https://doi.org/10.1140/epjb/e2015-60200-9
Regular Article
Thermoelectric effect in the Kondo dot side-coupled to a Majorana mode
1 Department of PhysicsKorea
University, 136-701 Seoul, Korea
2 Institut de Física Interdisciplinària
i Sistemes Complexos IFISC (UIB-CSIC), 07122
Palma de Mallorca,
Spain
3 School of Physics, Korea Institute
for Advanced Study, 130-722
Seoul,
Korea
4 Department of Applied Physics and
Institute of Natural Sciences, College of Applied Science, Kyung Hee University,
446-701
Yongin,
Korea
a
e-mail: minchul.lee@khu.ac.kr
Received:
12
March
2015
Received in final form:
7
May
2015
Published online:
10
June
2015
We investigate the linear thermoelectric response of an interacting quantum dot side-coupled by one of two Majorana modes hosted by a topological superconducting wire. We employ the numerical renormalization group technique to obtain the thermoelectrical conductance L in the Kondo regime while the background temperature T, the Majorana-dot coupling Γm, and the overlap ϵm between the two Majorana modes are tuned. We distinguish two transport regimes in which L displays different features: the weak- (Γm<TK) and strong-coupling (Γm>TK) regimes, where TK is the Kondo temperature. For an infinitely long nanowire where the Majorana modes do not overlap (ϵm = 0), the thermoelectrical conductance in the weak-coupling regime exhibits a peak at T ~ Γm<TK. This peak is ascribed to the anti-Fano resonance between the asymmetric Kondo resonance and the zero-energy Majorana bound state. In the strong-coupling regime, on the other hand, the Kondo-induced peak in L is affected by the induced Zeeman splitting in the dot. For finite but small overlap (0 <ϵm<Γm), the interference between the two Majorana modes restores the Kondo effect in a smaller energy scale Γ′m and gives rise to an additional peak in Γ ~ Γ′m, whose sign is opposite to that at T ~ Γm. In the strong-coupling regime this additional peak can cause a non-monotonic behavior of L with respect to the dot gate. Finally, in order to identify the fingerprint of Majorana physics, we compare the Majorana case with its counterpart in which the Majorana bound states are replaced by a (spin-polarized) ordinary bound state and find that the thermoelectric features for finite ϵm are the genuine effect of the Majorana physics.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2015