Quantum interference in non-ideal superconducting nanoring


Il giorno 5 Giugno 2020, dalle ore 14.30 alle ore 15.30, il Prof. Gian Paolo PAPARI terrà il seminario intitolato:

"Quantum interference in non-ideal superconducting nanoring"

Il seminario sarà telematico e andrà in onda sulla piattaforma Microsoft Teams, al Team "Seminari Fisica" raggiungibile qui



The interference process of transport electrons is a fascinating phenomenon firmly signing the wave like behavior of coherent currents. A mesoscopic ring represents the reference system to observe the interference dynamics of the wave function describing the state of currents flowing across a not simply connected channel.

Electronic interference experiments have a clear signature expressed by the harmonic oscillation of electrical observables depending on the flux of an external magnetic field. A few decades of accurate experiments and sophisticated theoretical models have produced a dense literature on mesoscopic mechanisms relating resistance oscillations to localization processes [1] [2]. However, the wide literature dedicated to magnetoresistance oscillations of superconducting samples, developed from the Little and Parks effect [3] addresses resistance oscillations to the periodical excitation of supercurrent ones, implying the lowering of superconducting stiffness as well.

The failure of Little and Parks model to justify the large amplitude of the magnetoresistance oscillations of high critical temperature superconducting nano-rings [4] [5] has motivated the development of a new approach where the interference of the wave function of the superconducting state is explicitly connected to the magnetoresistance. The model is verified on the measurements acquired on single high critical temperature superconducting nano rings whose magnetoresistance shows a double periodicity. We address this behavior to the non-ideal geometrical features and conditions in which a real sample is either realized and measured [6]. Localization of superconducting currents in correspondence of both the ring and nucleated vortices, results the driving mechanism to address the double periodicity observed in measurements. 

[1]       B. Al'Tshuler, A. Aronov, B. Spivak, D. Sharvin, Y. Sharvin, Observation of the Aaronov-Bohm effect in hollow metal cylinders, Sov. J. Exp. Theor. Phys. Lett. 35 (1982) 588.

[2]       V. Chandrasekhar, M.J. Rooks, S. Wind, D.E. Prober, Observation of Aharonov-Bohm electron interference effects with periods h/e and h/2e in individual micron-size, normal-metal rings, Pis'ma Zh. Eksp. Teor. Fiz. 35 (1982) 476–478. doi:10.1103/PhysRevLett.55.1610.

[3]       W.A. Little, R.D. Parks, observation of quantum periodicity in the transition temperature of a superconducting cylinder, Phys. Rev. Lett. 9 (1962) 9–12.

[4]       F. Carillo, G. Papari, D. Stornaiuolo, D. Born, D. Montemurro, P. Pingue, F. Beltram, F. Tafuri, Little-Parks effect in single nanoscale YBa2Cu3O6+x rings, Phys. Rev. B. 81 (2010) 054505. doi:10.1103/PhysRevB.81.054505.

[5]       I. Sochnikov, A. Shaulov, Y. Yeshurun, G. Logvenov, I. Božović, Oscillatory magnetoresistance in nanopatterned superconducting La1.84Sr0.16CuO4 films, Phys. Rev. B. 82 (2010) 094513. doi:10.1103/PhysRevB.82.094513.

[6]       G.P. Papari, V.M. Fomin, Interplay between the quantum interference and current localization phenomena in superconductor non-ideal mesoscopic rings, Supercond. Sci. Technol. 32 (2019). doi:10.1088/1361-6668/ab315f.

Data: 05/06/2020