Kavli Affiliate: Natalia Chepiga
| First 5 Authors: Rik Mulder, Bowy M. La Rivière, Natalia Chepiga, ,
| Summary:
We report the appearance of exact zero modes in junctions of interacting
Majorana wires. We consider two, three and four short Majorana chains coupled
to each other at one edge and forming a longer chain with an impurity bond, Y-
and X- junctions correspondingly. The exact zero modes emerge as a result of
incommensurate short-range correlations resulting from interacting Majorana
fermions and manifest themselves as unavoided crossing of energy levels of
in-gap states continuously tuned by hopping and interaction strength. For the
Y- and X-junctions, we detect four in-gap states that are clearly visible below
the bulk excitations. In the X-junction, the energy levels cross pairwise; in
the Y-junction, the crossings happen simultaneously in all four levels. We
argue that this peculiarity is a result of fractional degrees of freedom
localized at the center of junctions with an odd number of arms, which mediate
the interaction of the outer edge states. Furthermore, we show that zero modes
in multiple-arm junctions can be effectively modeled by a single chain with a
strong impurity bond.
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