Topological bound states

Горбацевич, А. А.; Zhuravlev, M. N.

doi:10.1134/s0021364009200077

Cited by 3 publications

(4 citation statements)

References 12 publications

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“…It is worth noting that a t-odd polar vector has a symmetry of a toroid moment[22]. The "phase generation" effect in a hypothetical superconductor with a toroidal ordering was discussed long ago in ref [23]…”

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confidence: 99%

Theory of diffusive φ ₀ Josephson junctions in the presence of spin-orbit coupling

Bergeret¹,

Tokatly²

2015

EPL

102

118

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We present a full microscopic theory based on the SU(2) covariant formulation of the quasiclassical formalism to describe the Josephson current through an extended superconductor-normal metalsuperconductor (SNS) diffusive junction with an intrinsic spin-orbit coupling (SOC) in the presence of a spin-splitting field h. We demonstrate that the ground state of the junction corresponds to a finite intrinsic phase difference 0 < ϕ0 < 2π between the superconductor electrodes provided that both, h and the SOC-induced SU(2) Lorentz force are finite. In the particular case of a Rashba SOC we present analytic and numerical results for ϕ0 as a function of the strengths of the spin fields, the length of the junction, the temperature and the properties of SN interfaces.The dc Josephson effect establishes that the supercurrent flowing between two superconductors connected by a weak link (normal metal, ferromagnet or semiconductor) is given by I J = I c sin ϕ . Here ϕ is the phase difference between the superconducting electrodes and I c the critical current, i.e. the maximum supercurrent that can flow through the junction. The ground state of such a junction corresponds to a zero current state and vanishing phase difference and for that reason it is denoted as a 0-junction. In analogy, one can define a ϕ 0 -junction with a more general current phase relation described byThe ground state corresponds to a finite phase difference ϕ 0 across the junction. Examples of non-zero junctions are superconductor-ferromagnet-superconductor (SFS) junction of certain thickness with a ground state at ϕ 0 = π, predicted in 1982 [1] and first detected in 2001 by Ryazanov et al. [2]. Besides 0 and π junctions currently there is no experimental evidence of a ϕ 0 -junction with 0 < ϕ 0 < π for single junctions [3][4][5]. It was, however, theoretically suggested by A. Buzdin [6] that if the weak link is made of a non-centrosymmetric magnetic metal such a junction is possible. This prediction has been originally formulated in terms of the Ginzburg-Landau (G-L) theory written in the presence of a Rashba-like SOC and an exchange field. ϕ 0 -junctions have been also analyzed in different types of ballistic junctions with the Rashba SOC [7]. The universality of this result in the presence of disorder or a generic SOC is however questionable, and no further conclusions can be drawn from previous works.In this letter we address this question and present a complete theoretical description of the Josephson effect through a weak link with arbitrary linear in momentum SOC and disorder. First, by using the analogy of SOC to a SU(2) gauge field and simple symmetry arguments we set the conditions for the ϕ 0 -junction to exist in a ballistic system, and demonstrate the connection between ϕ 0 -junction behavior and the Edelstein effect in superconductors [8]. In a second part we use the SU(2) covariant Eilenberger equation [9] to show that SOC-induced SU(2) Lorentz force is responsible for the intrinsic ϕ 0 for an arbitrary degree of disorder. Finally we analyze ...

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confidence: 99%

Theory of diffusive φ ₀ Josephson junctions in the presence of spin-orbit coupling

Bergeret¹,

Tokatly²

2015

EPL

102

118

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“…Examples for possible applications are shown in Figure : For a Josephson junction consisting of two superconductors separated by an insulating barrier, the local laser‐driven toroidal moment generated atop the structure drives a supercurrent across the junction. This is readily deduced from a Ginzburg–Landau formulation in which the free‐energy density contains the Lifshitz‐type invariant

0true \propto bold-italicT v_{s} \propto \sum_{i} T_{i} \partial_{{boldr}_{i}} φ_{s}

, meaning that

bold-italicT

couples directly to the superfluid velocity

v_{s}

or to spatial (

boldr

) variations in the condensate phase

φ_{s}

…”

Section: Introductionmentioning

confidence: 99%

“…This is readily deduced from a Ginzburg-Landau formulation in which the free-energy density contains the Lifshitz-type invariant ∝ T v s ∝ i T i ∂ r i ϕ s , meaning that T couples directly to the superfluid velocity v s or to spatial (r) variations in the condensate phase ϕ s . [27][28][29] Thus, our T acts as a direct THz switch for controlling the Josephson junction which are widely discussed for phase-qbits Application of the optically generated toroidal moment T : two time-delayed few-cycle moderate intense THz pulses with appropriately shaped polarization generate in a donut shaped nanostructure (indicated) within picoseconds a steady-state toroidal moment T (denoted by the fat white arrow) with no surrounding electric nor magnetic fields. When deposited on a Josephson junction or on a superconductor/ferromagnetic tunnel junction, T modifies locally the phase of the superconducting state, launching a supercurrent across the junction with properties tunable by the THz pulses.…”

Section: Introductionmentioning

confidence: 99%

“…consisting of two superconductors separated by an insulating barrier, the local laser-driven toroidal moment generated atop the structure drives a supercurrent across the junction. This is readily deduced from a Ginzburg-Landau-formulation in which the free-energy density contains the Lifshitz-type invariant ∝ Tv s ∝ i T i ∂ ri ϕ s , meaning that T couples directly to the superfluid velocity v s or to spatial (r) variations in the condensate phase ϕ s [31][32][33]. Thus, our T acts as a direct THz switch for controlling the Josephson junction which are widely discussed for phaseqbits quantum computing [34].…”

Section: Introductionmentioning

confidence: 99%

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Open‐Circuit Ultrafast Generation of Nanoscopic Toroidal Moments: The Swift Phase Generator

Wätzel

Berakdar

2018

Adv Quantum Tech

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Efficient and flexible schemes for a swift, field‐free control of the phase in quantum devices have far‐reaching impact on energy‐saving operation of quantum computing, data storage, and sensoring nanodevices. A novel approach for an ultrafast generation of a field‐free vector potential that is tunable in duration, sign, and magnitude, allowing to impart non‐invasive, spatiotemporally controlled changes to the quantum nature of nanosystems is reported. The method relies on triggering a steady‐state toroidal moment in a donut‐shaped nanostructure that serves as a vector‐potential generator and quantum phase modulator. Irradiated by moderately intense, few cycle THz pulses with appropriately shaped polarization states, the nano donut is brought to a steady‐state where a nearby object does not experience electric or magnetic fields but feels the photo‐generated vector potential. Designing the time structure of the driving THz pulses allows for launching picosecond trains of vector potentials which is the key for a contact‐free optimal control of quantum coherent states. This research can trigger a new class of ultrafast quantum devices operated and switched in an energy‐efficient, contact and field‐free manner, enabling new techniques for use in quantum information, magnetic nanostructures, and superconducting tunnel junctions as well as in toroidally ordered systems and multiferroics.

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Localized electronic states in branching polyacetylene molecules

Горбацевич

Zhuravlev

2015

Jetp Lett.

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Topological bound states

Cited by 3 publications

References 12 publications

Theory of diffusive φ ₀ Josephson junctions in the presence of spin-orbit coupling

Theory of diffusive φ ₀ Josephson junctions in the presence of spin-orbit coupling

Open‐Circuit Ultrafast Generation of Nanoscopic Toroidal Moments: The Swift Phase Generator

Localized electronic states in branching polyacetylene molecules

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Topological bound states

Cited by 3 publications

References 12 publications

Theory of diffusive φ 0 Josephson junctions in the presence of spin-orbit coupling

Theory of diffusive φ 0 Josephson junctions in the presence of spin-orbit coupling

Open‐Circuit Ultrafast Generation of Nanoscopic Toroidal Moments: The Swift Phase Generator

Localized electronic states in branching polyacetylene molecules

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Product

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About

Theory of diffusive φ ₀ Josephson junctions in the presence of spin-orbit coupling

Theory of diffusive φ ₀ Josephson junctions in the presence of spin-orbit coupling