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Quantum dot attached to topological wires has become an interesting setup
to study Majorana bound state in condensed matter[1]. One of the major
advantage of using a quantum dot for this purpose is that it provides a
suitable manner to study the interplay between Majorana bound states and
the Kondo effect.
Recently we have shown that a non-interacting quantum dot side-connected
to a 1D topological superconductor and to metallic normal leads can sustain
a Majorana mode even when the dot is empty. This is due to the Majorana bound
state of the wire leaking into the quantum dot. Now we investigate the system
for the case in which the quantum dot is interacting[3]. We explore the
signatures of a Majorana zero--mode leaking into the quantum dot, using a
recursive Green's function approach. We then study the Kondo regime using
numerical renormalization group calculations. In this regime, we show that a
"0.5" contribution to the conductance appears in system due to the
presence of the Majorana mode, and that it persists for a wide range of the dot
parameters. In the particle-hole symmetric point, in which the Kondo effect is
more robust, the total conductance reaches $3e^2/2h$, clearly indicating the
coexistence of a Majorana mode and the Kondo resonance in the dot.
However, the Kondo effect is suppressed by a gate voltage that detunes the
dot from its particle-hole symmetric point as well as by a Zeeman field. The
Majorana mode, on the other hand, is almost insensitive to both of them. We
show that the zero--bias conductance as a function of the magnetic field follows
a well--known universal curve. This can be observed experimentally, and we
propose that this universality followed by a persistent conductance of
$0.5,e^2/h$ are evidence for the presence of Majorana--Kondo physics.
This work is supported by the Brazilians agencies FAPESP, CNPq and
FAPEMIG.
[1] A. Y. Kitaev, Ann.Phys. {bf 303}, 2 (2003).
[2] E. Vernek, P.H. Penteado, A. C. Seridonio, J. C. Egues, Phys. Rev. B
{bf 89}, 165314 (2014).
[3] David A. Ruiz-Tijerina, E. Vernek, Luis G. G. V. Dias da Silva, J. C.
Egues, arXiv:1412.1851 [cond-mat.mes-hall].
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