Magnetic polarons in ferromagnetic semiconductor single-electron transistors

N. Lebedeva, A. Varpula, S. Novikov, P. Kuivalainen

Research output: Contribution to journalArticleScientificpeer-review

15 Citations (Scopus)

Abstract

Magnetic polaron (MP) formation is studied theoretically in a single-electron transistor (SET) consisting of a ferromagnetic semiconductor quantum dot (FSQD) coupled to nonmagnetic source, drain, and gate electrodes. Especially, using Green's-function technique we calculate the effect of the gate-voltage-dependent spin polarization of the charge-carrier spins on the magnetization and conductance of the ferromagnetic semiconductor SET in the Coulomb blockade regime. We apply the Anderson impurity model to the FSQD and the ferromagnetic subsystem inside the FSQD is treated in the mean-field approximation. By minimizing the total free energy of the FSQD we calculate the MP binding energy and the dot magnetization as a function of temperature and the gate voltage. The results show that the ferromagnetic transition temperature of the FSQD increases strongly due to the MP formation, which may contribute to the experimentally observed increase in the Curie temperature in the FSQDs. The calculated results also indicate that due to the MP formation the average magnetization of the FSQD can be controlled by the gate voltage in a wide temperature range. Furthermore, our model predicts that the conductance vs gate-voltage curve, which in nonmagnetic SETs shows a symmetric double peak structure, becomes highly asymmetric due to the MP formation.

Original languageEnglish
Article number235307
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume81
Issue number23
DOIs
Publication statusPublished - 8 Jun 2010
MoE publication typeA1 Journal article-refereed

Fingerprint

Single electron transistors
Polarons
single electron transistors
polarons
Gene Conversion
Semiconductor quantum dots
Semiconductor materials
quantum dots
Magnetization
Electric potential
electric potential
magnetization
Coulomb blockade
Spin polarization
Curie temperature
Binding energy
Charge carriers
Green's function
Free energy
Superconducting transition temperature

Cite this

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abstract = "Magnetic polaron (MP) formation is studied theoretically in a single-electron transistor (SET) consisting of a ferromagnetic semiconductor quantum dot (FSQD) coupled to nonmagnetic source, drain, and gate electrodes. Especially, using Green's-function technique we calculate the effect of the gate-voltage-dependent spin polarization of the charge-carrier spins on the magnetization and conductance of the ferromagnetic semiconductor SET in the Coulomb blockade regime. We apply the Anderson impurity model to the FSQD and the ferromagnetic subsystem inside the FSQD is treated in the mean-field approximation. By minimizing the total free energy of the FSQD we calculate the MP binding energy and the dot magnetization as a function of temperature and the gate voltage. The results show that the ferromagnetic transition temperature of the FSQD increases strongly due to the MP formation, which may contribute to the experimentally observed increase in the Curie temperature in the FSQDs. The calculated results also indicate that due to the MP formation the average magnetization of the FSQD can be controlled by the gate voltage in a wide temperature range. Furthermore, our model predicts that the conductance vs gate-voltage curve, which in nonmagnetic SETs shows a symmetric double peak structure, becomes highly asymmetric due to the MP formation.",
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Magnetic polarons in ferromagnetic semiconductor single-electron transistors. / Lebedeva, N.; Varpula, A.; Novikov, S.; Kuivalainen, P.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 81, No. 23, 235307, 08.06.2010.

Research output: Contribution to journalArticleScientificpeer-review

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AU - Lebedeva, N.

AU - Varpula, A.

AU - Novikov, S.

AU - Kuivalainen, P.

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Y1 - 2010/6/8

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AB - Magnetic polaron (MP) formation is studied theoretically in a single-electron transistor (SET) consisting of a ferromagnetic semiconductor quantum dot (FSQD) coupled to nonmagnetic source, drain, and gate electrodes. Especially, using Green's-function technique we calculate the effect of the gate-voltage-dependent spin polarization of the charge-carrier spins on the magnetization and conductance of the ferromagnetic semiconductor SET in the Coulomb blockade regime. We apply the Anderson impurity model to the FSQD and the ferromagnetic subsystem inside the FSQD is treated in the mean-field approximation. By minimizing the total free energy of the FSQD we calculate the MP binding energy and the dot magnetization as a function of temperature and the gate voltage. The results show that the ferromagnetic transition temperature of the FSQD increases strongly due to the MP formation, which may contribute to the experimentally observed increase in the Curie temperature in the FSQDs. The calculated results also indicate that due to the MP formation the average magnetization of the FSQD can be controlled by the gate voltage in a wide temperature range. Furthermore, our model predicts that the conductance vs gate-voltage curve, which in nonmagnetic SETs shows a symmetric double peak structure, becomes highly asymmetric due to the MP formation.

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