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Existence of Majorana bounded states in a simple Josephson transition model. (Russian. English summary) Zbl 1441.81096

Summary: For the last 15 years, Majorana bounded states (MBSs) and associated phenomena, such as variation of conductance and the Josephson effect, have been actively studied in the physical literature. Research in this direction is motivated by a highly probable use of MBSs in quantum computing. The article studies the eigenfunctions of the one-dimensional Bogolyubov-de Gennes operator with a delta-shaped potential at zero, describing localized states with energy in the spectral gap (superconducting gap). The transmission probabilities are found in the scattering problem for this operator, when the energies are close to the boundary of the superconducting gap. These problems are studied both for a superconducting order that is the only one on the whole straight line and is defined by the real constant \(\Delta,\) and for a superconducting order defined by the function \(\Delta\theta(-x)+\Delta e^{i\varphi}\theta(x)\) for \(\varphi=0,\pi \) (i.e., for zero superconducting current and for current close to critical). The Hamiltonian used can be considered as the simplest model of the Josephson junction. It is proved that in both cases there are two MBSs, but with certain values of the parameters, i.e., MBSs are unstable. Moreover, the probability of passage is zero in both cases.

MSC:

81Q10 Selfadjoint operator theory in quantum theory, including spectral analysis
81Q15 Perturbation theories for operators and differential equations in quantum theory
46F10 Operations with distributions and generalized functions
82D55 Statistical mechanics of superconductors
35J08 Green’s functions for elliptic equations
35P05 General topics in linear spectral theory for PDEs
35P25 Scattering theory for PDEs

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