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 ${\varepsilon }_F$ of the leads. Surprisingly, this resonance pinning, resembling, in this sense, a “Kondo resonance,” occurs even when the gate-controlled dot level ${\varepsilon }_{\mathrm{dot}}\left(V_g\right)$ is far above or far below ${\varepsilon }_F$. 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 [${\varepsilon }_{\mathrm{dot}}\left(V_g\right)\ne {\varepsilon }_F$], which should have $G=0$, shows, instead, a conductance $e^2/2h$ over a wide range of $V_g$ due to this pinned dot mode. Interestingly, this pinning effect only occurs when the dot level is coupled to a Majorana mode; ordinary fermionic modes (e.g., disorder) in the wire simply split and broaden (if a continuum) the dot level. We discuss experimental scenarios to probe Majorana modes in wires via these leaked/pinned dot modes.

• Received 15 August 2013
• Revised 10 April 2014

DOI:https://doi.org/10.1103/PhysRevB.89.165314