Heat Diodes Made of Quantum-Dot Nanowires

We report theoretical studies of nonlinear electron heat transport in a nanowire embedded with quantum dots connected to metallic electrodes. It is demonstrated that the nonlinear Seebeck effect can lead to significant electron heat rectification for such a wire with staircase-like energy levels. The asymmetrical alignment of energy levels of such quantum-dot nanowires (QDNWs) can be controlled to allow resonant electron transport under forward temperature bias, while they are in off-resonant regime under backward bias. Once taking into account the presence of phonon heat flows, the efficiency of electron heat rectification is suppressed. However, the heat rectification ratio of QDNWs can still reach an impressive value around 10 at temperature as high as 30K for Si/Ge QDNWs with width around 3 nm, when the multi-valley degeneracy of Si QDs is taken into account.