent field equations in a two-dimensional model of high-temperature superconductivity with strong carrier correlation

Theoretical and Mathematical Physics, 1989

Research paper thumbnail of Interband Electronic Raman Scattering of Polarized Light in CuCl

Physica Status Solidi B-basic Solid State Physics, 1981

The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photo... more The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photons in the initial and final states and with the transition of the electron from the highest valence band Γ7 to the conduction band Γ6. The exciton effect is taken into account.Es werden die Querschnitte für Ramanstreuung in CuCl mit polarisierten Photonen im Anfangsund Endzustand berechnet für den Übergang eines Elektrons aus dem Valenzband Γ7 in das Leitungsband Γ6. Außerdem werden Exzitoneneffekte berücksichtigt.

Research paper thumbnail of Perturbation Theory of Strongly Correlated Electrons with and without Slave Boson Technique

Journal of The Physical Society of Japan, 1989

The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulom... more The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulomb repulsion were calculated by means of the perturbation theory with respect to the hopping term of the Hamiltonian. It was shown that in the slave boson technique we obtain the expressions different from the results of the calculations involving directly electron operators without using slave bosons. The physical meaning of this discrepancy was discussed.

Research paper thumbnail of Theory of donor electronic Raman scattering in wurtzite-type semiconductors

Research paper thumbnail of Self-consistent field equations in a two-dimensional model of high-temperature superconductivity with strong carrier correlation

Theoretical and Mathematical Physics, 1989

Research paper thumbnail of Some Problems in RVB Theory of HIGH-Tc Superconductivity

International Journal of Modern Physics B, 1988

Title: Some Problems in RVB Theory of HIGH-T c Superconductivity. Authors: van Hieu, Nguyen; Vinh... more Title: Some Problems in RVB Theory of HIGH-T c Superconductivity. Authors: van Hieu, Nguyen; Vinh Tan, Ha; Toan Thang, Nguyen; Ai Viet, Nguyen. Affiliation: AA(Institute of Theoretical Physics, Academy of Science of Vietnam ...

Research paper thumbnail of On the pairing of electrons in superconductors

Theoretical and Mathematical Physics, 1989

A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid ... more A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid with spin-dependent effective interaction potential of the electrons. It is shown by means of Bogolyubov's selfconsistent field method that in the corresponding approximation pairing of electrons with the same helicity occurs. Two different energy gaps appear in the spectrum of quasiparticle excitations.

Research paper thumbnail of On the Role of the Coulomb Interaction of Charge Carriers in the Electronic Raman Scattering on Donor Levels in Direct Band Gap Semiconductors

Physica Status Solidi B-basic Solid State Physics, 1982

The electronic Raman scattering of light on the donor levels in the semiconductors with direct ba... more The electronic Raman scattering of light on the donor levels in the semiconductors with direct band gap is revised, taking into account approximately the Coulomb interaction between the charge carriers (conduction electron and hole). Except for the scattering in the resonance energy domain, where the polariton effect is essential, the influence of the Coulomb interaction of the charge carriers on the scattering cross section is not significant.[Russian Text Ignored].

Research paper thumbnail of Electronic Raman Scattering of Polarized Light on Donor Levels in Semiconductors with Direct Band Gaps

Physica Status Solidi B-basic Solid State Physics, 1980

Explicite approximate analytical expressions are derived for the differential cross sections of t... more Explicite approximate analytical expressions are derived for the differential cross sections of the electronic Raman scattering of circularly polarized light on donor levels with the electronic transition 1s 2s in semiconductors with zincblende structure and direct band gaps. The photon energies are assumed to be nearly equal to the band gap and therefore the intermediate states in the valence bands give dominant contributions. The real symmetry properties of the degenerate valence bands are taken into account. The absolute values of the cross sections are calculated for GaAs.[Russian Text Ignored]

Research paper thumbnail of Theory of donor electronic Raman scattering in wurtzite-type semiconductors

Physical Review B, 1982

A theory is presented for the electronic Raman scattering on donor levels in semiconductors with ... more A theory is presented for the electronic Raman scattering on donor levels in semiconductors with the wurtzite structure. The analytical expressions of the scattering cross section with different photon polarization configurations are derived in the second order of the perturbation theory. A comparison with the experiment is done for CdS.

Research paper thumbnail of Polariton theory of resonant electronic Raman scattering on neutral donor levels in semiconductors with a direct band gap

Journal De Physique, 1980

2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés a... more 2014 Dans ce travail nous présentons la théorie de la diffusion de Raman sur les électrons liés aux donneurs neutres dans les semiconducteurs avec une bande interdite directe, quand la fréquence du photon incident est en résonance avec l'exciton. La section efficace de diffusion du polariton avec transition de l'électron de l'état fondamental au premier état excité a été calculée.

Research paper thumbnail of Self-consistent field equations in a two-dimensional model of high-temperature superconductivity with strong carrier correlation

Theoretical and Mathematical Physics, 1989

Research paper thumbnail of Interband electronic Raman scattering of polarized light in cubic semiconductors with degenerate valence bands

Czechoslovak Journal of Physics, 1987

The cross-sections are calculated for the Raman scattering processes with polarized light in cubi... more The cross-sections are calculated for the Raman scattering processes with polarized light in cubic semiconductors whose valence band top is fourfold degenerate γ8. The exciton effect is taken into account.

Research paper thumbnail of Interband Electronic Raman Scattering of Polarized Light in CuCl

Physica Status Solidi B-basic Solid State Physics, 1981

The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photo... more The cross-sections are calculated for the Raman scattering processes in CuCl with polarized photons in the initial and final states and with the transition of the electron from the highest valence band Γ7 to the conduction band Γ6. The exciton effect is taken into account.Es werden die Querschnitte für Ramanstreuung in CuCl mit polarisierten Photonen im Anfangsund Endzustand berechnet für den Übergang eines Elektrons aus dem Valenzband Γ7 in das Leitungsband Γ6. Außerdem werden Exzitoneneffekte berücksichtigt.

Research paper thumbnail of On the pairing of electrons in superconductors

Theoretical and Mathematical Physics, 1989

A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid ... more A study is made of the formation of Cooper pairs in an isotropic superconducting electron liquid with spin-dependent effective interaction potential of the electrons. It is shown by means of Bogolyubov's selfconsistent field method that in the corresponding approximation pairing of electrons with the same helicity occurs. Two different energy gaps appear in the spectrum of quasiparticle excitations.

Research paper thumbnail of Perturbation Theory of Strongly Correlated Electrons with and without Slave Boson Technique

Journal of The Physical Society of Japan, 1989

The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulom... more The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulomb repulsion were calculated by means of the perturbation theory with respect to the hopping term of the Hamiltonian. It was shown that in the slave boson technique we obtain the expressions different from the results of the calculations involving directly electron operators without using slave bosons. The physical meaning of this discrepancy was discussed.