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 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.

Quantum-dot Cellular Automata

2001 ◽  
Vol 696 ◽  
Author(s):  
Gregory L. Snider ◽  
Alexei O. Orlov ◽  
Ravi K. Kummamuru ◽  
Rajagopal Ramasubramaniam ◽  
Islamshah Amlani ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Cellular Automata ◽  
Quantum Dot ◽  
Low Temperatures ◽  
Tunnel Junctions ◽  
Operating Temperature ◽  
Building Blocks ◽  
Quantum Dot Cellular Automata ◽  
Background Charge ◽  
Metal Islands

AbstractAn overview is given of the quantum-dot cellular automata (QCA) architecture, along with a summary of experimental demonstrations of QCA devices. QCA is a transistorless computation paradigm that can provide a solution to such challenging issues as device and power density. The basic building blocks of the QCA architecture, such as AND, OR gates and clocked cells have been demonstrated and will be presented here. The quantum dots used in the experiments to date are metal islands that are coupled by capacitors and tunnel junctions, and devices operate only at very low temperatures. For QCA to be used in practical devices, the operating temperature must be raised, and issues such as background charge must be addressed. An introduction will be given to these issues and possible solutions.

Electronic transport properties of UCu4+xAl8−x at low temperatures

1990 ◽  
Vol 165-166 ◽  
pp. 429-430 ◽  
Author(s):  
R. Köhler ◽  
C. Geibel ◽  
S. Horn ◽  
B. Strobel ◽  
S. Arnold ◽  
...  
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
Low Temperatures ◽  
Electronic Transport Properties

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.

scholarly journals Coefficient of Interband Light Absorption by InAs/GaхIn1-хAs Quantum Dot Superlattice at Low Temperatures

2017 ◽  
Vol 18 (2) ◽  
pp. 151-157
Author(s):  
V.I. Boichuk ◽  
I.V. Bilynsky ◽  
R.I. Pazyuk
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Absorption Coefficient ◽  
Light Absorption ◽  
Low Temperatures ◽  
Dispersion Relations ◽  
Interband Absorption ◽  
Absorption Bands ◽  
Interband Light Absorption

In the paper the InAs/GaxIn1-xAs superlattice system of small size cubic QDs (10 nm) has been considered. Dispersion relations for electron and hole subbands have been calculated for superlattices of different dimensionality. The dependences of the interband absorption coefficient on light frequency, quantum dot size and interdot distance have been researched.It is shown, that the dimension of the superlattice has influence on the shape of the absorption bands and the increasingof the distance between quantum dots is followed by narrowing of the absorption peaks for all three superlatticetypes.

scholarly journals Current Fluctuations in Hybrid-Superconductor Normal Structures with Quantum Dots

2021 ◽  
Author(s):  
◽  
Stephanie Droste
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Electronic Transport ◽  
Proximity Effect ◽  
Noise Spectrum ◽  
Current Fluctuations ◽  
Cooper Pairs ◽  
Finite Frequency ◽  
Strong Coulomb ◽  
Superconducting Correlations

<p>Nanostructures with quantum dots in proximity to superconducting electrodes are an ideal tool to study superconducting correlations in systems with few degrees of freedom that exhibit strong Coulomb-interaction effects. Such hybrid superconductor-normal structures show rich physics due to the interplay of superconductivity, Coulomb interaction and non-equilibrium. Superconducting correlations are established on the quantum dot when it is coupled to a superconductor even in the presence of strong Coulomb repulsion and Cooper pairs can tunnel coherently between the quantum dot and the superconductor.  In this thesis, we investigate theoretically electronic transport through an interacting quantum dot coupled to normal and superconducting leads. The presence of the proximity effect can be detected by the dot's current, namely the Andreev current. However, current fluctuations might reveal information on the electronic transport and the internal structure of the system which is not visible in the mean value of the current. For this reason, we study the current fluctuations through the proximized quantum dot to get access to the properties of such a hybrid quantum-dot system. In particular, we are interested in the finite-frequency fluctuations to unveil the coherent dynamics underlying the proximity effect in the quantum dot and its internal time scales.  At first, we present a study of the frequency-dependent current noise for subgap transport through an interacting single-level quantum dot tunnel-coupled to normal and superconducting leads. For this purpose, we employ a non-equilibrium diagrammatic real-time approach to calculate the finite-frequency current noise. The finite-frequency noise spectrum shows a sharp dip at a frequency corresponding to the energy splitting of the Andreev bound states which is a signature of the coherent exchange of Cooper pairs between the quantum dot and the superconductor. Furthermore, in the high frequency regime, the so called quantum noise regime, the noise spectrum exhibits steps at frequencies equal to the excitation energies. These steps can be related to the effective coupling strength of the excitations.  However, the statistical description of the electron transport does not stop with the noise. Current cumulants of arbitrary order can be obtained by means of full counting statistics (FCS). We set up a theory based on the diagrammatic real-time approach to calculate the finite-time FCS for quantum transport with a non-Markovian master equation that captures the initial correlations between system and reservoir. This allows us to fully describe the current fluctuations of the hybrid quantum-dot system, that is the noise and all higher order current cumulants.</p>

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