Nonequilibrium and transport in proximity of superconductors

Mesoscopic physics studies systems that are larger than atoms but small enough to exhibit quantum coherent effects. Thanks to improved fabrication techniques, study of superconductivity and its effect on contacted materials in tailored micrometer-scale mesoscopic structures has become possible in the recent decades. Electron transport, non-equilibrium response, thermoelectricity, and fluctuations in such devices have attained significant interest. Thermoelectric effects in particular are one of the least understood aspects of superconductivity. Quantitative understanding of the observations in the mesoscopic regime has turned out to require quantum-mechanical models. Devices based on mesoscopic superconductivity have also technological applications, in addition to being of primary scientific interest. This thesis discusses theoretical studies on thermoelectric and out-of-equilibrium effects in superconducting proximity structures. Green function methods are applied for computing the thermoelectric and nonequilibrium response of mesoscopic structures to external driving. The results explain several features observed in experiments, and clarify one origin of thermoelectricity in the studied systems. Electrical fluctuations in mesoscopic structures are also discussed, and a device for characterizing the statistics and spectrum of the fluctuations is proposed. This mesoscopic on-chip detector is based on a superconducting Josephson junction in the Coulomb blockade regime. It is expected to bypass problems in conventional measurements of higher-order statistics of noise. That the detector can be manufactured close to the measured mesoscopic noise source could also enable studies of quantum properties in the higher-order statistics of the fluctuations.

Grantor dc:publisher

Teknillinen korkeakoulu

Year dc:date.issued

2009

Author dc:creator

• Virtanen, Pauli

Contributors dc:contributor

• Aalto-yliopisto
• Aalto University

Language dc:language.iso

en

Repository record dc:identifier.uri

https://aaltodoc.aalto.fi/handle/123456789/4657

OAI record oai:identifier

https://aaltodoc.aalto.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aaaltodoc.aalto.fi%3A123456789%2F4657