English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

A generic semiclassical superconducting nanostructure connected to multiplesuperconducting terminals hosts a quasi-continuous spectrum of Andreev states.The spectrum is sensitive to the superconducting phases of the terminals. Itcan be either gapped or gapless depending on the point in the multi-dimensionalparametric space of these phases. Special points in this space correspond tosetting some terminals to the phase 0 and the rest to the phase of $\pi$. For ageneric nanostructure, three distinct spectra come together in the vicinity ofa special point: two gapped phases of different topology and a gapless phaseseparating the two by virtue of topological protection.  In this paper, we show that a weak interaction manifesting as quantumfluctuations of superconducting phases drastically changes the spectrum in anarrow vicinity of a special point. We develop an interaction model and derivea universal generic quantum action that describes this situation. The action iscomplicated by incorporating a non-local in time matrix order parameter, andits full analysis is beyond the scope of the present paper. Here, we identifyand address two limits: the semiclassical one and the quantum one,concentrating on the first-order interaction correction in the last case.  In both cases, we find that the interaction squeezes the domain of thegapless phase in the narrow vicinity of the point so the gapped phases tend tocontact each other immediately, defying the topological protection. We identifythe domains of strong coupling where the perturbation theory does not work. Inthe gapless phase, we find the logarithmic divergence of the first-ordercorrections. This leads us to an interesting hypothesis: weak interaction mightinduce an exponentially small gap in the formerly gapless phase.

Drastic effect of weak interaction near special points in semiclassical multiterminal superconducting nanostructures