Sunday, August 4, 2013

1308.0092 (E. Vernek et al.)

Majorana sneakily leaking into a quantum dot connected to a Kitaev wire    [PDF]

E. Vernek, P. H. Penteado, A. C. Seridonio, J. C. Egues
We investigate quantum transport through a quantum dot connected to source and drain leads and side coupled to a topological superconducting nanowire (Kitaev chain) sustaining Majorana end modes. Using a recursive Green's function approach, we determine the local density of states of the system and find that the end Majorana mode of the wire leaks into the dot thus emerging as a unique dot level pinned to the Fermi energy $\e_F$ of the leads. Quite surprisingly, this resonance pinning, resembling in this sense a "Kondo resonance", occurs even when the gate-controlled dot level $\e_\text{dot}(V_g)$ is far above or far below $\e_F$. The calculated conductance $G$ of the dot exhibits an unambiguous signature for the Majorana end mode of the wire: in essence, an off-resonance dot [$\e_\text{dot}(V_g)\neq \e_F$], which should have G=0, shows instead a conductance $e^2/2h$ over a wide range of $V_g$, due to this leaked mode into the dot. Interestingly, this pinning effect only occurs when the dot level is coupled to a Majorana mode; ordinary fermionic modes in the wire simply split and broaden (if a continuum) the dot level. We discuss three experimental scenarios to probe the Majorana modes in wires via these leaked/pinned dot modes.
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