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Triola, Christopher
Publications (3 of 3) Show all publications
Triola, C. & Black-Schaffer, A. M. (2019). Odd-frequency pairing in a superconductor coupled to two parallel nanowires. Physical Review B, 100(2), Article ID 024512.
Open this publication in new window or tab >>Odd-frequency pairing in a superconductor coupled to two parallel nanowires
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 2, article id 024512Article in journal (Refereed) Published
Abstract [en]

We study the behavior of Cooper pair amplitudes that emerge when a two-dimensional superconductor is coupled to two parallel nanowires, focusing on the conditions for realizing odd-frequency pair amplitudes in the absence of spin-orbit coupling or magnetism. In general, any finite tunneling between the superconductor and the two nanowires induces odd-frequency spin-singlet pair amplitudes in the substrate as well as a substantial odd-frequency interwire pairing, both of which vanish locally. Interestingly, in the regime of strong superconductor-nanowire tunneling, we find that the presence of two nanowires allows for the conversion of nonlocal odd-frequency pairing to local even-frequency pairing. By studying this higher-order symmetry conversion process, we are able to identify a notable effect of the odd-frequency pairing in the superconductor on local quantities accessible by experiments. Specifically, we find that the odd-frequency pairing plays a direct role in the emergence of certain subgap features in the local density of states and, importantly, it is responsible for a reduction of the maximum Josephson current between the two nanowires, measurable using Josephson scanning tunneling microscopy. We discuss ways to control the sizes of these effects induced by odd-frequency superconductivity by tuning the parameters describing the nanowires.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-391938 (URN)10.1103/PhysRevB.100.024512 (DOI)000476686100005 ()
Funder
Swedish Research Council, 621-2014-3721Knut and Alice Wallenberg FoundationEU, Horizon 2020, ERC-2017-StG-757553
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29Bibliographically approved
Triola, C. & Black-Schaffer, A. M. (2019). Odd-frequency superconductivity induced by nonmagnetic impurities. Physical Review B, 100(14), Article ID 144511.
Open this publication in new window or tab >>Odd-frequency superconductivity induced by nonmagnetic impurities
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 14, article id 144511Article in journal (Refereed) Published
Abstract [en]

A growing body of literature suggests that odd-frequency superconducting pair amplitudes can be generated in normal-metal-superconductor junctions. The emergence of odd-frequency pairing in these systems is often attributed to the breaking of translation invariance. In this work, we study the pair symmetry of a one-dimensional s-wave superconductor in the presence of a single nonmagnetic impurity and demonstrate that translation-symmetry breaking is not sufficient for inducing odd-frequency pairing. We consider three kinds of impurities: a local perturbation of the chemical potential, an impurity possessing a quantum energy level, and a local perturbation of the superconducting gap. Surprisingly, we find local perturbations of the chemical potential do not induce any odd-frequency pairing, despite the fact that they break translation invariance. Moreover, although odd frequency can be induced by both the quantum impurity and the perturbation of the gap, we find these odd-frequency amplitudes emerge from entirely different kinds of scattering processes. The quantum impurity generates odd-frequency pairs by allowing one of the quasiparticles belonging to an equal-time Cooper pair to tunnel onto the impurity state and then back to the superconductor, giving rise to odd-frequency amplitudes with a temporal broadening inversely proportional to the energy level of the impurity. In contrast to this, the perturbation of the gap leads to odd-frequency pairing by "gluing together" normal-state quasiparticles from different points in space and time, leading to odd-frequency amplitudes which are very localized in the time domain.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-396706 (URN)10.1103/PhysRevB.100.144511 (DOI)000491167700005 ()
Funder
Swedish Research Council, 621-2014-3721Swedish Research Council, 2018-03488Knut and Alice Wallenberg FoundationEU, European Research Council, ERC-2017-StG-757553
Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2019-11-08Bibliographically approved
Langmann, E., Triola, C. & Balatsky, A. V. (2019). Ubiquity of Superconducting Domes in the Bardeen-Cooper-Schrieffer Theory with Finite-Range Potentials. Physical Review Letters, 122(15), Article ID 157001.
Open this publication in new window or tab >>Ubiquity of Superconducting Domes in the Bardeen-Cooper-Schrieffer Theory with Finite-Range Potentials
2019 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 122, no 15, article id 157001Article in journal (Refereed) Published
Abstract [en]

Based on recent progress in mathematical physics, we present a reliable method to analytically solve the linearized Bardeen-Cooper-Schrieffer (BCS) gap equation for a large class of finite-range interaction potentials leading to s-wave superconductivity. With this analysis, we demonstrate that the monotonic growth of the superconducting critical temperature Tc with the carrier density n predicted by standard BCS theory, is an artifact of the simplifying assumption that the interaction is quasilocal. In contrast, we show that any well-defined nonlocal potential leads to a "superconducting dome," i.e., a nonmonotonic Tc(n) exhibiting a maximum value at finite doping and going to zero for large n. This proves that, contrary to conventional wisdom, the presence of a superconducting dome is not necessarily an indication of competing orders, nor of exotic superconductivity.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-382840 (URN)10.1103/PhysRevLett.122.157001 (DOI)000465182200011 ()31050533 (PubMedID)
Funder
Swedish Research Council, 621-2014-3721Swedish Research Council, 2016-05167Swedish Research Council, 2017-03997Knut and Alice Wallenberg Foundation
Available from: 2019-05-20 Created: 2019-05-20 Last updated: 2019-05-20Bibliographically approved
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