Signatures of Majorana modes leaking into double quantum dot systems
I. Weymann1, P. Majek1, K.P. Wójcik2,3
1 Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
2 Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland
3 Institute of Physics, Maria Curie-Skłodowska University, Lublin, Poland
We analyze the spectral and transport properties of a strongly-correlated double quantum dot attached to metallic contacts and to a topological superconducting nanowire, hosting Majorana bound states. We show that, depending on the device geometry, the Majorana modes can leak into the both quantum dots, giving rise to fractional values of conductance and revealing a subtle interplay between the Kondo screening and the half-fermionic nature of Majorana quasiparticles. In particular, in the case when only one quantum dot is directly attached to metallic leads, the interference with the Majorana modes lifts the suppressed conductance due to the two-stage Kondo effect from zero to a fractional value of e2/2h. Moreover, the coupling to topological superconductor is also found to enhance the second-stage Kondo temperature. On the other hand, when both quantum dots are attached to external leads, we show that the presence of Majorana mode gives rise to unique features visible in the local density of states in the SU(4) Kondo regime. It also greatly modifies the gate voltage dependence of the linear conductance, leading to new fractional values of the conductance. Finally, we study the case when the leads are subject to a thermal gradient, focusing on the behavior of thermopower and revealing new sign changes in the temperature dependence of the Seebeck effect due to the presence of Majorana bound states.
[1] I. Weymann, K. P. Wójcik, P. Majek, Phys. Rev. B 101, 235404 (2020).
[2] P. Majek, I. Weymann, Phys. Rev. B 104, 085416 (2021).
[3] P. Majek, K. P. Wójcik, I. Weymann, Phys. Rev. B 105, 075418 (2022).
We acknowledge support from the National Science Centre in Poland through the Project No.2018/29/B/ST3/00937.