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Lozano MS, Gómez VJ. Epitaxial growth of crystal phase quantum dots in III-V semiconductor nanowires. NANOSCALE ADVANCES 2023; 5:1890-1909. [PMID: 36998660 PMCID: PMC10044505 DOI: 10.1039/d2na00956k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 03/06/2023] [Indexed: 06/19/2023]
Abstract
Crystal phase quantum dots (QDs) are formed during the axial growth of III-V semiconductor nanowires (NWs) by stacking different crystal phases of the same material. In III-V semiconductor NWs, both zinc blende (ZB) and wurtzite (WZ) crystal phases can coexist. The band structure difference between both crystal phases can lead to quantum confinement. Thanks to the precise control in III-V semiconductor NW growth conditions and the deep knowledge on the epitaxial growth mechanisms, it is nowadays possible to control, down to the atomic level, the switching between crystal phases in NWs forming the so-called crystal phase NW-based QDs (NWQDs). The shape and size of the NW bridge the gap between QDs and the macroscopic world. This review is focused on crystal phase NWQDs based on III-V NWs obtained by the bottom-up vapor-liquid-solid (VLS) method and their optical and electronic properties. Crystal phase switching can be achieved in the axial direction. In contrast, in the core/shell growth, the difference in surface energies between different polytypes can enable selective shell growth. One reason for the very intense research in this field is motivated by their excellent optical and electronic properties both appealing for applications in nanophotonics and quantum technologies.
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Affiliation(s)
- Miguel Sinusia Lozano
- Nanophotonics Technology Center, Universitat Politècnica de València, Camino de Vera s/n Building 8F, 2a Floor 46022 Valencia Spain
| | - Víctor J Gómez
- Nanophotonics Technology Center, Universitat Politècnica de València, Camino de Vera s/n Building 8F, 2a Floor 46022 Valencia Spain
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2
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Preparation of Polyphenylene Ring Derivative Dyes with Wide Wave Absorption Properties and Their Performance Study. Molecules 2022; 27:molecules27175551. [PMID: 36080315 PMCID: PMC9458254 DOI: 10.3390/molecules27175551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 08/22/2022] [Accepted: 08/24/2022] [Indexed: 11/17/2022] Open
Abstract
Some conjugated benzene ring molecules were prepared using the Sonogashira reaction, and the molecules were post-functionally modified using click chemistry. The optical and electrical band gaps were measured using UV-VIS absorption spectroscopy and the three-electrode method, and the results of both were verified against each other to prove the accuracy of the characterization. In addition, the optical performances of the material were studied by z-scan; almost all materials exhibited good nonlinear optical properties and interconversion between saturable and anti-saturable absorption due to the invocation of click reagents.
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3
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Optical Properties of New Third-Order Nonlinear Materials Modified by Click Chemistry. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27155006. [PMID: 35956956 PMCID: PMC9370522 DOI: 10.3390/molecules27155006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/20/2022] [Accepted: 08/03/2022] [Indexed: 11/23/2022]
Abstract
A high-yielding click reaction was used to synthesize a series of highly conjugated, symmetrical, as well as asymmetrical compounds with a benzene core. Cyclic voltammetry and ultraviolet/visible absorption spectroscopy were carried out, and proved that the side groups of the benzene derivatives played an important role in the energy gaps, and affected the third-order non-linear optical response. The maximum absorption wavelength of the series of benzene derivatives showed an obvious red-shift. Moreover, the addition of resilient electron-withdrawing groups significantly narrowed the energy levels as compared with precursors. The third-order nonlinear properties of this benzene derivative were tested by the Z-scan technique. The expected properties of this series of molecules were obtained, and it was found that the series of molecules undergoes a transition from reverse saturable absorption to saturable absorption, which has certain reference significance for a nonlinear optical field.
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4
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Zhao Y, Liu X, Zhao X, Li Q, Zhao Y, Guo Z, He Z, Zhang H, Gao J, Miao Z. Preparation of symmetrical and asymmetrical multi-phenylene ring nonlinear optical materials with click chemical modifications and their properties. Tetrahedron 2022. [DOI: 10.1016/j.tet.2022.132992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Debbarma R, Potts H, Stenberg CJ, Tsintzis A, Lehmann S, Dick K, Leijnse M, Thelander C. Effects of Parity and Symmetry on the Aharonov-Bohm Phase of a Quantum Ring. NANO LETTERS 2022; 22:334-339. [PMID: 34910870 PMCID: PMC8759086 DOI: 10.1021/acs.nanolett.1c03882] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/03/2021] [Indexed: 06/14/2023]
Abstract
We experimentally investigate the properties of one-dimensional quantum rings that form near the surface of nanowire quantum dots. In agreement with theoretical predictions, we observe the appearance of forbidden gaps in the evolution of states in a magnetic field as the symmetry of a quantum ring is reduced. For a twofold symmetry, our experiments confirm that orbital states are grouped pairwise. Here, a π-phase shift can be introduced in the Aharonov-Bohm relation by controlling the relative orbital parity using an electric field. Studying rings with higher symmetry, we note exceptionally large orbital contributions to the effective g-factor (up to 300), which are many times higher than those previously reported. These findings show that the properties of a phase-coherent system can be significantly altered by the nanostructure symmetry and its interplay with wave function parity.
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Affiliation(s)
- Rousan Debbarma
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Heidi Potts
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Calle Janlén Stenberg
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Athanasios Tsintzis
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Sebastian Lehmann
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Kimberly Dick
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Martin Leijnse
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Claes Thelander
- Division
of Solid State Physics and NanoLund and Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
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6
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Potts H, Chen IJ, Tsintzis A, Nilsson M, Lehmann S, Dick KA, Leijnse M, Thelander C. Electrical control of spins and giant g-factors in ring-like coupled quantum dots. Nat Commun 2019; 10:5740. [PMID: 31844044 PMCID: PMC6915759 DOI: 10.1038/s41467-019-13583-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 11/11/2019] [Indexed: 11/09/2022] Open
Abstract
Emerging theoretical concepts for quantum technologies have driven a continuous search for structures where a quantum state, such as spin, can be manipulated efficiently. Central to many concepts is the ability to control a system by electric and magnetic fields, relying on strong spin-orbit interaction and a large g-factor. Here, we present a mechanism for spin and orbital manipulation using small electric and magnetic fields. By hybridizing specific quantum dot states at two points inside InAs nanowires, nearly perfect quantum rings form. Large and highly anisotropic effective g-factors are observed, explained by a strong orbital contribution. Importantly, we find that the orbital contributions can be efficiently quenched by simply detuning the individual quantum dot levels with an electric field. In this way, we demonstrate not only control of the effective g-factor from 80 to almost 0 for the same charge state, but also electrostatic change of the ground state spin.
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Affiliation(s)
- H Potts
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden.
| | - I-J Chen
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - A Tsintzis
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - M Nilsson
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - S Lehmann
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - K A Dick
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
- Centre for Analysis and Synthesis, Lund University, SE-221 00, Lund, Sweden
| | - M Leijnse
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - C Thelander
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden.
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7
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Nilsson M, Boström FV, Lehmann S, Dick KA, Leijnse M, Thelander C. Tuning the Two-Electron Hybridization and Spin States in Parallel-Coupled InAs Quantum Dots. PHYSICAL REVIEW LETTERS 2018; 121:156802. [PMID: 30362807 DOI: 10.1103/physrevlett.121.156802] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Indexed: 05/27/2023]
Abstract
We study spin transport in the one- and two-electron regimes of parallel-coupled double quantum dots (DQDs). The DQDs are formed in InAs nanowires by a combination of crystal-phase engineering and electrostatic gating, with an interdot tunnel coupling (t) tunable by one order of magnitude. Large single-particle energy separations (up to 10 meV) and |g^{*}| factors (∼10) enable detailed studies of the B-field-induced transition from a singlet-to-triplet ground state as a function of t. In particular, we investigate how the magnitude of the spin-orbit-induced singlet-triplet anticrossing depends on t. For cases of strong coupling, we find values of 230 μeV for the anticrossing using excited-state spectroscopy. Experimental results are reproduced by calculations based on rate equations and a DQD model including a single orbital in each dot.
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Affiliation(s)
- Malin Nilsson
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Florinda Viñas Boström
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Sebastian Lehmann
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Kimberly A Dick
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
- Center for Analysis and Synthesis, Lund University, Box 124, S-221 00 Lund, Sweden
| | - Martin Leijnse
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Claes Thelander
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
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8
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Gong H, Ullah A, Ye L, Zheng X, Yan Y. Quantum entanglement of parallel-coupled double quantum dots: A theoretical study using the hierarchical equations of motion approach. CHINESE J CHEM PHYS 2018. [DOI: 10.1063/1674-0068/31/cjcp1806138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Hong Gong
- Hefei National Laboratory for Physical Sciences at the Microscale & Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Arif Ullah
- Hefei National Laboratory for Physical Sciences at the Microscale & Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - LvZhou Ye
- Hefei National Laboratory for Physical Sciences at the Microscale & Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiao Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale & Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - YiJing Yan
- Hefei National Laboratory for Physical Sciences at the Microscale & iChEM, University of Science and Technology of China, Hefei 230026, China
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9
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Nicolí G, Ferguson MS, Rössler C, Wolfertz A, Blatter G, Ihn T, Ensslin K, Reichl C, Wegscheider W, Zilberberg O. Cavity-Mediated Coherent Coupling between Distant Quantum Dots. PHYSICAL REVIEW LETTERS 2018; 120:236801. [PMID: 29932683 DOI: 10.1103/physrevlett.120.236801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Indexed: 06/08/2023]
Abstract
Scalable architectures for quantum information technologies require one to selectively couple long-distance qubits while suppressing environmental noise and cross talk. In semiconductor materials, the coherent coupling of a single spin on a quantum dot to a cavity hosting fermionic modes offers a new solution to this technological challenge. Here, we demonstrate coherent coupling between two spatially separated quantum dots using an electronic cavity design that takes advantage of whispering-gallery modes in a two-dimensional electron gas. The cavity-mediated, long-distance coupling effectively minimizes undesirable direct cross talk between the dots and defines a scalable architecture for all-electronic semiconductor-based quantum information processing.
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Affiliation(s)
- Giorgio Nicolí
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Clemens Rössler
- Infineon Technologies Austria, Siemensstraße 2, 9500 Villach, Austria
| | | | - Gianni Blatter
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Christian Reichl
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Oded Zilberberg
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
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10
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Nilsson M, Chen IJ, Lehmann S, Maulerova V, Dick KA, Thelander C. Parallel-Coupled Quantum Dots in InAs Nanowires. NANO LETTERS 2017; 17:7847-7852. [PMID: 29172541 DOI: 10.1021/acs.nanolett.7b04090] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We use crystal-phase tuning during epitaxial growth of InAs nanowires to create quantum dots with very strong confinement. A set of gate electrodes are used to reproducibly split the quantum dots into even smaller pairs for which we can control the populations down to the last electron. The double quantum dots, which are parallel-coupled to source and drain, show clear and stable odd-even level pairing due to spin degeneracy and the strong confinement. The combination of hard-wall barriers to source and drain, shallow interdot tunnel barriers, and very high single-particle excitation energies allow an order of magnitude tuning of the strength for the first intramolecular bond. We show examples for nanowires with different facet orientations, and suggest possible mechanisms behind the reproducible double-dot formation.
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Affiliation(s)
- Malin Nilsson
- Division of Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - I-Ju Chen
- Division of Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Sebastian Lehmann
- Division of Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Vendula Maulerova
- Division of Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Kimberly A Dick
- Division of Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Claes Thelander
- Division of Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
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11
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Shakouri K, Esmaeilzadeh M, Szafran B, Salehani HK. Electronic properties of a defected ring-shaped quantum dot array. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:225801. [PMID: 21572222 DOI: 10.1088/0953-8984/23/22/225801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this paper we present a theoretical study of an array of circularly arranged quantum dots with a rectangular Kronig-Penney potential in the presence of a perpendicular magnetic field. For a perfect array of dots, an analytical formula for energy dispersion is derived. We also study the effects of disorder on the energy spectrum and persistent tunneling current. The effects of electron-electron interaction are then investigated for both perfect and defected arrays. We show that the period of Aharonov-Bohm oscillations is fractional for interacting electrons confined in a perfect array. In contrast, for a defected array, we find a critical value of electron-electron interaction strength at which a transition occurs from an integer to a fractional period of Aharonov-Bohm oscillations. Moreover, it is shown that the persistent current of weakly interacting electrons confined in a defected array is greater than the current of non- or strongly interacting electrons.
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Affiliation(s)
- Kh Shakouri
- Department of Physics, Iran University of Science and Technology, Narmak, Tehran, Iran
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12
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Wang WZ. Spin filtering and quantum phase transition in double quantum dots attached to spin-polarized leads. NANOTECHNOLOGY 2011; 22:205203. [PMID: 21444959 DOI: 10.1088/0957-4484/22/20/205203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We study the spin filtering and quantum phase transition (QPT) in double quantum dots attached to spin-polarized leads. For spin-independent leads, we observe a Kosterlitz-Thouless transition between the local triplet and doublet. For spin-polarized leads, the above QPT becomes first order, and Kondo splitting, gate-controlled spin reversal and a perfect spin filtering are observed. The breaking of spin-rotation SU(2) symmetry and the interdot transport mediated by the conduction electron are responsible for the fully spin-polarized conductance. Because spin-polarized leads suppress the Kondo effect, in order to obtain a large conductance with perfect spin filtering, one should choose leads with small spin polarization, such as Rashba spin-orbital coupling leads.
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Affiliation(s)
- Wei-zhong Wang
- Department of Physics, Wuhan University, Wuhan, People's Republic of China.
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13
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Hatano T, Kubo T, Tokura Y, Amaha S, Teraoka S, Tarucha S. Aharonov-Bohm oscillations changed by indirect interdot tunneling via electrodes in parallel-coupled vertical double quantum dots. PHYSICAL REVIEW LETTERS 2011; 106:076801. [PMID: 21405529 DOI: 10.1103/physrevlett.106.076801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 09/14/2010] [Indexed: 05/30/2023]
Abstract
Aharonov-Bohm (AB) oscillations are studied for a parallel-coupled vertical double quantum dot with a common source and drain electrode. We observe AB oscillations of current via a one-electron bonding state as the ground state and an antibonding state as the excited state. As the center gate voltage becomes more negative, the oscillation period is clearly halved for both the bonding and antibonding states, and the phase changes by half a period for the antibonding state. This result can be explained by a calculation that takes account of the indirect interdot coupling via the two electrodes.
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Affiliation(s)
- T Hatano
- JST, ICORP, Quantum Spin Information Project, Atsugi-shi, Kanagawa, Japan
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14
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Kwaśniowski A, Adamowski J. Tuning the exchange interaction by an electric field in laterally coupled quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:235601. [PMID: 21825588 DOI: 10.1088/0953-8984/21/23/235601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The effect of an external electric field on the exchange interaction has been studied by an exact diagonalization method for two electrons in laterally coupled quantum dots (QDs). We have performed a systematic study of several nanodevices that contain two gate-defined QDs with different shapes and sizes located between source and drain contacts. The confinement potential is modeled by two potential wells with a variable range and softness. In all the considered nanodevices, the overall dependence of exchange energy J on electric field F is similar, i.e. for low fields J increases with increasing F, while for intermediate fields J reaches a maximum and then abruptly falls to zero if F exceeds a certain critical value. However, the J(F) dependence also shows certain characteristic properties that depend on the nanodevice geometry. We have found that the low- and intermediate-field behavior can be accurately parameterized by a linear function J(F) = αF+β, where α is independent of the nanodevice geometry and softness of the confinement potential. We have shown that the linear J(F) relation appears only if the tunnel coupling between the QDs is weak, i.e. the interdot separation is sufficiently large. This relation becomes nonlinear for the strong interdot coupling. For specific nanodevices we have found that the J(F) dependence exhibits a plateau in a broad electric-field regime. The properties of the exchange energy found in the present paper can be applied to all electrical manipulation of electron spin qubits.
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Affiliation(s)
- A Kwaśniowski
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059 Kraków, Poland
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15
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Kodera T, Ono K, Kitamura Y, Tokura Y, Arakawa Y, Tarucha S. Quantitative estimation of exchange interaction energy using two-electron vertical double quantum dots. PHYSICAL REVIEW LETTERS 2009; 102:146802. [PMID: 19392466 DOI: 10.1103/physrevlett.102.146802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Indexed: 05/27/2023]
Abstract
We use Pauli-spin blockade in two-electron vertical double quantum dots to quantitatively estimate the exchange energy J in a wide range of interdot level detuning Delta and fully compare it with calculations. Pauli-spin blockade is lifted via a singlet- (S-)triplet (T) transition mediated by hyperfine coupling, which abruptly occurs in our devices when the S-T transition energy or J is compensated by the Zeeman energy. We use this feature to derive J depending on Delta between the S-S and T-T resonances. The obtained J versus Delta including the resonance effect is perfectly reproduced by Hubbard model calculations.
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Affiliation(s)
- T Kodera
- Institute for Nano Quantum Information Electronics, the University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
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16
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Stopa M, Marcus CM. Magnetic field control of exchange and noise immunity in double quantum dots. NANO LETTERS 2008; 8:1778-1782. [PMID: 18494532 DOI: 10.1021/nl801282t] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We employ density functional calculated eigenstates as a basis for exact diagonalization studies of semiconductor double quantum dots, with two electrons, through the transition from the symmetric bias regime to the regime where both electrons occupy the same dot. We calculate the singlet-triplet splitting J(epsilon) as a function of bias detuning epsilon and explain its functional shape with a simple, double anticrossing model. A voltage noise suppression "sweet spot," where d J(epsilon)/d(epsilon) = 0 with nonzero J(epsilon), is predicted and shown to be tunable with a magnetic field B.
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Affiliation(s)
- M Stopa
- Center for Nanoscale Systems, and Department of Physics, Harvard University, Cambridge, MA 02138, USA.
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17
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Yannouleas C, Landman U. Symmetry breaking and quantum correlations in finite systems: studies of quantum dots and ultracold Bose gases and related nuclear and chemical methods. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2007; 70:2067-2148. [PMID: 34996294 DOI: 10.1088/0034-4885/70/12/r02] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Indexed: 06/14/2023]
Abstract
Investigations of emergent symmetry breaking phenomena occurring in small finite-size systems are reviewed, with a focus on the strongly correlated regime of electrons in two-dimensional semiconductor quantum dots and trapped ultracold bosonic atoms in harmonic traps. Throughout the review we emphasize universal aspects and similarities of symmetry breaking found in these systems, as well as in more traditional fields like nuclear physics and quantum chemistry, which are characterized by very different interparticle forces. A unified description of strongly correlated phenomena in finite systems of repelling particles (whether fermions or bosons) is presented through the development of a two-step method of symmetry breaking at the unrestricted Hartree-Fock level and of subsequent symmetry restoration via post Hartree-Fock projection techniques. Quantitative and qualitative aspects of the two-step method are treated and validated by exact diagonalization calculations.Strongly-correlated phenomena emerging from symmetry breaking include the following.Chemical bonding, dissociation and entanglement (at zero and finite magnetic fields) in quantum dot molecules and in pinned electron molecular dimers formed within a single anisotropic quantum dot, with potential technological applications to solid-state quantum-computing devices.Electron crystallization, with particle localization on the vertices of concentric polygonal rings, and formation of rotating electron molecules (REMs) in circular quantum dots. Such electron molecules exhibit ro-vibrational excitation spectra, in analogy with natural molecules.At high magnetic fields, the REMs are described by parameter-free analytic wave functions, which are an alternative to the Laughlin and composite-fermion approaches, offering a new point of view of the fractional quantum Hall regime in quantum dots (with possible implications for the thermodynamic limit).Crystalline phases of strongly repelling bosons. In rotating traps and in analogy with the REMs, such repelling bosons form rotating boson molecules (RBMs). For a small number of bosons, the RBMs are energetically favored compared with the Gross-Pitaevskii solutions describing vortex formation.We discuss the present status concerning experimental signatures of such strongly correlated states, in view of the promising outlook created by the latest experimental improvements that are achieving unprecedented control over the range and strength of interparticle interactions.
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Affiliation(s)
| | - Uzi Landman
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA
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18
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Obata T, Pioro-Ladrière M, Kubo T, Yoshida K, Tokura Y, Tarucha S. Microwave band on-chip coil technique for single electron spin resonance in a quantum dot. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:104704. [PMID: 17979446 DOI: 10.1063/1.2799735] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Microwave band on-chip microcoils are developed for the application to single electron spin resonance measurement with a single quantum dot. Basic properties such as characteristic impedance and electromagnetic field distribution are examined for various coil designs by means of experiment and simulation. The combined setup operates relevantly in the experiment at dilution temperature. The frequency responses of the return loss and Coulomb blockade current are examined. Capacitive coupling between a coil and a quantum dot causes photon assisted tunneling, whose signal can greatly overlap the electron spin resonance signal. To suppress the photon assisted tunneling effect, a technique for compensating for the microwave electric field is developed. Good performance of this technique is confirmed from measurement of Coulomb blockade oscillations.
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Affiliation(s)
- Toshiaki Obata
- Quantum Spin Information Project, ICORP, JST, Atsugi-shi, Kanagawa 243-0198, Japan
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Hu X, Das Sarma S. Charge-fluctuation-induced dephasing of exchange-coupled spin qubits. PHYSICAL REVIEW LETTERS 2006; 96:100501. [PMID: 16605716 DOI: 10.1103/physrevlett.96.100501] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 09/30/2005] [Indexed: 05/08/2023]
Abstract
Exchange-coupled spin qubits in semiconductor nanostructures are shown to be vulnerable to dephasing caused by charge noise invariably present in the semiconductor environment. This decoherence of exchange gate by environmental charge fluctuations arises from the fundamental Coulombic nature of the Heisenberg coupling and presents a serious challenge to the scalability of the widely studied exchange gate solid state spin quantum computer architectures. We estimate dephasing times for coupled spin qubits in a wide range (from 1 ns up to >1 micros) depending on the exchange coupling strength and its sensitivity to charge fluctuations.
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Affiliation(s)
- Xuedong Hu
- Department of Physics, University at Buffalo, The State University of New York, 239 Fronczak Hall, Buffalo, New York 14260-1500, USA
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20
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Stinaff EA, Scheibner M, Bracker AS, Ponomarev IV, Korenev VL, Ware ME, Doty MF, Reinecke TL, Gammon D. Optical Signatures of Coupled Quantum Dots. Science 2006; 311:636-9. [PMID: 16410487 DOI: 10.1126/science.1121189] [Citation(s) in RCA: 414] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.
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Affiliation(s)
- E A Stinaff
- Naval Research Laboratory, Washington, DC 20375, USA
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