scholarly journals RPA APPROACH TO NON-LINEAR TRANSPORT IN QUANTUM DOTS

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4414-4421
Author(s):  
B. TANATAR ◽  
V. MOLDOVEANU
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Random Phase ◽  
Tight Binding ◽  
Polarization Operator ◽  
Approximation Schemes ◽  
Theoretical Treatment ◽  
Gw Approximation ◽  
Linear Transport ◽  
Non Linear

An accurate theoretical treatment of electron-electron interactions in mesoscopic systems is available in very few cases and approximation schemes are developed in most of the applications, especially for many-level quantum dots. Here we present transport calculations within the random-phase approximation for the Coulomb interaction using the Keldysh Green's functions formalism. We describe the quantum dot systems by a tight-binding Hamiltonian. Our method is similar to the one used by Faleev and Stockman [Phys. Rev. B 66 085318 (2002)] in their study of the equilibrium properties of a homogeneous 2D electron gas. The important extension at the formal level is that we combine the RPA and the Keldysh formalism for studying non-linear transport properties of open quantum dots. Within the Keldysh formalism the polarization operator becomes a contour-ordered quantity that should be computed either from the non-interacting Green functions of the coupled quantum dot (the so-called G0W approximation) either self-consistently (GW approximation). We performed both non-selfconsistent and self-consistent calculations and compare the results. In particular we recover the Coulomb diamonds for interacting quantum dots and we discuss the charge sensing effects in parallel quantum dots.

Spin Blockade in Non-linear Transport through Quantum Dots

1994 ◽  
Vol 26 (6) ◽  
pp. 467-472 ◽  
Author(s):  
D Weinmann ◽  
W Häusler ◽  
W Pfaff ◽  
B Kramer ◽  
U Weiss
Keyword(s):  
Quantum Dots ◽  
Linear Transport ◽  
Non Linear ◽  
Spin Blockade

Transport Properties of Coupled Semiconductor Quantum Dots

2006 ◽  
Vol 6 (11) ◽  
pp. 3329-3332 ◽  
Author(s):  
Heejun Jeong
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Transport Properties ◽  
Electronic Transport ◽  
Low Temperatures ◽  
Spin Interaction ◽  
Many Body ◽  
Conductance Measurement ◽  
Spin Configuration ◽  
Non Linear

We have measured the electronic transport properties of the coupled quantum dot devices at low temperatures. The interplay between the strong many body spin interaction and the molecular states are probed in linear and non-linear transport regime. We observe the formation of strong coherent molecular states clearly visible in the double dot conductance phase diagram. In our study, the spin configuration in multiply coupled quantum dots could be identified using Kondo phenomenon. In addition, the characteristics of the spin dependent molecular states and phase dependant tunneling have been also observed using non-linear conductance measurement of the double dots. The results suggest the importance of the diverse spin related physical issues in artificial quantum dot devices.

scholarly journals Quantum Confined Stark Effect on the Linear and Nonlinear Optical Properties of SiGe/Si Semi Oblate and Prolate Quantum Dots Grown in Si Wetting Layer

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1513
Author(s):  
Varsha ◽  
Mohamed Kria ◽  
Jawad El Hamdaoui ◽  
Laura M. Pérez ◽  
Vinod Prasad ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Dot ◽  
Electric Field ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Wetting Layer ◽  
Non Linear ◽  
Linear Optical Properties ◽  
Linear Optical

We have studied the parallel and perpendicular electric field effects on the system of SiGe prolate and oblate quantum dots numerically, taking into account the wetting layer and quantum dot size effects. Using the effective-mass approximation in the two bands model, we computationally calculated the extensive variation of dipole matrix (DM) elements, bandgap and non-linear optical properties, including absorption coefficients, refractive index changes, second harmonic generation and third harmonic generation as a function of the electric field, wetting layer size and the size of the quantum dot. The redshift is observed for the non-linear optical properties with the increasing electric field and an increase in wetting layer thickness. The sensitivity to the electric field toward the shape of the quantum dot is also observed. This study is resourceful for all the researchers as it provides a pragmatic model by considering oblate and prolate shaped quantum dots by explaining the optical and electronic properties precisely, as a consequence of the confined stark shift and wetting layer.

Non-linear transport through a strongly correlated quantum dot

2012 ◽  
Author(s):  
Martin Nuss ◽  
Enrico Arrigoni ◽  
Wolfgang von der Linden
Keyword(s):  
Quantum Dot ◽  
Strongly Correlated ◽  
Linear Transport ◽  
Non Linear

scholarly journals Electronic properties of α − 𝒯3 quantum dots in magnetic fields

2020 ◽  
Vol 93 (9) ◽  
Author(s):  
Alexander Filusch ◽  
Holger Fehske
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Quantum Dot ◽  
Electronic Properties ◽  
Local Density ◽  
Tight Binding ◽  
Long Wavelength ◽  
Infinite Mass ◽  
Long Wavelength Approximation ◽  
Wavelength Approximation

Abstract We address the electronic properties of quantum dots in the two-dimensional α − 𝒯3 lattice when subjected to a perpendicular magnetic field. Implementing an infinite mass boundary condition, we first solve the eigenvalue problem for an isolated quantum dot in the low-energy, long-wavelength approximation where the system is described by an effective Dirac-like Hamiltonian that interpolates between the graphene (pseudospin 1/2) and Dice (pseudospin 1) limits. Results are compared to a full numerical (finite-mass) tight-binding lattice calculation. In a second step we analyse charge transport through a contacted α − 𝒯3 quantum dot in a magnetic field by calculating the local density of states and the conductance within the kernel polynomial and Landauer-Büttiker approaches. Thereby the influence of a disordered environment is discussed as well. Graphical abstract

Negative differential conductance in non-linear transport of quantum dots

1994 ◽  
Vol 194-196 ◽  
pp. 1325-1326 ◽  
Author(s):  
W. Ha¨usler ◽  
K. Jauregui ◽  
D. Weinmann ◽  
T. Brandes ◽  
B. Kramer
Keyword(s):  
Quantum Dots ◽  
Differential Conductance ◽  
Negative Differential Conductance ◽  
Linear Transport ◽  
Non Linear

Linear and non-linear transport through coupled quantum dots

1996 ◽  
Vol 361-362 ◽  
pp. 636-639 ◽  
Author(s):  
D. Dixon ◽  
L.P. Kouwenhoven ◽  
P.L. McEuen ◽  
Y. Nagamune ◽  
J. Motohisa ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Coupled Quantum Dots ◽  
Linear Transport ◽  
Non Linear

ZEEMAN EFFECT FOR ELECTRONS AND HOLES IN Ge/Si QUANTUM DOTS

2003 ◽  
Vol 02 (06) ◽  
pp. 511-519
Author(s):  
A. V. NENASHEV ◽  
A. V. DVURECHENSKII ◽  
A. F. ZINOVIEVA ◽  
E. A. GOLOVINA
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Zeeman Effect ◽  
Tight Binding ◽  
Growth Direction ◽  
Localized States ◽  
Angular Momentum Projection ◽  
G Factor ◽  
Si Quantum Dot ◽  
Electron And Hole States

We investigate theoretically the Zeeman effect on the electron and hole states in quantum dots. In frame of tight-binding approach, we propose a method of calculating the g factor for localized states. The principal values of the g factor for the ground electron and hole states in the self-assembled Ge / Si quantum dot are calculated. We find the strong g factor anisotropy — the components gxx, gyy are one order smaller than the gzz component, gzz=15.71, gxx=1.14, and gyy=1.76. The analysis of the wave function structure shows that the g factor of hole are mainly controlled by the contribution of the state with Jz=±(3/2), where Jz is the angular momentum projection on the growth direction of the quantum dot. The g factor of localized electron in Ge / Si quantum dot is close to 2: gzz=2.0004 and gxx=gyy=1.9976.

scholarly journals Quantum Dot-like Plasmonic Modes in Twisted Bilayer Graphene Supercells

2D Materials ◽  
2021 ◽  
Author(s):  
T. Westerhout ◽  
Mikhail I Katsnelson ◽  
Malte Rösner
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Random Phase ◽  
System Size ◽  
High Energy ◽  
Bilayer Graphene ◽  
Real Space ◽  
Local Background ◽  
Twisted Bilayer Graphene ◽  
Twisting Angle

Abstract We derive a material-realistic real-space many-body Hamiltonian for twisted bilayer graphene from first principles, including both single-particle hopping terms for $p_z$ electrons and their long-range Coulomb interaction. By disentangling low- and high-energy subspaces of the electronic dispersion, we are able to utilize state-of-the-art constrained Random Phase Approximation calculations to reliably describe the non-local background screening from the high-energy $s$, $p_x$, and $p_y$ electron states which we find to be independent of the bilayer stacking and thus of the twisting angle. The twist-dependent low-energy screening from $p_z$ states is subsequently added to obtain a full screening model. We use this modeling scheme to study plasmons in electron-doped twisted bilayer graphene supercells. We find that the finite system size yields discretized plasmonic levels, which are controlled by the system size, doping level, and twisting angle. This tunability together with atomic-like charge distributions of some of the excitations renders these plasmonic excitations remarkably similar to the electronic states in electronic quantum dots. To emphasize this analogy in the following we refer to these supercells as \emph{plasmonic quantum dots}. Based on a careful comparison to pristine AB-stacked bilayer graphene plasmons, we show that two kinds of plasmonic excitations arise, which differ in their layer polarization. Depending on this layer polarization the resulting plasmonic quantum dot states are either significantly or barely dependent on the twisting angle. Due to their tunability and their coupling to light, these plasmonic quantum dots form a versatile and promising platform for tailored light-matter interactions.

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