Wykład zatytułowany Quantum thermodynamics with a single superconducting vortex wygłosi dr hab. inż. Maciej Zgirski (Instytut Fizyki Polskiej Akademii Nauk w Warszawie).
Superconducting vortices are topological objects appearing naturally in type II superconductors as an energetic compromise between Meissner and normal states. First predicted by Abrikosov back in 1950s, nowadays they are widely studied both in low and high temperature superconductors forming its own research field referred to in the literature as the vortex matter. Although fundamental investigations are very rich and spectacular, vortex physics has not resulted in broad applications. The number of reports which would take advantage of the vortex to present new functionalities is rather small. Meanwhile superconducting electronics is developing rapidly holding promise for building quantum computer based on superconducting qubits and involving demonstration of novel-concept quantum sensors and devices. It is thus timely to harness vortices to our advantage, to increase the portfolio of desired functionalities provided by the superconducting electronics.
We present a very simple all-superconducting device consisting of a nanosquare(s) and an adjacent nanobridge . We develop the electrical protocol allowing us to trap on demand the various superconducting vortex configuration in the field-cooled nanosquare, and test the trapped configurations by measuring the switching current of a Dayem nanobridge. Our measurements exhibit unprecedented precision and ability to detect the first and successive vortex entries into all fabricated traps, from few hundred nm to 2 μm in size. Using the method of fast time-resolving switching thermometry developed in the Institute of Physics over last years [2-5], we have measured the heat and subsequent thermal relaxation of the nanostructure arising from the expulsion of a single magnetic field vortex with an electric current pulse. This demonstration is a first calorimetric detection of the dissipation in a superconductor due to a single moving vortex.
Additionally, we have performed experimental studies of hot electron diffusion in the presence of superconducting vortices. We obtain suppression of the diffusion signal due to existence of a single vortex trapped in the box on the way between the source of hot electrons and the detecting nanobridge. In other words, we can see the single vortex by the influence it exerts on the flux of diffusing quasiparticles.
Our device allows to treat a superconducting vortex as a macroscopic, albeit quantized “particle”, which can be created and annihilated with pulses of electrical current. An ease of integration and simplicity make our design a convenient platform for studying dynamics of vortices in strongly confining geometries and demonstrating novel-concept logical devices.