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Special Issue "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: 15 December 2019.

Special Issue Editors

Guest Editor
Dr. David Sánchez

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

Department of Metal and Semiconductor Physics, NTU “Kharkiv Polytechnic Institute”, 61002 Kharkiv, Ukraine
Website | E-Mail
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 papers will be 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 1600 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 (10 papers)

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Research

Jump to: Review

Open AccessArticle
Power, Efficiency and Fluctuations in a Quantum Point Contact as Steady-State Thermoelectric Heat Engine
Entropy 2019, 21(8), 777; https://doi.org/10.3390/e21080777
Received: 11 May 2019 / Revised: 3 July 2019 / Accepted: 29 July 2019 / Published: 8 August 2019
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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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Open AccessArticle
On the Role of Local Many-Body Interactions on the Thermoelectric Properties of Fullerene Junctions
Entropy 2019, 21(8), 754; https://doi.org/10.3390/e21080754
Received: 30 June 2019 / Revised: 23 July 2019 / Accepted: 31 July 2019 / Published: 1 August 2019
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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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Open AccessArticle
Electron Traversal Times in Disordered Graphene Nanoribbons
Entropy 2019, 21(8), 737; https://doi.org/10.3390/e21080737
Received: 28 June 2019 / Revised: 24 July 2019 / Accepted: 25 July 2019 / Published: 27 July 2019
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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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Open AccessArticle
Generalized Master Equation Approach to Time-Dependent Many-Body Transport
Entropy 2019, 21(8), 731; https://doi.org/10.3390/e21080731
Received: 17 June 2019 / Revised: 15 July 2019 / Accepted: 23 July 2019 / Published: 25 July 2019
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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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Open AccessArticle
Symmetry Properties of Mixed and Heat Photo-Assisted Noise in the Quantum Hall Regime
Entropy 2019, 21(8), 730; https://doi.org/10.3390/e21080730
Received: 27 June 2019 / Revised: 22 July 2019 / Accepted: 23 July 2019 / Published: 25 July 2019
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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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Open AccessFeature PaperArticle
Current Correlations in a Quantum Dot Ring: A Role of Quantum Interference
Entropy 2019, 21(5), 527; https://doi.org/10.3390/e21050527
Received: 29 April 2019 / Revised: 17 May 2019 / Accepted: 22 May 2019 / Published: 24 May 2019
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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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Open AccessArticle
Quantum Pumping with Adiabatically Modulated Barriers in Three-Band Pseudospin-1 Dirac–Weyl Systems
Entropy 2019, 21(2), 209; https://doi.org/10.3390/e21020209
Received: 28 November 2018 / Revised: 4 February 2019 / Accepted: 4 February 2019 / Published: 22 February 2019
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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: Research

Open AccessFeature PaperReview
Beyond the State of the Art: Novel Approaches for Thermal and Electrical Transport in Nanoscale Devices
Entropy 2019, 21(8), 752; https://doi.org/10.3390/e21080752
Received: 5 July 2019 / Revised: 28 July 2019 / Accepted: 29 July 2019 / Published: 2 August 2019
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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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Open AccessReview
Quantum Phonon Transport in Nanomaterials: Combining Atomistic with Non-Equilibrium Green’s Function Techniques
Entropy 2019, 21(8), 735; https://doi.org/10.3390/e21080735
Received: 1 July 2019 / Revised: 23 July 2019 / Accepted: 25 July 2019 / Published: 27 July 2019
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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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Open AccessReview
Unusual Quantum Transport Mechanisms in Silicon Nano-Devices
Entropy 2019, 21(7), 676; https://doi.org/10.3390/e21070676
Received: 23 May 2019 / Revised: 25 June 2019 / Accepted: 9 July 2019 / Published: 11 July 2019
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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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