This thesis focuses on thermoelectric properties of nano-scale devices based on quantum effects. These properties involve interesting fundamental physical phenomena and can also be used for practical applications, e.g., in optimising the heat waste problem in electronics.
This thesis focuses on thermoelectric properties of nano-scale devices based on quantum effects. These properties involve interesting fundamental physical phenomena and can also be used for practical applications, e.g., in optimising the heat waste problem in electronics.
Chapter 1 provides a general introduction to the topic and an outline of the thesis.
Chapter 2 contains a concise description of the theoretical concepts relevant to the study.
Chapter 3 describes the implementation of superconductor-normal metal-superconductor thermometry in electromigrated break junction architecture. In this chapter, we show how to create a thermopower device and how to perform thermometry measurements correctly.
Chapter 4 is dedicated to the detailed description of the double lock-in method that allows to simultaneously measure differential conductance and thermocurrent. We focus on the different aspects behind the technique including performing the experiments, processing the data and interpreting the results.
Chapter 5 describes the experimental investigation of the thermopower response of a di-radical all-organic molecule in a proximityinduced superconducting junction. We demonstrate how the system can be switched from the Kondo state to the Yu-SHiba-Rusinov regime, which is accompanied by a five-fold increase in the power factor.
Chapter 6 contains the description of the first single-molecule particle exchange heat engine and the process of fine-tuning it to find the optimal load value for maximum power output.
Chapter 7 describes the thermocurrent response of a CrSBr flake upon changes in the magnetic field and temperature. We demonstrate that spin-entropy plays a role and that the Seebeck coefficient is enhanced close to the phase transition point. We also show that at low temperatures the power factor of the device can be changed by 600% upon applying a magnetic field.
Chapter 8 concludes this thesis with a discussion of the results presented in the previous chapters, ideas on potential future follow-up experiments and on practical implications of the findings presented.
