Kondo effect in a quantum dot side-coupled to a topological superconductor

Abstract

We investigate the dynamical and transport features of a Kondo dot side coupled to a topological superconductor (TS). The Majorana fermion states (MFSs) formed at the ends of the TS are found to be able to alter the Kondo physics profoundly: For an infinitely long wire where the MFSs do not overlap ( m = 0) a finite dot-MFS coupling ( m ) reduces the unitary-limit value of the linear conductance by exactly a factor 3/4 in the weak-coupling regime ( m < T K ), where T K is the Kondo temperature. In the strong-coupling regime ( m > T K ), on the other hand, the spin-split Kondo resonance takes place due to the MFS-induced Zeeman splitting, which is a genuine many-body effect of the strong Coulomb interaction and the topological superconductivity. We find that the original Kondo resonance is fully restored once the MFSs are strongly hybridized ( m > m ). This unusual interaction between the Kondo effect and the MFS can thus serve to detect the Majorana fermions unambiguously and quantify the degree of overlap between the MFSs in the TS.

Thermoelectrical detection of Majorana states

“…2(b)]. In all cases, as long as ζ = 0, the dot transmission at ω = 0 is always half fermionic [55,56]. As the Majorana overlap becomes finite (ε M = 0), T d (ω = 0) becomes unitary, as shown in Fig.…”

“…Both the electric and thermal conductances, G and K, depend strongly on ε d for finite ε M k B T b . Otherwise, in the ideal situation where ε M = 0, G and K are half fermionic and immune to ε d [55][56][57]. This important result serves us to detect the Majorana states in side-coupled dot nanowires systems.…”

“…However, this physical scenario can be dramatically altered by inserting a quantum dot in between the two normal contacts and side-coupled to the Majorana nanowire [see Fig. 1(b)] [54][55][56]. In this arrangement, the Seebeck coefficient can be tuned by gating the dot, i.e., S = S(ε d ) with ε d the dot level position.…”

Non-Kondo many-body physics in a Majorana-based Kondo type system

“…A Majorana mode may also be coupled to a quantum dot to explore the competition between Kondo and Majorana physics. [55][56][57][58] However, these works do not fully explore the potential of the Majorana modes as a novel interface between the topological superconductor and its environment.…”

Isolating Majorana fermions with finite Kitaev nanowires and temperature: the universality of the the zero-bias conductance

“…This demands manufacturing long KNWs to prevent the MBSs overlapping and the consequent ZBP quenching at very low temperatures, what is considered a hard experimental challenge [17][18][19][20][21][22][23][24][25][26] . In this work, we explore the quantum dot (QD)-Kitaev nanowire (KNW) hybrid setup [27][28][29][30][31][32][33][34][35] sketched in Fig. 1 based on the recent experimental advances achieved by Deng et al 26 in verifying the leakage of the MBS zeromode into the QD, which was first predicted theoretically in Ref.…”