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Du L, Liu Z, Wind SJ, Pellegrini V, West KW, Fallahi S, Pfeiffer LN, Manfra MJ, Pinczuk A. Observation of Flat Bands in Gated Semiconductor Artificial Graphene. PHYSICAL REVIEW LETTERS 2021; 126:106402. [PMID: 33784167 DOI: 10.1103/physrevlett.126.106402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
Flat bands near M points in the Brillouin zone are key features of honeycomb symmetry in artificial graphene (AG) where electrons may condense into novel correlated phases. Here we report the observation of van Hove singularity doublet of AG in GaAs quantum well transistors, which presents the evidence of flat bands in semiconductor AG. Two emerging peaks in photoluminescence spectra tuned by backgate voltages probe the singularity doublet of AG flat bands and demonstrate their accessibility to the Fermi level. As the Fermi level crosses the doublet, the spectra display dramatic stability against electron density, indicating interplays between electron-electron interactions and honeycomb symmetry. Our results provide a new flexible platform to explore intriguing flat band physics.
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Affiliation(s)
- Lingjie Du
- School of Physics, and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - Ziyu Liu
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - Shalom J Wind
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - Vittorio Pellegrini
- Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, I-16163 Genova, Italy
| | - Ken W West
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Saeed Fallahi
- Department of Physics and Astronomy, and School of Materials Engineering, and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Loren N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Michael J Manfra
- Department of Physics and Astronomy, and School of Materials Engineering, and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Aron Pinczuk
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
- Department of Physics, Columbia University, New York, New York 10027, USA
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Di Paola DM, Kesaria M, Makarovsky O, Velichko A, Eaves L, Mori N, Krier A, Patanè A. Resonant Zener tunnelling via zero-dimensional states in a narrow gap diode. Sci Rep 2016; 6:32039. [PMID: 27535896 PMCID: PMC4989182 DOI: 10.1038/srep32039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Accepted: 07/26/2016] [Indexed: 11/09/2022] Open
Abstract
Interband tunnelling of carriers through a forbidden energy gap, known as Zener tunnelling, is a phenomenon of fundamental and technological interest. Its experimental observation in the Esaki p-n semiconductor diode has led to the first demonstration and exploitation of quantum tunnelling in a condensed matter system. Here we demonstrate a new type of Zener tunnelling that involves the resonant transmission of electrons through zero-dimensional (0D) states. In our devices, a narrow quantum well of the mid-infrared (MIR) alloy In(AsN) is placed in the intrinsic (i) layer of a p-i-n diode. The incorporation of nitrogen in the quantum well creates 0D states that are localized on nanometer lengthscales. These levels provide intermediate states that act as "stepping stones" for electrons tunnelling across the diode and give rise to a negative differential resistance (NDR) that is weakly dependent on temperature. These electron transport properties have potential for the development of nanometre-scale non-linear components for electronics and MIR photonics.
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Affiliation(s)
- D M Di Paola
- School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK
| | - M Kesaria
- Physics Department, Lancaster University, Lancaster LA1 4YB, UK
| | - O Makarovsky
- School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK
| | - A Velichko
- School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK
| | - L Eaves
- School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK
| | - N Mori
- Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita City, Osaka 565-0871, Japan
| | - A Krier
- Physics Department, Lancaster University, Lancaster LA1 4YB, UK
| | - A Patanè
- School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK
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Longitudinal wave function control in single quantum dots with an applied magnetic field. Sci Rep 2015; 5:8041. [PMID: 25624018 PMCID: PMC4306960 DOI: 10.1038/srep08041] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/29/2014] [Indexed: 12/04/2022] Open
Abstract
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.
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Controlling the shannon entropy of quantum systems. THESCIENTIFICWORLDJOURNAL 2013; 2013:381219. [PMID: 23818819 PMCID: PMC3683499 DOI: 10.1155/2013/381219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 04/26/2013] [Indexed: 11/17/2022]
Abstract
This paper proposes a new quantum control method which controls the Shannon entropy of quantum systems. For both discrete and continuous entropies, controller design methods are proposed based on probability density function control, which can drive the quantum state to any target state. To drive the entropy to any target at any prespecified time, another discretization method is proposed for the discrete entropy case, and the conditions under which the entropy can be increased or decreased are discussed. Simulations are done on both two- and three-dimensional quantum systems, where division and prediction are used to achieve more accurate tracking.
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Teichmann K, Wenderoth M, Prüser H, Pierz K, Schumacher HW, Ulbrich RG. Harmonic oscillator wave functions of a self-assembled InAs quantum dot measured by scanning tunneling microscopy. NANO LETTERS 2013; 13:3571-3575. [PMID: 23777509 DOI: 10.1021/nl401217q] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
InAs quantum dots embedded in an AlAs matrix inside a double barrier resonant tunneling diode are investigated by cross-sectional scanning tunneling spectroscopy. The wave functions of the bound quantum dot states are spatially and energetically resolved. These bound states are known to be responsible for resonant tunneling phenomena in such quantum dot diodes. The wave functions reveal a textbook-like one-dimensional harmonic oscillator behavior showing up to five equidistant energy levels of 80 meV spacing. The derived effective oscillator mass of m* = 0.24m0 is 1 order of magnitude higher than the effective electron mass of bulk InAs that we attribute to the influence of the surrounding AlAs matrix. This underlines the importance of the matrix material for tailored QD devices with well-defined properties.
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Affiliation(s)
- Karen Teichmann
- IV. Physikalisches Institut, University of Göttingen, Göttingen, Germany
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Makarovsky O, Vdovin EE, Patané A, Eaves L, Makhonin MN, Tartakovskii AI, Hopkinson M. Laser location and manipulation of a single quantum tunneling channel in an InAs quantum dot. PHYSICAL REVIEW LETTERS 2012; 108:117402. [PMID: 22540507 DOI: 10.1103/physrevlett.108.117402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Indexed: 05/31/2023]
Abstract
We use a femtowatt focused laser beam to locate and manipulate a single quantum tunneling channel associated with an individual InAs quantum dot within an ensemble of dots. The intensity of the directed laser beam tunes the tunneling current through the targeted dot with an effective optical gain of 10(7) and modifies the curvature of the dot's confining potential and the spatial extent of its ground state electron eigenfunction. These observations are explained by the effect of photocreated hole charges which become bound close to the targeted dot, thus acting as an optically induced gate electrode.
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Affiliation(s)
- O Makarovsky
- School of Physics and Astronomy, The University of Nottingham, United Kingdom
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