Faculty @ Chalmers University, Sweden

Monday June 27 – 8.00 BST

Heat and charge currents across a QPC: opportunities for thermoelectrics and readout of screening effects

Quantum point contacts have a prominent role in electronic devices and act as beam splitters and energy filters. They are therefore simple examples for thermoelectric mesoscopic devices, where they were shown to maximise the possible power output. In this talk, I will present some of their properties for thermoelectric steady state heat engines and hot-carrier photovoltaics. In particular, I will show, how QPC-based thermoelectric heat engines perform in terms of precision, demonstrating a novel constraint of the “thermodynamic uncertainty relation” in the linear response regime of an operating engine [1]. I will furthermore show how the efficiency of energy conversion is influenced when the energy distribution of the heat source is described by a non thermal state as it is the case for example in hot-carrier solar cells [2]. 

When the QPC based thermoelectric device is operated at large voltage and/or temperature biases, the transmission of the QPC is modified due to screening effects. These modifications, which can have electrostatic as well as quantum origin, strongly depend on different conductor properties and are typically hard to access from experiments. In the second part of my talk, I will present a proposal how to readout these screening effects by exploiting tunable corrections to the thermoelectric linear-response coefficients, which occur when an additional ac signal is applied via a third terminal [3]. 

[1] S. Kheradsoud, N. Dashti, M. Misiorny, P. P. Potts, J. Splettstoesser, P. Samuelsson: Entropy 21, 777 (2019). 

[2] L. Tesser. R. S. Whitney, J. Splettstoesser, in preparation. 

[3] N. Dashti, M. Acciai, S. Kheradsoud, M. Misiorny, P. Samuelsson, J. Splettstoesser: Phys. Rev. Lett. 127, 246802 (2021).

Categories: Talks Monday June 27