Strongly correlated thermoelectric transport beyond linear response

We investigate nonlinear thermoelectric transport through quantum impurity systems with strong on-site interactions. We show that the steady-state transport through interacting quantum impurities in contact with electron reservoirs at significantly different temperatures can be captured by an effective-equilibrium density matrix, expressed compactly in terms of the Lippmann-Schwinger operators of the system. In addition, the reservoirs can be maintained at arbitrary chemical potentials. The interplay between the temperature gradient and bias voltage gives rise to a nontrivial breaking of particle-hole symmetry in the strongly correlated regime, manifest in the Abrikosov-Suhl localized electron resonance. This purely many-body effect, which is in agreement with experimental results, is beyond the purview of mean-field arguments.

Figure 1

Plot of the spectral function of the dot illustrating particle-hole symmetry breaking due to the interplay of $\Delta T$ and $\Phi$. We have used the units $\Gamma =1$ and set $T_{-1}=0$, $\Phi =0.4$, and $U=3\pi$. Raising the $T_1$ corresponds to increasing both $\overline{T}$ and $\Delta T$, and is seen to suppress the Abrikosov-Suhl resonance as well as amplify the extent of the particle-hole symmetry breaking as evident in the inset.

Figure 2

Effect of $\Delta T$ on the differential conductance when $\Delta =0.4$. We have used the units $\Gamma =1$ and taken $U=3\pi$. The inset on right shows the corresponding spectral function when $\Phi =0$ and the current in the neighborhood of zero bias is shown in the left inset.