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Posts tagged publication

PRB about 4 kinds of topology in a single device

Published about a month ago, actually.

Order, disorder, and tunable gaps in the spectrum of Andreev bound states in a multiterminal superconducting device
Tomohiro Yokoyama, Johannes Reutlinger, Wolfgang Belzig, and Yuli V. Nazarov

Phys. Rev. B 95, 045411 (2017) – Published 12 January 2017

The link to the arxiv version

PRB details omega-squid

I thought for a while I made a record publishing two independent papers on the same day – no such luck, still a day difference :(

Coherent transport properties of a three-terminal hybrid superconducting interferometer

F. Vischi, M. Carrega, E. Strambini, S. D’Ambrosio, F. S. Bergeret, Yu. V. Nazarov, and F. Giazotto

Phys. Rev. B 95, 054504 – Published 13 February 2017

The link to the arxiv version

PRB transconductance quantization

Topological transconductance quantization in a four-terminal Josephson junction

Erik Eriksson, Roman-Pascal Riwar, Manuel Houzet, Julia S. Meyer, and Yuli V. Nazarov

Phys. Rev. B 95, 075417 – Published 14 February 2017

The link to the arxiv version

Nature Nanotechnology: how to engineer topology

The engineering efforts reported in March made their way to Nature Nanotechnology on Sep. 12,
The ω-SQUIPT as a tool to phase-engineer Josephson topological materials

E. Strambini, S. D’Ambrosio, F. Vischi, F. S. Bergeret, Yu. V. Nazarov & F. Giazotto

Nature Nanotechnology (2016) doi:10.1038/nnano.2016.157

Full text can be accessed via this link

PRL quasiparticles

The attempt to unveil quasiparticle mysteries has been finally published in PRL

Theoretical Model to Explain Excess of Quasiparticles in Superconductors
Anton Bespalov, Manuel Houzet, Julia S. Meyer, and Yuli V. Nazarov
Phys. Rev. Lett. 117, 117002 – Published 9 September 2016

ABSTRACT: Experimentally, the concentration of quasiparticles in gapped superconductors always largely exceeds the equilibrium one at low temperatures. Since these quasiparticles are detrimental for many applications, it is important to understand theoretically the origin of the excess. We demonstrate in detail that the dynamics of quasiparticles localized at spatial fluctuations of the gap edge becomes exponentially slow. This gives rise to the observed excess in the presence of a vanishingly weak non-equilibrium agent.

Nature news and views

Quite unexpectedly, I’ve published something in Nature, specifically in News ans Views:

Quantum physics: Destruction of discrete charge

Electric charge is quantized in units of the electron’s charge. An experiment explores the suppression of charge quantization caused by quantum fluctuations and supports a long-standing theory that explains this behaviour. See Letter p.58

Yuli V. Nazarov

Nature 536, 38–39 (03 August 2016) | doi:10.1038/536038a

Full text can be seen here.

Nature Communications

Another publication with Grenoble friends. The preprint is available for almost a year, it had a complex history of submissions and interactions with referees :( Anyway, it feels like my best paper so far.

Title: Multi-terminal Josephson junctions as topological matter
Authors: Roman-Pascal Riwar, Manuel Houzet, Julia S. Meyer & Yuli V. Nazarov
Ref: Nature Communications 7, Article number: 11167, doi:10.1038/ncomms11167

Abstract: Topological materials and their unusual transport properties are now at the focus of modern experimental and theoretical research. Their topological properties arise from the bandstructure determined by the atomic composition of a material and as such are difficult to tune and naturally restricted to ≤3 dimensions. Here we demonstrate that n-terminal Josephson junctions with conventional superconductors may provide novel realizations of topology in n−1 dimensions, which have similarities, but also marked differences with existing 2D or 3D topological materials. For n≥4, the Andreev subgap spectrum of the junction can accommodate Weyl singularities in the space of the n−1 independent superconducting phases, which play the role of bandstructure quasimomenta. The presence of these Weyl singularities enables topological transitions that are manifested experimentally as changes of the quantized transconductance between two voltage-biased leads, the quantization unit being 4e2/h, where e is the electric charge and h is the Planck constant.

Density of states in gapped superconductors with pairing-potential impurities

This is the title of a recent publication with my Grenoble friends.
Phys. Rev. B 93, 104521 – Published 21 March 2016
Text at Arxive
We study the density of states in disordered s-wave superconductors with a small gap anisotropy. We consider disorder in the form of common nonmagnetic scatterers and pairing-potential impurities, which interact with electrons via an electric potential and a local distortion of the superconducting gap. Using quasiclassical Green functions, we determine the bound-state spectrum at a single impurity and the density of states at a finite concentration of impurities. We show that, if the gap is isotropic, an isolated impurity with suppressed pairing supports an infinite number of Andreev states. With growing impurity concentration, the energy-dependent density of states evolves from a sharp gap edge with an impurity band below it to a smeared BCS singularity in the so-called universal limit. Within one spin sector, pairing-potential impurities and weak spin-polarized magnetic impurities have essentially the same effect on the density of states. We note that, if a gap anisotropy is present, the density of states becomes sensitive to ordinary potential disorder, and the existence of Andreev states localized at pairing-potential impurities requires special conditions. An unusual feature related to the anisotropy is a nonmonotonic dependence of the gap edge smearing on impurity concentration.

Exact correspondence between Renyi entropy flows and physical flows

has been published today.
Reference: Mohammad H. Ansari and Yuli V. Nazarov, Phys. Rev. B 91, 174307 (2015)

Strong effects of weak ac driving in short superconducting junctions

has been published in PRB couple of days ago.
DOI: 10.1103/PhysRevB.91.104522

You can find the preprint here.

We study a short superconducting junction subject to a dc and ac phase bias. The ac modulation changes the occupation of the Andreev bound states formed at the constriction by transitions between bound states and the continuum. In a short junction, the non-equilibrium Andreev bound state population may relax through processes that conserve parity of the occupation number on the same bound state and processes that do not conserve it. We argue that the parity conserving processes occur on a much faster time scale. In this case, even a weak driving may lead to a large deviation of the supercurrent from its equilibrium value. We show that this effect is accompanied by a quasiparticle current which may lead to a measurable charge imbalance in the vicinity of the junction. Furthermore, we study the time evolution of the supercurrent after switching off the ac drive. On a time scale where parity relaxation is negligible, the supercurrent relaxes to a stationary non-equilibrium state. Finally, we briefly outline the regime of ultraweak driving where the ac-induced processes occur on a time scale comparable to parity relaxation.

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