Publications

@phdthesis{Ryan2025,

title = {Transport Studies of Superconductors for Quantum Applications},

author = {Kevin Michael Ryan},

url = {http://www.nano.northwestern.edu/wp-content/uploads/2025/12/KMRyan_Thesis.pdf},

year  = {2025},

date = {2025-12-02},

urldate = {2025-12-02},

abstract = {In the emerging field of quantum technology, superconducting devices serve many roles and are today the most widely adopted basis for quantum computation. This is because ideally behaved superconductors obey macroscopic quantum phenomena which are relatively easy to manipulate.  However, in the laboratory things are almost never ideal, and the superconducting quantum devices which are hoped to someday yield fully fault tolerant quantum computers are in fact, quite faulty. Chief among their most pressing issues are excitations of the superconductor itself out of its many-body ground state, and other stray defects which can arise during construction of these devices. These issues, known colloquially as quasiparticle poisoning and two-level systems respectively, continue to be the subject of considerable study and will require extensive and detailed examinations if we are going to someday obtain truly competitive quantum computers. 



With this in mind, in this thesis we present studies into both quasiparticles and material defects in superconductors. By taking a transport approach to process development, we have explored the phenomenology of both conventionally prepared superconducting films and those produced via emerging techniques, so as to develop metrics for comparing superconducting devices. Via corroboration with material investigations, we have established compelling connections between inhomogeneity and transport properties with may be important in future developments. In parallel, we explore quasiparticle dynamics in the low temperature regime to better establish how these excitations behave collectively and shed new light on their fundamental behaviors. Such non-equilibrium transport studies of superconductors allow for rich, spectroscopic examination of quasiparticle interactions and may ultimately allow us to answer open questions on both the origin and mitigation of quasiparticle poisoning.},

keywords = {charge imbalance, Superconductivity},

pubstate = {published},

tppubtype = {phdthesis}

}

@phdthesis{Cadden-Zimansky2008,

title = {Nonlocal Coherence in Normal Metal-Superconductor Nanostructures},

author = {Paul Cadden-Zimansky},

url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/C-Z-Thesis-Final.pdf},

year  = {2008},

date = {2008-12-01},

keywords = {Andreev reflection, charge imbalance, crossed andreev reflection, Mesoscopic quantum transport, nanomagnets, phase coherence, Proximity effect, Superconductivity},

pubstate = {published},

tppubtype = {phdthesis}

}

@phdthesis{Jiang2005,

title = {Thermal Transport Near the Normal-Metal/Superconductor Interface in Mesoscopic Devices},

author = {Zhigang Jiang},

url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/JiangThesis.pdf},

year  = {2005},

date = {2005-06-01},

keywords = {Andreev reflection, charge imbalance, Mesoscopic quantum transport, phase coherence, Proximity effect, Superconductivity},

pubstate = {published},

tppubtype = {phdthesis}

}

@phdthesis{Aumentado2000,

title = {Nonequilibrium and Quantum Transport Phenomena in Mesoscopic Ferromagnet/Superconductor Heterostructures},

author = {José Aumentado},

url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/AumentadoThesis.pdf},

year  = {2000},

date = {2000-12-01},

keywords = {AMR, Andreev reflection, charge imbalance, crossed andreev reflection, Magnetism, Mesoscopic quantum transport, phase coherence, Proximity effect, spin transport},

pubstate = {published},

tppubtype = {phdthesis}

}

@phdthesis{Chien1998,

title = {Transport Phenomena Near The Normal-Metal/Superconducting Interface In Mesoscopic Devices},

author = {Chen-Jung Chien},

url = {http://www.nano.northwestern.edu/wp-content/uploads/2017/09/ChienThesis.pdf},

year  = {1998},

date = {1998-12-01},

keywords = {Andreev reflection, charge imbalance, Mesoscopic quantum transport, phase coherence, Proximity effect},

pubstate = {published},

tppubtype = {phdthesis}

}