6π Josephson Effect in Majorana Box Devices

A. Zazunov; F. Buccheri; P. Sodano; R. Egger

doi:10.1103/PhysRevLett.118.057001

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6π Josephson Effect in Majorana Box Devices

A. Zazunov, F. Buccheri, P. Sodano, R. Egger

DOI 10.1103/PhysRevLett.118.057001 · Physical Review Letters

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Abstract

We study Majorana devices featuring a competition between superconductivity and multichannel Kondo physics. Our proposal extends previous work on single-channel Kondo systems to a topologically nontrivial setting of a non-Fermi liquid type, where topological superconductor wires (with gap Δ) represent leads tunnel coupled to a Coulomb-blockaded Majorana box. On the box, a spin degree of freedom with Kondo temperature TK is nonlocally defined in terms of Majorana states. For Δ≫TK, the destruction of Kondo screening by superconductivity implies a 4π-periodic Josephson current-phase relation. Using a strong-coupling analysis in the opposite regime Δ≪TK, we find a 6π-periodic Josephson relation for three leads, with critical current Ic≈eΔ2/ℏTK, corresponding to the transfer of fractionalized charges e*=2e/3.