Advancing the methodologies for the realization of thermoelectric circuits in van der Waals high temperature twisted cuprate heterostructures.

• Applicant: Privatdozent Nicola Poccia, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512734967

Superconducting and topological states are among the most fascinating quantum phenomena in nature. The entanglement of these two states into a topological superconducting state will give rise to even more exotic quantum phenomena, such as time reversal breaking symmetry states. Recently, a new class of topological superconductors, that can sustain temperature up to the boiling nitrogen point, has been predicted in twisted Bi2Sr2Can-1CunO2n+4 van der Waals heterostructures. Although it is generally preferred to work with a single material because interfacing two materials may suffer from the interfacial reaction and lattice mismatch between a superconducting and a topological material, recent experimental methodological advances have enabled the realization of the interfaces between Bi2Sr2Can-1CunO2n+4 van der Waals twisted heterostructures free from detrimental defects, oxygen loss, and lattice reconstruction. Last year, there has indeed been some experimental evidence that a topological state may be present in these twisted heterostructures, even though a conclusive proof has not yet been found. Thermal measurements are therefore necessary since they have been shown to be a powerful tool for detecting topological states in superconductors. However, the circuit realization for a thermal measurement is complex due to the fragility of the Bi2Sr2Can-1CunO2n+4 van der Waals twisted heterostructures. Here, we propose to optimize a novel methodology in order to realize thermal circuits using nanomembrane via contacts. We will apply this technique for realizing Seebeck and Nernst measurements. We will calibrate our measurements based on the heat losses through a thermal insulating substrate, and we will determine if a time reversal symmetry state does actually exist at the predicted magic angles.

• DFG Programme: Research Grants