Anthony R. Wright, Menno Veldhorst
We propose a superconductor double quantum dot system that hosts localized Majorana fermions in the presence of negligible Zeeman splitting. An anisotropic magnetic field, smaller than the thermal energy, produces different local fields on the dots. The inclusion of on-site Coulomb repulsion prevents local Andreev reflection and upon increasing the strength we find a clear phase transition. Above this transition, Majorana operators move the system between the odd parity ground state, associated with elastic co-tunneling, and the even parity ground state, associated with crossed Andreev reflection. These Majorana modes are described in terms of one, three and five operator products and become completely localized when the local fields on the dot are orthogonal. Parity conservation results in a 4pi periodic supercurrent in the even state and no supercurrent in the odd state. The necessity of only small magnetic fields and the broad parameter space where Majorana fermions appear simplifies the experimental realization greatly, paving the way towards the detection of the Majorana fermion.
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http://arxiv.org/abs/1303.1570
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