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Electronic Transport In Topological Superconducting Heterostructures
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Book Synopsis Electronic Transport in Topological Superconducting Heterostructures by : Joseph Jude Cuozzo
Download or read book Electronic Transport in Topological Superconducting Heterostructures written by Joseph Jude Cuozzo and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we study Andreev transport and Josephson effects in topological superconducting heterostructures. We study consider two platforms: quantum Hall-superconductor (QH-SC) heterostructures and Josephson junctions. In the first platform, we study QH graphene-SC systems with a focus on the influence symmetry-breaking effects have on Andreev transport. In graphene, valley and spin degeneracy lead to an approximate SU(4) symmetry that is reflected in the approximate 4-fold degeneracy of graphene's Landau levels (LL). We develop an effective low-energy description of Andreev edge states that takes into account the correction to the drift velocity of the QH-SC edge modes due to SU(4) symmetry-breaking effects. We show that Zeeman and valley splitting effects can be used to demonstrate Andreev edge state interference. We also present numerical simulations of Andreev conversion in the lowest LL of canted antiferromagnetic graphene. In the second platform, we analyze Josephson effects and the microwave response of Josephson junctions. We propose a theory for a Leggett collective mode in Dirac semimetals-based Josephson junctions and simulate the microwave response of the junction. We also study Landau-Zener transitions (LZT) between Andreev bound states in Josephson junctions. We present a protocol using superconducting quantum interference devices to differentiate between LZTs between Andreev states, which mimic signatures of Majoranas, and systems with real Majoranas.
Book Synopsis Emergent Transport Properties of Magnetic Topological Insulator Heterostructures by : Kenji Yasuda
Download or read book Emergent Transport Properties of Magnetic Topological Insulator Heterostructures written by Kenji Yasuda and published by Springer Nature. This book was released on 2020-09-07 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reveals unique transport phenomena and functionalities in topological insulators coupled with magnetism and superconductivity. Topological insulators are a recently discovered class of materials that possess a spin-momentum-locked surface state. Their exotic spin texture makes them an exciting platform for investigating emergent phenomena, especially when coupled with magnetism or superconductivity. Focusing on the strong correlation between electricity and magnetism in magnetic topological insulators, the author presents original findings on current-direction-dependent nonreciprocal resistance, current-induced magnetization reversal and chiral edge conduction at the domain wall. In addition, he demonstrates how the coupling between superconductivity and topological surface state leads to substantial nonreciprocal resistance. The author also elucidates the origins of these phenomena and deepens readers’ understanding of the topologically nontrivial electronic state. The book includes several works which are published in top journals and were selected for the President’s Award by the University of Tokyo and for the Ikushi Prize, awarded to distinguished Ph.D. students in Japan.
Book Synopsis Theory of electron transport in superconducting heterostructures by : Magnus Hurd
Download or read book Theory of electron transport in superconducting heterostructures written by Magnus Hurd and published by . This book was released on 1994 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quantum Electronic Transport in Atomically Layered Topological Insulators by : Valla Fatemi
Download or read book Quantum Electronic Transport in Atomically Layered Topological Insulators written by Valla Fatemi and published by . This book was released on 2018 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: The merger of topology and symmetry established a new foundation for understanding the physics of condensed matter, beginning with the notion of topological insulators (TIs) for electronic systems. For the time-reversal invariant TIs, a key aspect is the "helical" mode at the boundary of the system - that is, the ID edge of a 2D topological insulator or the 2D surface of a 3D topological insulator. These helical modes represent the extreme limit of spin-orbit coupling in that the spin-degenercy has been completely lifted while preserving time-reversal symmetry. This property is crucial for proposals realizing exotic excitations like the Majorana bound state. In this thesis, I present a series of experiments investigating electronic transport through the boundary modes of 3D and 2D topological insulators, specifically Bi1.5 Sb0.5 Te1.7 Se1.3 and monolayer WTe 2 , respectively. For the case of ultra-thin WTe 2 , I also present experiments detailing investigations of the 2D bulk states, finding a semimetallic state for the trilayer and a superconducting phase for the monolayer, both of which are strongly tunable by the electric field effect. The discovery of 2D topological insulator and 2D superconductor phases within the same material, accessible by standard solid state elecrostatic gates, places WTe2 in a unique situation among both TIs and superconductors, potentially enabling gate-configurable topological devices within a homogenous material platform.
Book Synopsis Quantum Transport in Topological Insulators by : Johannes Krotz
Download or read book Quantum Transport in Topological Insulators written by Johannes Krotz and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Signatures of Topological Superconductors by : Shu-Ping Lee
Download or read book Signatures of Topological Superconductors written by Shu-Ping Lee and published by . This book was released on 2015 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological superconductors are particularly interesting in light of the active ongoing experimental efforts for realizing exotic physics such as Majorana zero modes. These systems have excitations with non-Abelian exchange statistics, which provides a path towards topological quantum information processing. Intrinsic topological superconductors are quite rare in nature. However, one can engineer topological superconductivity by inducing effective p-wave pairing in materials which can be grown in the laboratory. One possibility is to induce the proximity effect in topological insulators; another is to use hybrid structures of superconductors and semiconductors. The proposal of interfacing s-wave superconductors with quantum spin Hall systems provides a promising route to engineered topological superconductivity. Given the exciting recent progress on the fabrication side, identifying experiments that definitively expose the topological superconducting phase (and clearly distinguish it from a trivial state) raises an increasingly important problem. With this goal in mind, we proposed a detection scheme to get an unambiguous signature of topological superconductivity, even in the presence of ordinarily detrimental effects such as thermal fluctuations and quasiparticle poisoning. We considered a Josephson junction built on top of a quantum spin Hall material. This system allows the proximity effect to turn edge states in effective topological superconductors. Such a setup is promising because experimentalists have demonstrated that supercurrents indeed flow through quantum spin Hall edges. To demonstrate the topological nature of the superconducting quantum spin Hall edges, theorists have proposed examining the periodicity of Josephson currents respect to the phase across a Josephson junction. The periodicity of tunneling currents of ground states in a topological superconductor Josephson junction is double that of a conventional Josephson junction. In practice, this modification of periodicity is extremely difficult to observe because noise sources, such as quasiparticle poisoning, wash out the signature of topological superconductors. For this reason, We propose a new, relatively simple DC measurement that can compellingly reveal topological superconductivity in such quantum spin Hall/superconductor heterostructures. More specifically, We develop a general framework for capturing the junction's current-voltage characteristics as a function of applied magnetic flux. Our analysis reveals sharp signatures of topological superconductivity in the field-dependent critical current. These signatures include the presence of multiple critical currents and a non-vanishing critical current for all magnetic field strengths as a reliable identification scheme for topological superconductivity. This system becomes more interesting as interactions between electrons are involved. By modeling edge states as a Luttinger liquid, we find conductance provides universal signatures to distinguish between normal and topological superconductors. More specifically, we use renormalization group methods to extract universal transport characteristics of superconductor/quantum spin Hall heterostructures where the native edge states serve as a lead. Interestingly, arbitrarily weak interactions induce qualitative changes in the behavior relative to the free-fermion limit, leading to a sharp dichotomy in conductance for the trivial (narrow superconductor) and topological (wide superconductor) cases. Furthermore, we find that strong interactions can in principle induce parafermion excitations at a superconductor/quantum spin Hall junction. As we identify the existence of topological superconductor, we can take a step further. One can use topological superconductor for realizing Majorana modes by breaking time reversal symmetry. An advantage of 2D topological insulator is that networks required for braiding Majoranas along the edge channels can be obtained by adjoining 2D topological insulator to form corner junctions. Physically cutting quantum wells for this purpose, however, presents technical challenges. For this reason, I propose a more accessible means of forming networks that rely on dynamically manipulating the location of edge states inside of a single 2D topological insulator sheet. In particular, I show that edge states can effectively be dragged into the system's interior by gating a region near the edge into a metallic regime and then removing the resulting gapless carriers via proximity-induced superconductivity. This method allows one to construct rather general quasi-1D networks along which Majorana modes can be exchanged by electrostatic means. Apart from 2D topological insulators, Majorana fermions can also be generated in other more accessible materials such as semiconductors. Following up on a suggestion by experimentalist Charlie Marcus, I proposed a novel geometry to create Majorana fermions by placing a 2D electron gas in proximity to an interdigitated superconductor-ferromagnet structure. This architecture evades several manufacturing challenges by allowing single-side fabrication and widening the class of 2D electron gas that may be used, such as the surface states of bulk semiconductors. Furthermore, it naturally allows one to trap and manipulate Majorana fermions through the application of currents. Thus, this structure may lead to the development of a circuit that enables fully electrical manipulation of topologically-protected quantum memory. To reveal these exotic Majorana zero modes, I also proposed an interference scheme to detect Majorana fermions that is broadly applicable to any 2D topological superconductor platform.
Book Synopsis Transport and Subgap States in Superconducting Heterostructures of Effective Dirac Systems by : Jacob Fuchs
Download or read book Transport and Subgap States in Superconducting Heterostructures of Effective Dirac Systems written by Jacob Fuchs and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis deals with superconducting heterostructures of both of the aforementioned materials and examines transport phenomena as well as the formation of subgap states in such systems: In the first chapter, superconducting bilayer graphene with a chemisorbed adatom is investigated and the existence of peculiar subgab states, so-called Yu-Shiba-Rusinov states, is shown. The second chapter deals with T junction devices make out of three-dimensional (3D) TI nanowires. Together with proximity induced superconductivity in one arm and external magnetic fields, this setup allows for the occurence of crossed Andreev reflection, including perfect crossed Andreev reflection, and negative nonlocal conductances. In the third chapter, Josephson junctions of 3D TI nanowires are investigated. The origin of unusual, experimentally observed supercurrent oscillations in dependence of a parallel magnetic field is examinated in a semiclassical analysis.
Book Synopsis Quantum Transport in Topological Materials and Proximity Effect in Ferromagnetic Nanowires by : Jue Jiang
Download or read book Quantum Transport in Topological Materials and Proximity Effect in Ferromagnetic Nanowires written by Jue Jiang and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnetic topological insulator (TI) and the superconductor look different from each other, however, they share a similar electrical transport property of a profound significance: zero resistance. Their potential in the future low-power-consumption applications is beyond measure, therefore, the research attention on TI has been dramatically expanding since its debut in 2009, and the study of superconductivity keeps inspiring people of generations in the past 100 years. The realization of the non-dissipative channel in magnetic TI requires the broken time-reversal-symmetry by ferromagnetic dopants. The engineering of ferromagnetism, in turn, induces new topological phenomena. In this dissertation, we show that by fabricating a magnetic TI/pure TI/magnetic TI sandwich structure, rigorous quantum anomalous Hall (QAH) effect could be realized along with axion insulator state or topological Hall effect, depending on the sample structure. In Cr-doped/non-doped/V-doped TI heterostructures, QAH effect emerges when the magnetizations of the Cr-doped and V-doped magnetic layers are parallel, while an axion insulator state with zero Hall resistance and insulating longitudinal resistance appears when magnetization alignment is anti-parallel; In an Cr-doped/non-doped/Cr-doped TI structure, by tuning the chemical potential, QAH effect crossovers to topological Hall effect, where the electron spins form topologically non-trivial spin textures.Superconductivity, on the other hand, would be destroyed in a ferromagnet due to the decoupling of a Cooper pair by the exchange coupling. Therefore, a spin-singlet Cooper pair is not able to survive in a ferromagnet more than a few nanometers. In this dissertation, however, we show that in a ferromagnetic Ni nanowire (500 nm wide and 40 nm thick), by simply adding a thin Cu buffer layer with natural oxidation between superconducting/ferromagnetic interface, an unusual long-range superconducting proximity effect (up to 136 nm) emerges. Strong evidence points to the Cu oxides for providing a noncollinear magnetic profile that is crucial to the induction of spin-triplet. The spin-triplet pairing can have two electrons with the same spin direction, and thus immune to the exchange coupling of the ferromagnetic nanowire. The experiments of magnetic TI heterostructures and spin-triplet superconductivity presented in this dissertation would inspire more relating studies and pave the way for next-generation energy-efficient spintronic and electronic applications.
Book Synopsis Topological Insulator-superconductor Heterostructures and Devices by : Lin Li
Download or read book Topological Insulator-superconductor Heterostructures and Devices written by Lin Li and published by . This book was released on 2019 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 3D topological insulator has fully gapped insulating bulk state but a conducting surface. Such conducting "surface" states are formed with helical Dirac fermions, with spin-momentum strictly locked by spin-orbital coupling. When coupled to a conventional s-wave superconductor, the surface state behaves just like the desired p-wave superconductor. It has been predicted that Majorana zero-modes obeying non-Abelian statistics can appear in such a system. Braiding operations on the Majorana zero-modes can realize topological quantum computing that is innately error-tolerant. Therefore, it has boosted extensive interest in the topological insulator-superconductor (TI-S) heterostructures. High quality TI-S heterostructures on wafer size scale is demanded for both fundamental studies as well as applications in the future. The study in this thesis explored molecular beam epitaxy (MBE) growth of TI-S bilayer heterostructures by depositing 3D topological insulator (Bi1-xSbx)2Te3 (BST) on superconductors including Nb and MgB2. The BST-Nb heterostructure has been demonstrated to have high crystalline quality and clear interface. BST-MgB2 heterostructure suffers from chemical reaction happening at its interface, which can be inhibited by lowering growth temperature and prevented by inserting a thin layer of Nb in between to form BST-Nb/MgB2 structure. In addition, by depositing a top layer of Nb on the bilayer heterostructures and proceeding to fabrication, we achieved vertical S-TI-S junctions that have seldomly been studied. Josephson coupling between the two superconducting electrodes and between proximity induced superconducting TI surfaces was observed on the Nb-BST-Nb and Nb-BST-Nb/MgB2 junctions, giving two different critical current transitions on the I-V characteristics. In the Nb-BST-MgB2 junction, tunneling effect through normal electrons was dominating without Josephson current being observed, which is due to an insulating layer formed at the BST-MgB2 interface. Despite the difference in overall conductance features, a zero bias conductance peak (ZBCP) was observed on the dI/dV-V curves from all three kinds of junction. The origin of this ZBCP was discussed. The thin film heterostructures obtained in this project can be good platforms to search for Majorana zero-modes through various approaches. We have also demonstrated the heterostructures are compatible with fabrication processes by patterning vertical junctions. Transport measurement results on these junctions could provide some insight into understanding the physical processes happening at the TI-S interfaces.
Book Synopsis A Transport and Optical Study on Topological Semimetals and 2D Materials by : Wenkai Zheng
Download or read book A Transport and Optical Study on Topological Semimetals and 2D Materials written by Wenkai Zheng and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is mainly focus on the 3D topological semimetal and 2D materials. If you ask a physicist to name the most significant discovery in solid-state physics over the recent 50 years, and highly likely, if not high-temperature superconductivity, will be topological materials or 2D materials. The study of them has profoundly impacted our understanding of the solid-state system, as recognized by four Nobel prizes. Chapter 1 is a brief introduction of topological semimetal and 2D materials. Chapter 2 focuses on a quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe2 and PtTe2. In high-quality single crystals of both compounds, id est displaying carrier mobilities between 10^3 and 10^4 cm2/Vs, we observed a large non-saturating magnetoresistivity (MR) which in PtTe2 at a temperature T = 1.3 K, leads to an increase in the resistivity up to 5*10^4% under a magnetic field [mu]0H = 62 T. These high mobilities correlate with their light effective masses in the range of 0.04 to 1 bare electron mass according to our measurements. For PdTe2 the experimentally determined Fermi surface cross-sectional areas show an excellent agreement with those resulting from band-structure calculations. Surprisingly, this is not the case for PtTe2 whose agreement between calculations and experiments is relatively poor even when electronic correlations are included in the calculations. Therefore, our study provides a strong support for the existence of a Dirac type-II node in PdTe2 and probably also for PtTe2. Band structure calculations indicate that the topologically non-trivial bands of PtTe2 do not cross the Fermi-level ([epsilon]F). In contrast, for PdTe2 the Dirac type-II cone does intersect [epsilon]F , although our calculations also indicate that the associated cyclotron orbit on the Fermi surface is located in a distinct kz plane with respect to the one of the Dirac type-II node. Therefore it should yield a trivial Berry-phase. Chapter 3 presents a study on the Fermi-surface of the Dirac type-II semi-metallic candidate NiTe2. In contrast to its isostructural compounds like PtSe2, band structure calculations predict NiTe2 to display a tilted Dirac node very close to its Fermi level that is located along the [gamma] to A high symmetry direction within its first Brillouin zone (FBZ). The angular dependence of the dHvA frequencies is found to be in agreement with the first-principle calculations when the electronicbands are slightly shifted with respect to the Fermi level ([epsilon]F ), and therefore provide support for the existence of a Dirac type-II node in NiTe2. Nevertheless, we observed mild disagreements between experimental observations and density Functional theory calculations as, for example, nearly isotropic and light experimental effective masses. This indicates that the dispersion of the bands is not well captured by DFT. Despite the coexistence of Dirac-like fermions with topologically trivial carriers, samples of the highest quality display an anomalous and large, either linear or sublinear magnetoresistivity. This suggests that Lorentz invariance breaking Dirac-like quasiparticles dominate the carrier transport in this compound. Chapter 4 describes a study on a 2D superconductor. The superconducting [alpha]-phase thin molybdenum carbide flakes were first synthesized, and a subsequent sulfurization treatment induced the formation of vertical heterolayer systems consisting of different phases of molybdenum carbide- ranging from [alpha] to [gamma]' and [gamma] phases-in conjunction with molybdenum sulfide layers. These transition-metal carbide/disulfide heterostructures exhibited critical superconducting temperatures as high as 6 K, higher than that of the starting single-phased [alpha]-Mo2C (4 K). We analyzed possible interface configurations to explain the observed moire patterns resulting from the vertical heterostacks. Our density-functional theory (DFT) calculations indicate that epitaxial strain and moire patterns lead to a higher interfacial density of states, which favors superconductivity. Suchengineered heterostructures might allow the coupling of superconductivity to the topologically nontrivial surface states featured by transition-metal carbide phases composing these heterostructures potentially leading to unconventional superconductivity. Moreover, we envisage that our approach could also be generalized to other metal carbide and nitride systems that could exhibit high-temperature superconductivity. In chapter 5, We introduce a new moire system: InSe/GaSe hetero-structure. To date, the moire physics has been constrained mainly by two factors i) the dimensionality, defined by the stacking of monolayers, and ii) the twist angle [phi] which unveils novel phases only at quite precise values (e.g. superconductivity, orbital magnetism, correlated insulator states). Here, we overcome these practical limitations through a new class of heterostructures composed of strongly coupled layers of [gamma]-InSe on [epsilon]-GaSe revealing compelling evidence for the moire potential even in thick stacked layers and at arbitrary values of [phi]. We detect a pronounced interlayer exciton (Xi) of very small radius according to the Stark effect, that is composed of several superimposed emissions uniformly spaced in energy [delta]E displaying a pronounced [phi]-dependence. In the interfacial area, similar behavior is also shown by the intralayer exciton of GaSe (X0(Ga)). The strong correlation between [phi] and [delta]Eimplies localization of excitations at the moire potential minima. In contrast to transition metal dichalcogenides (TMDs), the moire potential modulates the multi-component Xi over the entire range of [phi] due to their direct band-gap at the center of the Brillouin zone. Therefore, [gamma]-InSe/[epsilon]-GaSe interfaces offer an unprecedented level of moire exciton tunability not yet achieved in other vans der Waals heterostructures. Our results unveil clear pathways for quantum optoelectronics while offering opportunities to study electronic correlations over a broad range of moire periodicities and layer thicknesses.
Book Synopsis Exploring the Three-dimensional Quantum Anomalous Hall Effect and Topological Superconductivity in Topological Insulator Heterostructures by : Ruoxi Zhang
Download or read book Exploring the Three-dimensional Quantum Anomalous Hall Effect and Topological Superconductivity in Topological Insulator Heterostructures written by Ruoxi Zhang and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological materials exhibit unique properties that make them robust against local defects and perturbations. These properties stem from the distinctive band structure compared to conventional materials, which are characterized by different topological invariants. In this thesis, we study two phenomena that arise in epitaxial topological insulator (TIs) films/heterostructures. The first phenomenon is the quantum anomalous Hall (QAH) effect. The QAH effect requires no external magnetic field and possesses non-dissipative chiral edge states that are resistant to local disorders. The second phenomenon is the topological superconducting (TSC) states. The TSC state hosts quasiparticle excitations, including Majorana zero modes (MZMs) and chiral Majorana edge modes (CMEMs). These excitations have potential applications in fault-tolerant topological quantum computations. The first experimental observation of the QAH effect was realized in molecular beam epitaxy (MBE)-grown magnetically doped TI thin films, which offer the advantages of scalability and reproducibility. However, the introduction of magnetic dopants also leads to higher disorder density in TI thin films. To overcome this limitation, we employed MBE-grown magnetically doped TI/TI/magnetically doped TI sandwich heterostructures to separate the magnetic dopants from the TI bulk. By employing this method, we successfully realized high Chern number QAH states, Chern domain walls, and hundred-nanometer-thick QAH samples. These results reveal new phases of matter and the underlying physics of the QAH phase transition induced by interlayer coupling. The second half of the thesis describes our effort in the TSC state in QAH insulators and TIs with induced superconductivity. The first project in this effort focuses on the search for CMEMs, which are predicted to emerge in QAH/superconductor hybrid structures. We examined a prior transport experiment that claimed the realization of CMEMs by measuring the two-terminal resistance. We improved the experimental design by fabricating Josephson junction and tunneling junction devices based on Bi2Te3 and (Bi,Sb)2Te3, and obtained transport results that suggest the dominance of Dirac surface states in vortex generation in the junction area.
Book Synopsis Andreev Reflection in Superconducting Junctions by : Yasuhiro Asano
Download or read book Andreev Reflection in Superconducting Junctions written by Yasuhiro Asano and published by Springer Nature. This book was released on 2021-11-12 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a primer on the fundamental theory of Andreev reflection, a fundamental process in the motion of a Cooper pair, which dominates low-energy electronic transport properties in superconductor junctions including differential conductance and Josephson current. The book concisely describes how Andreev reflection impacts the low-energy physics of electronic transport especially in topologically non-trivial superconductor junctions. In addition, it includes an introduction to topological superconductors, covering topological classification, chiral and helical superconductors, and topological edges. The book is based on the author’s lecture notes, used in his intensive lectures and while supervising his upper undergraduate and early graduate students. To fully benefit from this concise primer, readers only need an undergraduate background in quantum mechanics and statistical mechanics. Further, by highlighting Josephson junctions of topological superconductors, the book offers readers a glimpse into cutting-edge topics.
Book Synopsis Quantum Transport in Mesoscopic Systems by : David Sánchez
Download or read book Quantum Transport in Mesoscopic Systems written by David Sánchez and published by MDPI. This book was released on 2021-01-06 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mesoscopic physics deals with systems larger than single atoms but small enough to retain their quantum properties. The possibility to create and manipulate conductors of the nanometer scale has given birth to a set of phenomena that have revolutionized physics: quantum Hall effects, persistent currents, weak localization, Coulomb blockade, etc. This Special Issue tackles the latest developments in the field. Contributors discuss time-dependent transport, quantum pumping, nanoscale heat engines and motors, molecular junctions, electron–electron correlations in confined systems, quantum thermo-electrics and current fluctuations. The works included herein represent an up-to-date account of exciting research with a broad impact in both fundamental and applied topics.
Book Synopsis Semiconductor Nanodevices by : David Ritchie
Download or read book Semiconductor Nanodevices written by David Ritchie and published by Elsevier. This book was released on 2021-10-24 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor Nanodevices: Physics, Technology and Applications explores recent advances in the field. The behaviour of these devices is controlled by regions of nanoscale dimensions which typically determine the local density of electronic states and lead to the observation of a range of quantum effects with significant potential for exploitation. The book opens with an introduction describing the development of this research field over the past few decades which contrasts quantum-controlled devices to conventional nanoscale electronic devices where an emphasis has often been placed on minimising quantum effects. This introduction is followed by seven chapters describing electrical nanodevices and five chapters describing opto-electronic nanodevices; individual chapters review important recent advances. These chapters include specific fabrication details for the structures and devices described as well as a discussion of the physics made accessible. It is an important reference source for physicists, materials scientists and engineers who want to learn more about how semiconductor-based nanodevices are being developed for both science and potential industrial applications. The section on electrical devices includes chapters describing the study of electron correlation effects using transport in quantum point contacts and tunnelling between one-dimensional wires; the high-frequency pumping of single electrons; thermal effects in quantum dots; the use of silicon quantum dot devices for qubits and quantum computing; transport in topological insulator nanoribbons and a comprehensive discussion of noise in electrical nanodevices. The optical device section describes the use of self-assembled III-V semiconductor nanostructures embedded in devices for a range of applications, including quantum dots for single and entangled photon sources, quantum dots and nanowires in lasers and quantum dots in solar cells. Explores the major industrial applications of semiconductor nanodevices Explains fabrication techniques for the production of semiconductor nanodevices Assesses the challenges for the mass production of semiconductor nanodevices
Book Synopsis Quantized Phenomena of Transport and Magneto-Optics in Magnetic Topological Insulator Heterostructures by : Masataka Mogi
Download or read book Quantized Phenomena of Transport and Magneto-Optics in Magnetic Topological Insulator Heterostructures written by Masataka Mogi and published by Springer Nature. This book was released on 2022-05-07 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents experimental studies on emergent transport and magneto-optical properties in three-dimensional topological insulators with two-dimensional Dirac fermions on their surfaces. Designing magnetic heterostructures utilizing a cutting-edge growth technique (molecular beam epitaxy) stabilizes and manifests new quantization phenomena, as confirmed by low-temperature electrical transport and time-domain terahertz magneto-optical measurements. Starting with a review of the theoretical background and recent experimental advances in topological insulators in terms of a novel magneto-electric coupling, the author subsequently explores their magnetic quantum properties and reveals topological phase transitions between quantum anomalous Hall insulator and trivial insulator phases; a new topological phase (the axion insulator); and a half-integer quantum Hall state associated with the quantum parity anomaly. Furthermore, the author shows how these quantum phases can be significantly stabilized via magnetic modulation doping and proximity coupling with a normal ferromagnetic insulator. These findings provide a basis for future technologies such as ultra-low energy consumption electronic devices and fault-tolerant topological quantum computers.
Book Synopsis Electronic Transport in Topological Insulator Nanostructures by : Seung Sae Hong
Download or read book Electronic Transport in Topological Insulator Nanostructures written by Seung Sae Hong and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological insulators are states of quantum matter with an insulating gap in the bulk and gapless surface states. The exotic spin nature of the surface electrons, resulting in topological protection from localization, suggests unconventional applications in electronics as well as fundamental scientific interests. While these exotic states have been investigated via surface-sensitive techniques intensively, electronic transport device, crucial to realize topological electronics, has lagged behind due to material challenges in candidate materials. Topological insulator nanostructure is an attractive candidate for device applications, as the size effect and boundary conditions offer a unique way to enhance / tailor the surface electron transport. In this dissertation, we first describe the design principle of topological insulator nanomaterials, with an emphasis on bismuth selenide. Two major material challenges, dominant bulk electron contribution and low surface mobility due to surface oxidation, are discussed and the solutions via nanomaterial synthesis are achieved. Elemental doping and core-shell heterostructures are developed to suppress bulk carriers and to achieve high surface electron mobility. The high electronic mobility allows us to observe Shubnikov-de Haas oscillations originated from the surface Dirac fermions. In addition to the material development, we also investigate transport properties from helical nature of the surface electrons. 1D modes of surface electrons in bismuth selenide nanowire Aharonov-Bohm interferometers is a unique electronic state providing an opportunity to reveal helical spin nature and topological protection via transport. The helical 1D mode, directly observed near the Dirac point under half magnetic flux quantum, is robust against disorder but fragile against a magnetic field breaking time-reversal-symmetry. The newly discovered 1D helical mode is expected to open a new direction to study topological electronics, as well as future applications.
Book Synopsis Andreev Reflection in Superconducting Junctions by : Yasuhiro Asano
Download or read book Andreev Reflection in Superconducting Junctions written by Yasuhiro Asano and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a primer on the fundamental theory of Andreev reflection, a fundamental process in the motion of a Cooper pair, which dominates low-energy electronic transport properties in superconductor junctions including differential conductance and Josephson current. The book concisely describes how Andreev reflection impacts the low-energy physics of electronic transport especially in topologically non-trivial superconductor junctions. In addition, it includes an introduction to topological superconductors, covering topological classification, chiral and helical superconductors, and topological edges. The book is based on the author's lecture notes, used in his intensive lectures and while supervising his upper undergraduate and early graduate students. To fully benefit from this concise primer, readers only need an undergraduate background in quantum mechanics and statistical mechanics. Further, by highlighting Josephson junctions of topological superconductors, the book offers readers a glimpse into cutting-edge topics.
