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Lau, A. (author), Ray, Rajyavardhan (author), Varjas, D. (author), Akhmerov, A.R. (author)We study the influence of sample termination on the electronic properties of the novel quantum spin Hall insulator monolayer 1T′-WTe2. For this purpose, we construct an accurate, minimal four-orbital tight-binding model with spin-orbit coupling by employing a combination of density-functional theory calculations, symmetry considerations, and...journal article 2019
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Nowak, M. P. (author), Wimmer, M.T. (author), Akhmerov, A.R. (author)We theoretically study coherent multiple Andreev reflections in a biased three-terminal Josephson junction. We demonstrate that the direct current flowing through the junction consists of supercurrent components when the bias voltages are commensurate. This dissipationless current depends on the phase in the superconducting leads and stems...journal article 2019
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Varjas, D. (author), Lau, A. (author), Pöyhönen, K.K. (author), Akhmerov, A.R. (author), Pikulin, Dmitry I. (author), Fulga, Ion Cosma (author)We construct a two-dimensional higher-order topological phase protected by a quasicrystalline eightfold rotation symmetry. Our tight-binding model describes a superconductor on the Ammann-Beenker tiling hosting localized Majorana zero modes at the corners of an octagonal sample. In order to analyze this model, we introduce Hamiltonians...journal article 2019
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Vuik, A. (author), Nijholt, B. (author), Akhmerov, A.R. (author), Wimmer, M.T. (author)Andreev bound states in hybrid superconductor-semiconductor devices can have near-zero energy in the topologically trivial regime as long as the confinement potential is sufficiently smooth. These quasi-Majorana states show zero-bias conductance features in a topologically trivial phase, mimicking spatially separated topological Majorana...journal article 2019
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Walter, E. (author), Rosdahl, T.O. (author), Akhmerov, A.R. (author), Hassler, F (author)The law of reflection states that smooth surfaces reflect waves specularly, thereby acting as a mirror. This law is insensitive to disorder as long as its length scale is smaller than the wavelength. Monolayer graphene exhibits a linear dispersion at low energies and consequently a diverging Fermi wavelength. We present proof that for a...journal article 2018
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O'Brien, T. E. (author), Rozek, P.M. (author), Akhmerov, A.R. (author)Because Majorana zero modes store quantum information nonlocally, they are protected from noise, and have been proposed as a building block for a quantum computer. We show how to use the same protection from noise to implement universal fermionic quantum computation. Our architecture requires only two Majorana modes to encode a fermionic...journal article 2018
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Istas, Mathieu (author), Groth, Christoph (author), Akhmerov, A.R. (author), Wimmer, M.T. (author), Waintal, Xavier (author)We propose a robust and efficient algorithm for computing bound states of infinite tight-binding systems that are made up of a finite scattering region connected to semi-infinite leads. Our method uses wave matching in close analogy to the approaches used to obtain propagating states and scattering matrices. We show that our algorithm is robust...journal article 2018
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Varjas, D. (author), Rosdahl, T.O. (author), Akhmerov, A.R. (author)Symmetry is a guiding principle in physics that allows us to generalize conclusions between many physical systems. In the ongoing search for new topological phases of matter, symmetry plays a crucial role by protecting topological phases. We address two converse questions relevant to the symmetry classification of systems: is it possible to...journal article 2018
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Sticlet, D.C. (author), Sau, Jay D. (author), Akhmerov, A.R. (author)The anomalous 4π-periodic ac Josephson effect, a hallmark of topological Josephson junctions, was experimentally observed in a quantum spin Hall insulator. This finding is unexpected due to time-reversal symmetry preventing the backscattering of the helical edge states and therefore suppressing the 4π-periodic component of the Josephson...journal article 2018
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Rosdahl, T.O. (author), Vuik, A. (author), Kjaergaard, M. (author), Akhmerov, A.R. (author)The proximity effect in hybrid superconductor-semiconductor structures, crucial for realizing Majorana edge modes, is complicated to control due to its dependence on many unknown microscopic parameters. In addition, defects can spoil the induced superconductivity locally in the proximitized system, which complicates measuring global...journal article 2018
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Kraft, Rainer (author), Mohrmann, Jens (author), Du, Renjun (author), Selvasundaram, Pranauv Balaji (author), Irfan, M. (author), Kanilmaz, Umut Nefta (author), Wu, F. (author), Beckmann, Detlef (author), Von Löhneysen, Hilbert (author), Krupke, Ralph (author), Akhmerov, A.R. (author), Gornyi, Igor (author), Danneau, Romain (author)The Josephson effect is one of the most studied macroscopic quantum phenomena in condensed matter physics and has been an essential part of the quantum technologies development over the last decades. It is already used in many applications such as magnetometry, metrology, quantum computing, detectors or electronic refrigeration. However,...journal article 2018
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Allen, Monica T. (author), Shtanko, Oles (author), Fulga, Ion C. (author), Wang, Joel I.J. (author), Nurgaliev, Daniyar (author), Watanabe, Kenji (author), Taniguchi, Takashi (author), Akhmerov, A.R. (author), Jarillo-Herrero, Pablo (author), Levitov, Leonid S. (author), Yacoby, Amir (author)Electron surface states in solids are typically confined to the outermost atomic layers and, due to surface disorder, have negligible impact on electronic transport. Here, we demonstrate a very different behavior for surface states in graphene. We probe the wavelike character of these states by Fabry-Perot (FP) interferometry and find that,...journal article 2017
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Zuo, K. (author), Mourik, V. (author), Szombati, D.B. (author), Nijholt, B. (author), van Woerkom, D.J. (author), Geresdi, A. (author), Chen, Jun (author), Ostroukh, Viacheslav P. (author), Akhmerov, A.R. (author), Plissard, S.R. (author), Car, D. (author), Bakkers, E.P.A.M. (author), Pikulin, Dmitry I. (author), Kouwenhoven, Leo P. (author), Frolov, S.M. (author)Junctions created by coupling two superconductors via a semiconductor nanowire in the presence of high magnetic fields are the basis for the potential detection, fusion, and braiding of Majorana bound states. We study NbTiN/InSb nanowire/NbTiN Josephson junctions and find that the dependence of the critical current on the magnetic field...journal article 2017
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Sticlet, D.C. (author), Nijholt, B. (author), Akhmerov, A.R. (author)We study the effects of strong coupling between a superconductor and a semiconductor nanowire on the creation of the Majorana bound states, when the quasiparticle dwell time in the normal part of the nanowire is much shorter than the inverse superconducting gap. This "short-junction" limit is relevant for the recent experiments using the...journal article 2017
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Kjaergaard, M. (author), Suominen, H. J. (author), Nowak, M.P. (author), Akhmerov, A.R. (author), Shabani, J. (author), Palmstrøm, C. J. (author), Nichele, F. (author), Marcus, C.M. (author)Measurement of multiple Andreev Reflection (MAR) in a Josephson junction made from an InAs quantum well heterostructure with epitaxial aluminum is used to quantify a highly transparent effective semiconductor-superconductor interface with near-unity transmission. The observed temperature dependence of MAR does not follow a conventional BCS...journal article 2017
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Sticlet, D.C. (author), Akhmerov, A.R. (author)We report an attractive critical point occurring in the Anderson localization scaling flow of symplectic models on fractals. The scaling theory of Anderson localization predicts that in disordered symplectic two-dimensional systems weak-antilocalization effects lead to a metal-insulator transition. This transition is characterized by a...journal article 2016
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Kjaergaard, M. (author), Nichele, F. (author), Suominen, H. J. (author), Nowak, M.P. (author), Wimmer, M (author), Akhmerov, A.R. (author), Folk, JA (author), Flensberg, K. (author), Shabani, J. (author), Palmstrøm, C. J. (author), Marcus, C. M. (author)Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards topological matter is by coupling a 2D electron gas...journal article 2016
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Rubbert, S.H.P. (author), Akhmerov, A.R. (author)Majorana bound states (MBS) differ from the regular zero energy Andreev bound states in their nonlocal properties, since two MBS form a single fermion. We design strategies for detection of this nonlocality by using the phenomenon of Coulomb-mediated Majorana coupling in a setting which still retains falsifiability and does not require...journal article 2016
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Ostroukh, V. P. (author), Baxevanis, B. (author), Akhmerov, A.R. (author), Beenakker, C.I.M. (author)The critical current of a Josephson junction is an oscillatory function of the enclosed magnetic flux Φ, because of quantum interference modulated with periodicity h/2e. We calculate these Fraunhofer oscillations in a two-dimensional (2D) ballistic superconductor-normal-metal-superconductor (SNS) junction. For a Fermi circle the amplitude of...journal article 2016
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Nijholt, B. (author), Akhmerov, A.R. (author)Studies of Majorana bound states in semiconducting nanowires frequently neglect the orbital effect of a magnetic field. Systematically studying its role leads us to several conclusions for designing Majoranas in this system. Specifically, we show that for experimentally relevant parameter values the orbital effect of a magnetic field has a...journal article 2016