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Quantum Transport in Mesoscopic Systems
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Quantum Transport in Mesoscopic Systems

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Quantum Information".

Deadline for manuscript submissions: closed (15 December 2019) | Viewed by 65821

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. David Sánchez

E-Mail Website
Guest Editor
Institute for Cross-Disciplinary Physics and Complex Systems IFISC (UIB-CSIC), E-07122 Palma de Mallorca, Spain
Interests: quantum transport; quantum thermodynamics; thermoelectrics; spintronics; strongly correlated systems; language variation and change
Dr. Michael Moskalets

E-Mail Website
Guest Editor
Department of Metal and Semiconductor Physics, NTU “Kharkiv Polytechnic Institute”, 61002 Kharkiv, Ukraine
Interests: quantum pumping; quantum coherent electronics; dynamical heat transport

Special Issue Information

Dear Colleagues,

Mesoscopic physics has now become a well-established, mature field. The techniques developed in the 1980s and 1990s to understand electronic transport in small conductors form a standard toolbox that is available for theoreticians and experimentalists alike. Importantly, the electrical properties of mesoscopic conductors happen to be governed directly by the quantum properties of carriers, hence the term “quantum transport”. However, the advent of new materials with exotic properties poses serious challenges for the understanding of novel phenomena using standard formalisms. Further, today’s possibility of designing different setups and measurement schemes offers the opportunity of investigating transport effects lying at the interface between condensed matter, thermodynamics, and quantum information. This issue attempts to review recent trends in quantum transport and mesoscopics with a rich variety of topics: nanoscale heat and dissipation, coherent single-electronics, semiconductor spintronics, topological quantum matter, quantum Hall effects, graphene structures, strongly interacting systems, noise and fluctuations, etc.

Dr. David Sánchez
Dr. Michael Moskalets
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Entropy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (19 papers)

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Editorial

Jump to: Research, Review

4 pages, 187 KiB  
Editorial
Quantum Transport in Mesoscopic Systems
by David Sánchez and Michael Moskalets
Entropy 2020, 22(9), 977; https://doi.org/10.3390/e22090977 - 01 Sep 2020
Cited by 4 | Viewed by 2853
Abstract
Mesoscopic physics has become a mature field [...] Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)

Research

Jump to: Editorial, Review

17 pages, 1283 KiB  
Article
Effective Equilibrium in Out-of-Equilibrium Interacting Coupled Nanoconductors
by Lucas Maisel and Rosa López
Entropy 2020, 22(1), 8; https://doi.org/10.3390/e22010008 - 19 Dec 2019
Cited by 2 | Viewed by 2297
Abstract
In the present work, we study a mesoscopic system consisting of a double quantum dot in which both quantum dots or artificial atoms are electrostatically coupled. Each dot is additionally tunnel coupled to two electronic reservoirs and driven far from equilibrium by external [...] Read more.
In the present work, we study a mesoscopic system consisting of a double quantum dot in which both quantum dots or artificial atoms are electrostatically coupled. Each dot is additionally tunnel coupled to two electronic reservoirs and driven far from equilibrium by external voltage differences. Our objective is to find configurations of these biases such that the current through one of the dots vanishes. In this situation, the validity of the fluctuation–dissipation theorem and Onsager’s reciprocity relations has been established. In our analysis, we employ a master equation formalism for a minimum model of four charge states, and limit ourselves to the sequential tunneling regime. We numerically study those configurations far from equilibrium for which we obtain a stalling current. In this scenario, we explicitly verify the fluctuation–dissipation theorem, as well as Onsager’s reciprocity relations, which are originally formulated for systems in which quantum transport takes place in the linear regime. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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25 pages, 4086 KiB  
Article
Stochastic Schrödinger Equations and Conditional States: A General Non-Markovian Quantum Electron Transport Simulator for THz Electronics
by Devashish Pandey, Enrique Colomés, Guillermo Albareda and Xavier Oriols
Entropy 2019, 21(12), 1148; https://doi.org/10.3390/e21121148 - 25 Nov 2019
Cited by 8 | Viewed by 3039
Abstract
A prominent tool to study the dynamics of open quantum systems is the reduced density matrix. Yet, approaching open quantum systems by means of state vectors has well known computational advantages. In this respect, the physical meaning of the so-called conditional states in [...] Read more.
A prominent tool to study the dynamics of open quantum systems is the reduced density matrix. Yet, approaching open quantum systems by means of state vectors has well known computational advantages. In this respect, the physical meaning of the so-called conditional states in Markovian and non-Markovian scenarios has been a topic of recent debate in the construction of stochastic Schrödinger equations. We shed light on this discussion by acknowledging the Bohmian conditional wavefunction (linked to the corresponding Bohmian trajectory) as the proper mathematical object to represent, in terms of state vectors, an arbitrary subset of degrees of freedom. As an example of the practical utility of these states, we present a time-dependent quantum Monte Carlo algorithm to describe electron transport in open quantum systems under general (Markovian or non-Markovian) conditions. By making the most of trajectory-based and wavefunction methods, the resulting simulation technique extends to the quantum regime, the computational capabilities that the Monte Carlo solution of the Boltzmann transport equation offers for semi-classical electron devices. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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16 pages, 856 KiB  
Article
Enhanced Negative Nonlocal Conductance in an Interacting Quantum Dot Connected to Two Ferromagnetic Leads and One Superconducting Lead
by Cong Lee, Bing Dong and Xiao-Lin Lei
Entropy 2019, 21(10), 1003; https://doi.org/10.3390/e21101003 - 14 Oct 2019
Cited by 1 | Viewed by 2398
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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21 pages, 1180 KiB  
Article
Nonadiabaticity in Quantum Pumping Phenomena under Relaxation
by Kazunari Hashimoto and Chikako Uchiyama
Entropy 2019, 21(9), 842; https://doi.org/10.3390/e21090842 - 28 Aug 2019
Cited by 2 | Viewed by 2526
Abstract
The ability to control quanta shown by quantum pumping has been intensively studied, aiming to further develop nano fabrication. In accordance with the fast progress of the experimental techniques, the focus on quantum pumping extends to include the quicker transport. For this purpose, [...] Read more.
The ability to control quanta shown by quantum pumping has been intensively studied, aiming to further develop nano fabrication. In accordance with the fast progress of the experimental techniques, the focus on quantum pumping extends to include the quicker transport. For this purpose, it is necessary to remove the “adiabatic” or “slow” condition, which has been the central concept of quantum pumping since its first proposal for a closed system. In this article, we review the studies which go beyond the conventional adiabatic approximation for open quantum systems to transfer energy quanta and electron spins with using the full counting statistics. We also discuss the recent developments of the nonadiabatic treatments of quantum pumping. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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22 pages, 1202 KiB  
Article
Quantum Adiabatic Pumping in Rashba- Dresselhaus-Aharonov-Bohm Interferometer
by Yasuhiro Tokura
Entropy 2019, 21(9), 828; https://doi.org/10.3390/e21090828 - 24 Aug 2019
Cited by 1 | Viewed by 2689
Abstract
We investigate the quantum adiabatic pumping effect in an interferometer attached to two one-dimensional leads. The interferometer is subjected to an Aharonov-Bohm flux and Rashba-Dresselhaus spin-orbit interaction. Using Brouwer’s formula and rigorous scattering eigenstates, we obtained the general closed formula for the pumping [...] Read more.
We investigate the quantum adiabatic pumping effect in an interferometer attached to two one-dimensional leads. The interferometer is subjected to an Aharonov-Bohm flux and Rashba-Dresselhaus spin-orbit interaction. Using Brouwer’s formula and rigorous scattering eigenstates, we obtained the general closed formula for the pumping Berry curvatures depending on spin for general interferometers when the external control parameters only modulate the scattering eigenstates and corresponding eigenvalues. In this situation, pumping effect is absent in the combination of the control parameters of Aharonov-Bohm flux and spin-orbit interaction strength. We have shown that finite pumping is possible by modulating both Rashba and Dresselhaus interaction strengths and explicitly demonstrated the spin-pumping effect in a diamond-shaped interferometer made of four sites. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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30 pages, 1178 KiB  
Article
Thermodynamics and Steady State of Quantum Motors and Pumps Far from Equilibrium
by Raúl A. Bustos-Marún and Hernán L. Calvo
Entropy 2019, 21(9), 824; https://doi.org/10.3390/e21090824 - 23 Aug 2019
Cited by 16 | Viewed by 4429
Abstract
In this article, we briefly review the dynamical and thermodynamical aspects of different forms of quantum motors and quantum pumps. We then extend previous results to provide new theoretical tools for a systematic study of those phenomena at far-from-equilibrium conditions. We mainly focus [...] Read more.
In this article, we briefly review the dynamical and thermodynamical aspects of different forms of quantum motors and quantum pumps. We then extend previous results to provide new theoretical tools for a systematic study of those phenomena at far-from-equilibrium conditions. We mainly focus on two key topics: (1) The steady-state regime of quantum motors and pumps, paying particular attention to the role of higher order terms in the nonadiabatic expansion of the current-induced forces. (2) The thermodynamical properties of such systems, emphasizing systematic ways of studying the relationship between different energy fluxes (charge and heat currents and mechanical power) passing through the system when beyond-first-order expansions are required. We derive a general order-by-order scheme based on energy conservation to rationalize how every order of the expansion of one form of energy flux is connected with the others. We use this approach to give a physical interpretation of the leading terms of the expansion. Finally, we illustrate the above-discussed topics in a double quantum dot within the Coulomb-blockade regime and capacitively coupled to a mechanical rotor. We find many exciting features of this system for arbitrary nonequilibrium conditions: a definite parity of the expansion coefficients with respect to the voltage or temperature biases; negative friction coefficients; and the fact that, under fixed parameters, the device can exhibit multiple steady states where it may operate as a quantum motor or as a quantum pump, depending on the initial conditions. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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18 pages, 1620 KiB  
Article
Power, Efficiency and Fluctuations in a Quantum Point Contact as Steady-State Thermoelectric Heat Engine
by Sara Kheradsoud, Nastaran Dashti, Maciej Misiorny, Patrick P. Potts, Janine Splettstoesser and Peter Samuelsson
Entropy 2019, 21(8), 777; https://doi.org/10.3390/e21080777 - 08 Aug 2019
Cited by 31 | Viewed by 4136
Abstract
The trade-off between large power output, high efficiency and small fluctuations in the operation of heat engines has recently received interest in the context of thermodynamic uncertainty relations (TURs). Here we provide a concrete illustration of this trade-off by theoretically investigating the operation [...] Read more.
The trade-off between large power output, high efficiency and small fluctuations in the operation of heat engines has recently received interest in the context of thermodynamic uncertainty relations (TURs). Here we provide a concrete illustration of this trade-off by theoretically investigating the operation of a quantum point contact (QPC) with an energy-dependent transmission function as a steady-state thermoelectric heat engine. As a starting point, we review and extend previous analysis of the power production and efficiency. Thereafter the power fluctuations and the bound jointly imposed on the power, efficiency, and fluctuations by the TURs are analyzed as additional performance quantifiers. We allow for arbitrary smoothness of the transmission probability of the QPC, which exhibits a close to step-like dependence in energy, and consider both the linear and the non-linear regime of operation. It is found that for a broad range of parameters, the power production reaches nearly its theoretical maximum value, with efficiencies more than half of the Carnot efficiency and at the same time with rather small fluctuations. Moreover, we show that by demanding a non-zero power production, in the linear regime a stronger TUR can be formulated in terms of the thermoelectric figure of merit. Interestingly, this bound holds also in a wide parameter regime beyond linear response for our QPC device. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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15 pages, 406 KiB  
Article
On the Role of Local Many-Body Interactions on the Thermoelectric Properties of Fullerene Junctions
by Carmine Antonio Perroni and Vittorio Cataudella
Entropy 2019, 21(8), 754; https://doi.org/10.3390/e21080754 - 01 Aug 2019
Cited by 1 | Viewed by 2289
Abstract
The role of local electron–vibration and electron–electron interactions on the thermoelectric properties of molecular junctions is theoretically analyzed focusing on devices based on fullerene molecules. A self-consistent adiabatic approach is used in order to obtain a non-perturbative treatment of the electron coupling to [...] Read more.
The role of local electron–vibration and electron–electron interactions on the thermoelectric properties of molecular junctions is theoretically analyzed focusing on devices based on fullerene molecules. A self-consistent adiabatic approach is used in order to obtain a non-perturbative treatment of the electron coupling to low frequency vibrational modes, such as those of the molecule center of mass between metallic leads. The approach also incorporates the effects of strong electron–electron interactions between molecular degrees of freedom within the Coulomb blockade regime. The analysis is based on a one-level model which takes into account the relevant transport level of fullerene and its alignment to the chemical potential of the leads. We demonstrate that only the combined effect of local electron–vibration and electron–electron interactions is able to predict the correct behavior of both the charge conductance and the Seebeck coefficient in very good agreement with available experimental data. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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13 pages, 1267 KiB  
Article
Electron Traversal Times in Disordered Graphene Nanoribbons
by Michael Ridley, Michael A. Sentef and Riku Tuovinen
Entropy 2019, 21(8), 737; https://doi.org/10.3390/e21080737 - 27 Jul 2019
Cited by 9 | Viewed by 3564
Abstract
Using the partition-free time-dependent Landauer–Büttiker formalism for transient current correlations, we study the traversal times taken for electrons to cross graphene nanoribbon (GNR) molecular junctions. We demonstrate electron traversal signatures that vary with disorder and orientation of the GNR. These findings can be [...] Read more.
Using the partition-free time-dependent Landauer–Büttiker formalism for transient current correlations, we study the traversal times taken for electrons to cross graphene nanoribbon (GNR) molecular junctions. We demonstrate electron traversal signatures that vary with disorder and orientation of the GNR. These findings can be related to operational frequencies of GNR-based devices and their consequent rational design. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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35 pages, 1105 KiB  
Article
Generalized Master Equation Approach to Time-Dependent Many-Body Transport
by Valeriu Moldoveanu, Andrei Manolescu and Vidar Gudmundsson
Entropy 2019, 21(8), 731; https://doi.org/10.3390/e21080731 - 25 Jul 2019
Cited by 9 | Viewed by 3548
Abstract
We recall theoretical studies on transient transport through interacting mesoscopic systems. It is shown that a generalized master equation (GME) written and solved in terms of many-body states provides the suitable formal framework to capture both the effects of the Coulomb interaction and [...] Read more.
We recall theoretical studies on transient transport through interacting mesoscopic systems. It is shown that a generalized master equation (GME) written and solved in terms of many-body states provides the suitable formal framework to capture both the effects of the Coulomb interaction and electron–photon coupling due to a surrounding single-mode cavity. We outline the derivation of this equation within the Nakajima–Zwanzig formalism and point out technical problems related to its numerical implementation for more realistic systems which can neither be described by non-interacting two-level models nor by a steady-state Markov–Lindblad equation. We first solve the GME for a lattice model and discuss the dynamics of many-body states in a two-dimensional nanowire, the dynamical onset of the current-current correlations in electrostatically coupled parallel quantum dots and transient thermoelectric properties. Secondly, we rely on a continuous model to get the Rabi oscillations of the photocurrent through a double-dot etched in a nanowire and embedded in a quantum cavity. A many-body Markovian version of the GME for cavity-coupled systems is also presented. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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16 pages, 6065 KiB  
Article
Symmetry Properties of Mixed and Heat Photo-Assisted Noise in the Quantum Hall Regime
by Flavio Ronetti, Matteo Acciai, Dario Ferraro, Jérôme Rech, Thibaut Jonckheere, Thierry Martin and Maura Sassetti
Entropy 2019, 21(8), 730; https://doi.org/10.3390/e21080730 - 25 Jul 2019
Cited by 5 | Viewed by 2648
Abstract
We investigate the photo-assisted charge-heat mixed noise and the heat noise generated by periodic drives in Quantum Hall states belonging to the Laughlin sequence. Fluctuations of the charge and heat currents are due to weak backscattering induced in a quantum point contact geometry [...] Read more.
We investigate the photo-assisted charge-heat mixed noise and the heat noise generated by periodic drives in Quantum Hall states belonging to the Laughlin sequence. Fluctuations of the charge and heat currents are due to weak backscattering induced in a quantum point contact geometry and are evaluated at the lowest order in the tunneling amplitude. Focusing on the cases of a cosine and Lorentzian periodic drive, we show that the different symmetries of the photo-assisted tunneling amplitudes strongly affect the overall profile of these quantities as a function of the AC and DC voltage contributions, which can be tuned independently in experiments. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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15 pages, 11189 KiB  
Article
Current Correlations in a Quantum Dot Ring: A Role of Quantum Interference
by Bogdan R. Bułka and Jakub Łuczak
Entropy 2019, 21(5), 527; https://doi.org/10.3390/e21050527 - 24 May 2019
Cited by 6 | Viewed by 3523
Abstract
We present studies of the electron transport and circular currents induced by the bias voltage and the magnetic flux threading a ring of three quantum dots coupled with two electrodes. Quantum interference of electron waves passing through the states with opposite chirality plays [...] Read more.
We present studies of the electron transport and circular currents induced by the bias voltage and the magnetic flux threading a ring of three quantum dots coupled with two electrodes. Quantum interference of electron waves passing through the states with opposite chirality plays a relevant role in transport, where one can observe Fano resonance with destructive interference. The quantum interference effect is quantitatively described by local bond currents and their correlation functions. Fluctuations of the transport current are characterized by the Lesovik formula for the shot noise, which is a composition of the bond current correlation functions. In the presence of circular currents, the cross-correlation of the bond currents can be very large, but it is negative and compensates for the large positive auto-correlation functions. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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14 pages, 824 KiB  
Article
Quantum Pumping with Adiabatically Modulated Barriers in Three-Band Pseudospin-1 Dirac–Weyl Systems
by Xiaomei Chen and Rui Zhu
Entropy 2019, 21(2), 209; https://doi.org/10.3390/e21020209 - 22 Feb 2019
Cited by 2 | Viewed by 3167
Abstract
In this work, pumped currents of the adiabatically-driven double-barrier structure based on the pseudospin-1 Dirac–Weyl fermions are studied. As a result of the three-band dispersion and hence the unique properties of pseudospin-1 Dirac–Weyl quasiparticles, sharp current-direction reversal is found at certain parameter settings [...] Read more.
In this work, pumped currents of the adiabatically-driven double-barrier structure based on the pseudospin-1 Dirac–Weyl fermions are studied. As a result of the three-band dispersion and hence the unique properties of pseudospin-1 Dirac–Weyl quasiparticles, sharp current-direction reversal is found at certain parameter settings especially at the Dirac point of the band structure, where apexes of the two cones touch at the flat band. Such a behavior can be interpreted consistently by the Berry phase of the scattering matrix and the classical turnstile mechanism. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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Review

Jump to: Editorial, Research

52 pages, 6023 KiB  
Review
Phase-Coherent Dynamics of Quantum Devices with Local Interactions
by Michele Filippone, Arthur Marguerite, Karyn Le Hur, Gwendal Fève and Christophe Mora
Entropy 2020, 22(8), 847; https://doi.org/10.3390/e22080847 - 31 Jul 2020
Cited by 10 | Viewed by 3854
Abstract
This review illustrates how Local Fermi Liquid (LFL) theories describe the strongly correlated and coherent low-energy dynamics of quantum dot devices. This approach consists in an effective elastic scattering theory, accounting exactly for strong correlations. Here, we focus on the mesoscopic capacitor and [...] Read more.
This review illustrates how Local Fermi Liquid (LFL) theories describe the strongly correlated and coherent low-energy dynamics of quantum dot devices. This approach consists in an effective elastic scattering theory, accounting exactly for strong correlations. Here, we focus on the mesoscopic capacitor and recent experiments achieving a Coulomb-induced quantum state transfer. Extending to out-of-equilibrium regimes, aimed at triggered single electron emission, we illustrate how inelastic effects become crucial, requiring approaches beyond LFLs, shedding new light on past experimental data by showing clear interaction effects in the dynamics of mesoscopic capacitors. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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22 pages, 704 KiB  
Review
Entropy Production in Quantum is Different
by Mohammad H. Ansari, Alwin van Steensel and Yuli V. Nazarov
Entropy 2019, 21(9), 854; https://doi.org/10.3390/e21090854 - 31 Aug 2019
Cited by 3 | Viewed by 4118
Abstract
Currently, ‘time’ does not play any essential role in quantum information theory. In this sense, quantum information theory is underdeveloped similarly to how quantum physics was underdeveloped before Erwin Schrödinger introduced his famous equation for the evolution of a quantum wave function. In [...] Read more.
Currently, ‘time’ does not play any essential role in quantum information theory. In this sense, quantum information theory is underdeveloped similarly to how quantum physics was underdeveloped before Erwin Schrödinger introduced his famous equation for the evolution of a quantum wave function. In this review article, we cope with the problem of time for one of the central quantities in quantum information theory: entropy. Recently, a replica trick formalism, the so-called ‘multiple parallel world’ formalism, has been proposed that revolutionizes entropy evaluation for quantum systems. This formalism is one of the first attempts to introduce ‘time’ in quantum information theory. With the total entropy being conserved in a closed system, entropy can flow internally between subsystems; however, we show that this flow is not limited only to physical correlations as the literature suggest. The nonlinear dependence of entropy on the density matrix introduces new types of correlations with no analogue in physical quantities. Evolving a number of replicas simultaneously makes it possible for them to exchange particles between different replicas. We will summarize some of the recent news about entropy in some example quantum devices. Moreover, we take a quick look at a new correspondence that was recently proposed that provides an interesting link between quantum information theory and quantum physics. The mere existence of such a correspondence allows for exploring new physical phenomena as the result of controlling entanglement in a quantum device. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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29 pages, 5268 KiB  
Review
Beyond the State of the Art: Novel Approaches for Thermal and Electrical Transport in Nanoscale Devices
by Robert Biele and Roberto D’Agosta
Entropy 2019, 21(8), 752; https://doi.org/10.3390/e21080752 - 02 Aug 2019
Cited by 6 | Viewed by 3651
Abstract
Almost any interaction between two physical entities can be described through the transfer of either charge, spin, momentum, or energy. Therefore, any theory able to describe these transport phenomena can shed light on a variety of physical, chemical, and biological effects, enriching our [...] Read more.
Almost any interaction between two physical entities can be described through the transfer of either charge, spin, momentum, or energy. Therefore, any theory able to describe these transport phenomena can shed light on a variety of physical, chemical, and biological effects, enriching our understanding of complex, yet fundamental, natural processes, e.g., catalysis or photosynthesis. In this review, we will discuss the standard workhorses for transport in nanoscale devices, namely Boltzmann’s equation and Landauer’s approach. We will emphasize their strengths, but also analyze their limits, proposing theories and models useful to go beyond the state of the art in the investigation of transport in nanoscale devices. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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29 pages, 4850 KiB  
Review
Quantum Phonon Transport in Nanomaterials: Combining Atomistic with Non-Equilibrium Green’s Function Techniques
by Leonardo Medrano Sandonas, Rafael Gutierrez, Alessandro Pecchia, Alexander Croy and Gianaurelio Cuniberti
Entropy 2019, 21(8), 735; https://doi.org/10.3390/e21080735 - 27 Jul 2019
Cited by 13 | Viewed by 5317
Abstract
A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomistic methodologies with quantum transport based approaches. Here, we review our recent work on this [...] Read more.
A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomistic methodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected applications of the PHONON tool to the description of phonon transport in nanostructured materials. The PHONON tool is a module developed as part of the Density-Functional Tight-Binding (DFTB) software platform. We discuss the anisotropic phonon band structure of selected puckered two-dimensional materials, helical and horizontal doping effects in the phonon thermal conductivity of boron nitride-carbon heteronanotubes, phonon filtering in molecular junctions, and a novel computational methodology to investigate time-dependent phonon transport at the atomistic level. These examples illustrate the versatility of our implementation of phonon transport in combination with density functional-based methods to address specific nanoscale functionalities, thus potentially allowing for designing novel thermal devices. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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16 pages, 2741 KiB  
Review
Unusual Quantum Transport Mechanisms in Silicon Nano-Devices
by Giuseppe Carlo Tettamanzi
Entropy 2019, 21(7), 676; https://doi.org/10.3390/e21070676 - 11 Jul 2019
Cited by 2 | Viewed by 4335
Abstract
Silicon-based materials have been the leading platforms for the development of classical information science and are now one of the major contenders for future developments in the field of quantum information science. In this short review paper, while discussing only some examples, I [...] Read more.
Silicon-based materials have been the leading platforms for the development of classical information science and are now one of the major contenders for future developments in the field of quantum information science. In this short review paper, while discussing only some examples, I will describe how silicon Complementary-Metal-Oxide-Semiconductor (CMOS) compatible materials have been able to provide platforms for the observation of some of the most unusual transport phenomena in condensed matter physics. Full article
(This article belongs to the Special Issue Quantum Transport in Mesoscopic Systems)
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