The Experts below are selected from a list of 66540 Experts worldwide ranked by ideXlab platform
Gianluigi Catelani - One of the best experts on this subject based on the ideXlab platform.
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Proximity Effect in normal-metal quasiparticle traps
Physical Review B, 2018Co-Authors: A. Hosseinkhani, Gianluigi CatelaniAbstract:In many superconducting devices, including qubits, quasiparticle excitations are detrimental. A normal metal ($N$) in contact with a superconductor ($S$) can trap these excitations; therefore such a trap can potentially improve the devices performances. The two materials influence each other, a phenomenon known as Proximity Effect which has drawn attention since the '60s. Here we study whether this mutual influence places a limitation on the possible performance improvement in superconducting qubits. We first revisit the Proximity Effect in uniform $NS$ bilayers; despite the long history of this problem, we present novel findings for the density of states. We then extend our results to describe a non-uniform system in the vicinity of a trap edge. Using these results together with a phenomenological model for the suppression of the quasiparticle density due to the trap, we find in a transmon qubit an optimum trap-junction distance at which the qubit relaxation rate is minimized. This optimum distance, of the order of 4 to 20 coherence lengths, originates from the competition between Proximity Effect and quasiparticle density suppression. We conclude that the harmful influence of the Proximity Effect can be avoided so long as the trap is farther away from the junction than this optimum.
Das S Sarma - One of the best experts on this subject based on the ideXlab platform.
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induced spectral gap and pairing correlations from superconducting Proximity Effect
Physical Review B, 2016Co-Authors: Chingkai Chiu, William S Cole, Das S SarmaAbstract:We theoretically consider superconducting Proximity Effect, using the Bogoliubov-de Gennes theory, in heterostructure sandwich-type geometries involving a normal s-wave superconductor and a non-superconducting material with the Proximity Effect being driven by Cooper pairs tunneling from the superconducting slab to the non-superconducting slab. Applications of the superconducting Proximity Effect may rely on an induced spectral gap or induced pairing correlations without any spectral gap. We clarify that in a non-superconducting material the induced spectral gap and pairing correlations are independent physical quantities arising from the Proximity Effect. This is a crucial issue in proposals to create topological superconductivity through the Proximity Effect. Heterostructures of 3D topological insulator (TI) slabs on conventional s-wave superconductor (SC) substrates provide a platform, with Proximity-induced topological superconductivity expected to be observed on the "naked" top surface of a thin TI slab. We theoretically study the induced superconducting gap on this naked surface. In addition, we compare against the induced spectral gap in heterostructures of SC with a normal metal or a semiconductor with strong spin orbit coupling and a Zeeman splitting potential (another platform for topological superconductivity). We find that for any model for the non-SC metal (including metallic TI) the induced spectral gap on the naked surface decays as $L^{-3}$ as the thickness ($L$) of the non-SC slab is increased in contrast to the slower $1/L$ decay of the pairing correlations. Our distinction between Proximity-induced spectral gap (with its faster spatial decay) and pairing correlation (with its slower spatial decay) has important implications for the currently active search for topological superconductivity and Majorana fermions in various superconducting heterostructures.
Alexandre I. Buzdin - One of the best experts on this subject based on the ideXlab platform.
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Long ranged singlet Proximity Effect in ferromagnetic nanowires
Physical Review B: Condensed Matter and Materials Physics, 2010Co-Authors: François Konschelle, Jérôme Cayssol, Alexandre I. BuzdinAbstract:Recently a long ranged superconductor/ferromagnet (S/F) Proximity Effect has been reported in Co crystalline nanowires [1, Nature, 6 389 (2010)]. Since the authors of [1] take care to avoid the existence of magnetic domains, the triplet character of the long ranged Proximity Effect is improbable. Here we demonstrate that in the one-dimensional ballistic regime the standard singlet S/F Proximity Effect becomes long ranged. We provide an exact solution for the decay of the superconducting correlations near critical temperature ($T_{c}$) and for arbitrary impurities concentration. In particular we find a specific regime, between the diffusive and ballistic ones, where the decay length is simply the electronic mean-free path. Finally possible experiments which could permit to elucidate the nature of the observed long ranged Proximity Effect in Co nanowires are discussed.
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Long-range singlet Proximity Effect in ferromagnetic nanowires
Physical Review B, 2010Co-Authors: François Konschelle, Jérôme Cayssol, Alexandre I. BuzdinAbstract:Recently a long-ranged superconductor/ferromagnet (S/F) Proximity Effect has been reported in Co crystalline nanowires [J. Wang, M. Singh, M. Tian, N. Kumar, B. Liu, C. Shi, J. K. Jain, N. Samarth, T. E. Mallouk, and M. H. W. Chan, Nat. Phys. 6, 389 (2010)]. Since the authors take care to avoid the existence of magnetic domains, the triplet character of the long-ranged Proximity Effect is improbable. Here we demonstrate that in the one-dimensional ballistic regime the standard singlet S/F Proximity Effect becomes long ranged. We provide an exact solution for the decay of the superconducting correlations near critical temperature (Tc) and for arbitrary impurities concentration. In particular, we find a specific regime, between the diffusive and ballistic ones, where the decay length is simply the electronic mean-free path. Finally possible experiments which could permit to elucidate the nature of the observed long-ranged Proximity Effect in Co nanowires are discussed.
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Proximity Effect in superconductor–ferromagnet heterostructures
Comptes Rendus Physique, 2006Co-Authors: Alexandre I. Buzdin, Valery V. RyazanovAbstract:We discuss the particularities of the Proximity Effect in superconductor–ferromagnet systems: the damped oscillatory behavior of the Cooper pair wave function, the oscillations of the critical temperature in S/F bilayers and multilayers and the conditions for the π-Josephson junctions formation. Also we outline the possibility of the formation of the novel type of the Josephson junction, intermediate between the 0 and π junctions
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Proximity Effect in superconductor/ferromagnet nanostructures
Physica C: Superconductivity and its Applications, 2006Co-Authors: Alexandre I. Buzdin, Marion FaureAbstract:We discuss the peculiarities of the Proximity Effect in superconductor/ferromagnet (S/F) hybrid structures. In S/F bilayers with a thin F layer, a very striking non-monotonous dependence of the critical temperature on the interface transparency is predicted. It is also demonstrated that the spin-flip scattering strongly affects the properties of S/F/S junctions. Finally, we study the ‘‘fine structure'' of the 0–p transition.
R. Morandotti - One of the best experts on this subject based on the ideXlab platform.
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Polarization Proximity Effect in isolator crystal pairs
2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum electronics and Laser Science Conference, 2009Co-Authors: Y. Linzon, M. Ferrera, L. Razzari, A. Pignolet, R. MorandottiAbstract:We experimentally study the polarization dynamics (orientation and ellipticity) of near infrared light transmitted through magnetooptic yttrium iron garnet isolator crystal pairs using a modified balanced detection scheme. When the pair separation is in the sub-millimeter range, we observed a Proximity Effect in which the saturation field is reduced by up to 20%. Calculations using a 1D model suggest that the Proximity Effect originates from magnetostatic interactions between the dipole moments of the isolator crystals.
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Polarization Proximity Effect in isolator crystal pairs
Optics letters, 2008Co-Authors: Y. Linzon, M. Ferrera, L. Razzari, A. Pignolet, R. MorandottiAbstract:We experimentally studied the polarization dynamics (orientation and ellipticity) of near infrared light transmitted through magnetooptic Yttrium Iron Garnet crystal pairs using a modified balanced detection scheme. When the pair separation is in the sub-millimeter range, we observed a Proximity Effect in which the saturation field is reduced by up to 20%. 1D magnetostatic calculations suggest that the Proximity Effect originates from magnetostatic interactions between the dipole moments of the isolator crystals. This substantial reduction of the saturation field is potentially useful for the realization of low-power integrated magneto-optical devices.
A. Hosseinkhani - One of the best experts on this subject based on the ideXlab platform.
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Proximity Effect in normal-metal quasiparticle traps
Physical Review B, 2018Co-Authors: A. Hosseinkhani, Gianluigi CatelaniAbstract:In many superconducting devices, including qubits, quasiparticle excitations are detrimental. A normal metal ($N$) in contact with a superconductor ($S$) can trap these excitations; therefore such a trap can potentially improve the devices performances. The two materials influence each other, a phenomenon known as Proximity Effect which has drawn attention since the '60s. Here we study whether this mutual influence places a limitation on the possible performance improvement in superconducting qubits. We first revisit the Proximity Effect in uniform $NS$ bilayers; despite the long history of this problem, we present novel findings for the density of states. We then extend our results to describe a non-uniform system in the vicinity of a trap edge. Using these results together with a phenomenological model for the suppression of the quasiparticle density due to the trap, we find in a transmon qubit an optimum trap-junction distance at which the qubit relaxation rate is minimized. This optimum distance, of the order of 4 to 20 coherence lengths, originates from the competition between Proximity Effect and quasiparticle density suppression. We conclude that the harmful influence of the Proximity Effect can be avoided so long as the trap is farther away from the junction than this optimum.
