Effects of correlated hopping on thermoelectric response of a quantum dot strongly coupled to ferromagnetic leads

Abstract

We theoretically investigate the impact of correlated hopping on thermoelectric transport through a quantum dot coupled to ferromagnetic leads. Using the accurate numerical renormalization group method, we analyze the transport characteristics, focusing on the interplay between electronic correlations, spin-dependent transport processes, and thermoelectric response. We calculate the electrical conductance and thermopower as functions of the dot energy level, lead polarization, and the amplitude of correlated hopping. Moreover, we analyze the effect of competing correlations on the Kondo resonance and discuss the asymmetry of conductance peaks under the influence of the exchange field. We demonstrate that the presence of correlated hopping is responsible for asymmetric spin-dependent transport characteristics. Our results provide valuable insight into how correlated hopping affects spin-dependent transport and thermoelectric efficiency in quantum dot systems with ferromagnetic contacts.

Figures (7)

• Figure 1: Schematic of the considered quantum dot system with Coulomb interaction $U$ and dot level energy $\varepsilon$. The central part is connected to two ferromagnetic leads with coupling strength $\Gamma^\sigma_{L/R}$, for the left and right lead. There is a temperature gradient $\delta T$ and a small voltage gradient $\delta V_\sigma$ applied symmetrically to the system.
• Figure 2: The temperature dependence of the linear conductance $G$ for different values of the level position $\varepsilon$, as indicated in the legend. (a)-(h) present the results for different values of the correlated hopping parameter $x$, as indicated in the figure. The parameters are: $U=0.1D$, $\Gamma/U=0.1$ and $p=0.5$, where $D$ denotes the band halfwidth, which is used as energy unit.
• Figure 3: The temperature and energy level dependence of the linear conductance $G$ (upper row) and thermopower $S$ (lower row). The first column (a,e) shows the results in the absence of correlated hopping, while (b,f) present results for $x=0.1$, (c,g) show results for $x=0.3$, and (d,h) display results for $x=0.5$. The other parameters are the same as in Fig. \ref{['fig:fig2']}.
• Figure 4: The linear conductance $G$ as a function of the level position $\varepsilon/U$ for different values of the spin polarization $p$, as indicated. (a)-(f) present the results for selected values of the correlated hopping parameter $x$. In calculations we assumed $T/U=10^{-5}$, while other parameters are the same as in Fig. \ref{['fig:fig2']}.
• Figure 5: The linear conductance $G$ as a function of the level position $\varepsilon/U$ for different values of the spin polarization $p$, as indicated. (a)-(f) present the results for selected values of the correlated hopping parameter $x$. In calculations we assumed $T/U=10^{-2}$, while other parameters are the same as in Fig. \ref{['fig:fig2']}.