We investigate the linear thermoelectric response of an interacting quantum dot side-coupled by one of two Majorana fermions (MFs) formed at the ends of a topological superconducting wire. We employ the numerical renormalization group technique to obtain the thermoelectrical conductance $L$ as well as the electrical conductance $G$ when the background temperature $T$ and the dot gate are tuned. We distinguish two transport regimes in which $L$ displays different features: the weak- $(\Gamma_{ m} < T_{ K})$ and strong-coupling $(\Gamma_{ m} > T_{ K})$ regimes, where $\Gamma_{ m}$ and $T_{ K}$ are the Majorana-dot coupling and the Kondo temperature, respectively. For an ideal (infinitely long) nanowire where the Majorana end states do not overlap $(\epsilon_{ m} = 0)$, the thermoelectrical conductance $L$ in the weak-coupling regime exhibits a peak at $T \sim \Gamma_{ m}$. This peak is ascribed to the anti-Fano resonance between the asymmetric Kondo resonance and the zero-energy MF mode. Interestingly, in the strong-coupling regime, the Kondo-induced peak in $L$ is shifted due to the MF-induced Zeeman splitting in the dot. For finite but small $\epsilon_{ m} > 0$, the interference between two MFs restores the Kondo effect in the dot in a smaller energy scale $\Gamma^{ \prime}_{ m}$ and gives rise to an additional peak in $L$ at $T \sim \Gamma^{ \prime}_{ m}$, whose sign is opposite to that at $T\sim\Gamma_{ m}$. In the strong-coupling regime this additional peak can cause a non-monotonic behavior of $L$ with respect to the dot gate. Finally, we examine the case in which an ordinary spin-polarized fermion is coupled to the dot and identify the fingerprint of MFs by comparing two cases.
Categories: cond-mat.mes-hall