scholarly journals Enhanced Negative Nonlocal Conductance in an Interacting Quantum Dot Connected to Two Ferromagnetic Leads and One Superconducting Lead

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 1003 ◽  
Author(s):  
Cong Lee ◽  
Bing Dong ◽  
Xiao-Lin Lei
Keyword(s):  
Quantum Dot ◽  
Spin Polarization ◽  
Electronic Transport ◽  
Andreev Reflection ◽  
Mean Field ◽  
Function Technique ◽  
Field Approach ◽  
Tunnel Coupling ◽  
Nonequilibrium Green Function ◽  
Parallel Configuration

In this paper, we investigate the electronic transport properties of a quantum dot (QD) connected to two ferromagnetic leads and one superconducting lead in the Kondo regime by means of the finite-U slave boson mean field approach and the nonequilibrium Green function technique. In this three-terminal hybrid nanodevice, we focus our attention on the joint effects of the Kondo correlation, superconducting proximity pairing, and spin polarization of leads. It is found that the superconducting proximity effect will suppress the linear local conductance (LLC) stemming from the weakened Kondo peak, and when its coupling Γ s is bigger than the tunnel-coupling Γ of two normal leads, the linear cross conductance (LCC) becomes negative in the Kondo region. Regarding the antiparallel configuration, increasing spin polarization further suppresses LLC but enhances LCC, i.e., causing larger negative values of LCC, since it is beneficial for the emergence of cross Andreev reflection. On the contrary, for the parallel configuration, with increasing spin polarization, the LLC decreases and greatly widens with the appearance of shoulders, and eventually splits into four peaks, while the LCC decreases relatively rapidly to the normal conductance.

scholarly journals Spin Polarization and Exchange Interaction in a Diluted Magnetic Qunautm Dot

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
A. John Peter ◽  
K. Lily Mary Eucharista
Keyword(s):  
Field Theory ◽  
Quantum Dot ◽  
Spin Polarization ◽  
Ionization Energy ◽  
Mean Field Theory ◽  
Mean Field ◽  
Binding Energies ◽  
Spin Interaction ◽  
Itinerant Electron ◽  
Diluted Magnetic

The spin interaction energy of differentMn2+ions with and without an itinerant electron is evaluated for different dot radii. Magnetization is calculated for various concentrations ofMn2+ions with different dot sizes. Spin polaronic shifts are estimated using a mean field theory. The lowest binding energies of electrons in aCd1-xMnxTequantum dot are also calculated. Results are obtained forCd1−xinMnxinTe/Cd1−xoutMnxoutTestructures as a function of the dot radius variationally. It is found that (i) more number ofMn2+spins enhance the spin polaronic effect and it varies linearly with the concentration, (ii) spin polarization ofMn2+ions increases with the concentration for any dot radii, (iii) the magnetization of Mn subsystem increases with the concentration ofMn2+ions and this feature is predominant for smaller dots, and (iv) variation of increase in ionization energy is sharper for smaller dots with increase in concentration. These results are discussed with the available data in literature.

Capacitance of InAs quantum dot arrays in a mean field approach

1998 ◽  
Vol 249-251 ◽  
pp. 271-275 ◽  
Author(s):  
O. Heller ◽  
Ph. Lelong ◽  
G. Bastard
Keyword(s):  
Quantum Dot ◽  
Mean Field ◽  
Field Approach ◽  
Inas Quantum Dot

scholarly journals Dicke and Fano-Andreev reflections in a triple quantum-dot system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. González I. ◽  
M. Pacheco ◽  
A. M. Calle ◽  
E. C. Siqueira ◽  
P. A. Orellana
Keyword(s):  
Quantum Dot ◽  
Electronic Transport ◽  
Linear Response ◽  
Quantum Interference ◽  
Andreev Reflection ◽  
Interference Effects ◽  
Anderson Hamiltonian ◽  
Abrupt Changes ◽  
Non Equilibrium Green’S Function ◽  
Non Equilibrium

AbstractThis article studies quantum interference effects and their influence on the electronic transport through a parallel triple quantum-dot system coupled to normal and superconducting leads in the linear response and non-equilibrium regime. We model the system by a triple impurity Anderson Hamiltonian including the Coulomb intra-dot correlations in all quantum-dots. Using the non-equilibrium Green’s function formalism, we calculate the Andreev conductance and the transmittance for energies within the superconductor gap. Our results show that the Andreev reflection spectra, both in the presence and absence of Coulomb interaction, reveal Fano and Dicke-like resonances in analogy to the Fano and Dicke effects in atomic physics. As one of the main results, we obtain that the charge shows abrupt changes due to the Dicke effect.

A NONSELF-CONSISTENT METHOD FOR THE NONEQUILIBRIUM GREEN'S FUNCTION TECHNIQUE

2009 ◽  
Vol 08 (03) ◽  
pp. 423-431
Author(s):  
Z. Z. SUN ◽  
W. FAN ◽  
R. Q. ZHANG
Keyword(s):  
Energy Level ◽  
Electronic Transport ◽  
Transport Systems ◽  
Function Technique ◽  
Electron Interaction ◽  
Many Body ◽  
Consistent Method ◽  
Nonequilibrium Green Function ◽  
The Many ◽  
Parametric Approximation

A parametric approximation approach is proposed to study the electronic transport properties in quantum transport systems such as quantum dots and molecules. This approach is developed from the nonequilibrium Green function technique and employs an approximate nonself-consistent (NSC) procedure to substitute the original self-consistent (SC) one when the many-body term, such as electron–electron interaction, is considered. A simple model of one eigen-energy level coupled to two continuous energy spectrums is used to illustrate the new NSC method that can be generalized to multi-energy level cases in a straightforward manner. The comparison between the NSC results with the SC results demonstrate the correctness and the effectiveness of the new method.

scholarly journals Polaron Relaxation In A Quantum Dot Due To Anharmonic Coupling Within A Mean-Field Approach

2010 ◽  
Author(s):  
T. Stauber ◽  
M. I. Vasilevskiy ◽  
S. S. Makler ◽  
E. V. Anda ◽  
Marília Caldas ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Mean Field ◽  
Field Approach ◽  
Anharmonic Coupling

Controllable Spin-Polarization of Electronic Transport through a Magnetic Quantum Dot in the Influence of Microwave Field

2010 ◽  
Vol 663-665 ◽  
pp. 466-469
Author(s):  
Yun Qing Zhou ◽  
Jian Ming Yao ◽  
Ling Min Kong ◽  
Rui Wang
Keyword(s):  
Quantum Dot ◽  
Spin Polarization ◽  
Electronic Transport ◽  
Resonant Tunneling ◽  
Microwave Field ◽  
Evolution Operator ◽  
Tunneling Current ◽  
Operator Method ◽  
Main Peak ◽  
Energy Distance

The evolution operator method is applied to studying the time-dependent and spin-related electron transport through a magnetic quantum dot coupled to two normal-metal leads. When the microwave field is applied on quantum dot there are additional peaks of PAT current besides the main peak of resonant tunneling current, and the energy distance between peaks relate to the frequency of microwave fields. Furthermore, owe to the spin non-degeneration in the magnetic quantum dot, the spin-up and spin-down current peaks are separated, and the separated distance depends on Zeeman energy. These effects allow us to propose a scheme to control the magnitude and spin polarization of current.

MESOSCOPIC TRANSPORT THROUGH A QUANTUM-DOT-EMBEDDED AHARONOV–BOHM RING THREADED WITH AC FLUX

2001 ◽  
Vol 15 (08) ◽  
pp. 1177-1192 ◽  
Author(s):  
HONG-KANG ZHAO
Keyword(s):  
Quantum Dot ◽  
Tunneling Current ◽  
Differential Conductance ◽  
Function Technique ◽  
Zero Temperature ◽  
Mesoscopic Transport ◽  
Conductance Oscillation ◽  
Nonequilibrium Green Function ◽  
Multi Level ◽  
Aharonov Bohm

The electron transporting through a mesoscopic ring embedded with one quantum dot and threaded by dc and ac magnetic fluxes is investigated by employing the Keldysh nonequilibrium Green function technique. The tunneling current and differential conductance are derived to show the Aharonov–Bohm-like effect induced by external magnetic fluxes. The multi-channel ring and multi-level quantum dot system is studied. The quenching and nonmonotone effects versus the magnitude of ac flux are revealed in differential conductance. This signifies that at some values of ac flux, the tunneling current may be suppressed or enhanced. The differential conductance oscillation and I-V characteristics are studied numerically at zero temperature. The aperiodically nonmonotonical conductance versus the magnitude of ac flux, multi-channel negative differential conductance, photon-electron pump effect are also observed.

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