Heat Transport from On-demand Single-Electron Sources

Doktorsavhandling, 2019

The controlled injection of quantized charge excitations from single-electron emitters into nanoscopic conductors sets the basis for many important applications ranging from metrology to the emerging field of quantum optics with electrons. Successful implementation of these applications relies not only on achieving control on the precision of the particle emission, but also on the energetic properties of the injected particles. These fundamental properties are reflected in transport observables such as time-resolved charge and energy current, as well as the spectral, i.e. energy-resolved current, or the zero-frequency correlators of charge and energy currents, thereby providing a tool for transport spectroscopy.

This thesis deals with two important aspects of the characterization of different time-dependently driven single-electron sources (SES): it provides (i) a detailed analysis of the aforementioned observables and (ii) proposals for the readout of such transport properties. First, we analyze in detail the transport observables in three different SESs. The SESs differ by the characteristics of the applied time-dependent driving voltage and by the degree of particle confinement in the driven conductor; their common feature is that pulses of quantized charge are produced going along with a minimal excitation of the Fermi sea. We point out the impact of the device design and of tunable external pa- rameters, such as temperature, on the transport observables. Second, we the- oretically propose ways to experimentally access the transport observables. Charge transport observables are standardly detected for different kinds of sources. In contrast, energy transport–particularly energy-current noise– is more difficult to access experimentally. We propose a setup for the detection of fluctuating charge and energy currents, as well as their correlations, generated by a SES, via reading out frequency-dependent electrochemical- potential and temperature fluctuations in a probe contact. Furthermore, in a second proposal, we investigate how to access the spectral current, giving access to the particles’ energy distribution, in an energy-selective detector setup. More specifically, we propose to readout modifications of thermoelectric response coefficients due to the time-dependent driving as a measure of the spectral current. However, importantly, this type of setup also opens completely novel routes: we find that SESs can be used as probes to sense until now unexplored quantum screening effects in thermoelectric transport.