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Strongly Disordered Superconductors and Electronic Segregation
1; Description and Aim: Apart from the interesting fundamental problem of competition between strong localization and superconductivity, disordered superconductors are interesting materials to study quantum phase slip processes as well as for use in the detection of faint astronomical signals using compact superconducting resonators. The focus of the workshop was on strongly disordered superconductors in which it is becoming clear, theoretically and experimentally, that even in cases where the materials are “uniformly” disordered, electronic properties become inhomogeneous. The workshop brought together a cross-section of experimentalists, engineering-physicists and theorists to discuss the latest results and to identify the research-challenges ahead. The aim was to let these communities communicate and to identify problems that would be solvable and useful.
2; Tangible outcome:
a; The relatively closed community of people interested in the complexity of strongly disordered superconductors discovered that there are communities emerging that want to use these materials in specific experiments or for detectors. A very interesting surprise of that nature was that on the first day, fresh data (one week old) were reported on quantum phase slips observed in InOx microbridges (Oleg Astafiev).
b; A rethinking of the classification of the systems studied occurred. Traditionally separated in granular and homogeneously disordered the community became aware of the fact that the latter will also become granular on an electronic level and that a strict distinction is not intellectually productive
c; In anticipation of the workshop several calculations were performed to answer questions, which had come into focus because of the different communities that were coming together.
d; Several arrangements were made to exchange samples
e; An in principle agreement was reached between European groups to apply for joint funding through an ITN in the Marie Curie program.
3; Expected scientific breakthroughs: It is to be expected that the ideas worked out to use these materials for quantum phase slip processes will lead to more experiments of this kind, as well as a thorough reflection on why the dissipation leading to decoherence is much lower. It is supposed to be due to the fact that the normal state is also ‘gapped’. It is expected that deviations from standard BCS electrodynamics will also be studied thoroughly.
4; Surprising elements:
a; The power of local tunneling spectroscopy to study the properties of disordered films
b; The usefulness of these materials in various areas of science
c; The needed fundamental studies to make further progress in understanding and use of these materials.
5; Format of the workshop:
Despite the fact that there was ample time created for discussions that were connected to each presentation, there was a wish that more time would have been available. Almost all participants stayed until the last day. It was very important has been that we included 4 discussion sessions and asked per session to have 2 discussion leaders, giving them focused questions as a guideline. It was initially met with some skepticism by the discussion leaders, but in practice all sessions were very lively.
A 2nd very important addition was an initiative by Peter Armitage to create a conference blog (http://strongdisordersuperconductors.blogspot.com/). Participants were asked to summarize talks and the discussion sessions, which was faithfully done by most. These summaries were posted and the website for the workshop of the LC referred to this site. It had 2 effects. The participants were actively involved in making the workshop a success by writing the piece and checking with the presenters the perceptions. In addition, while the blogspot was consulted 400 times during the workshop the blogspot continued to be used after the workshop having about 1100 hits a month later. It is the organizer’s impression that this is due to the fact that each participant, after being back in his or her own community, uses it as a resource to refer others to.
6; Other comments
Everybody was very pleased with the accommodations and the staff of the LC. From the organizer’s point of view there is room for improvement with respect to the path from application, getting feedback from the board, as communicated in writing and explained by the staff of the LC, rewriting the proposal and the actual experienced success of the workshop. Part of the work of the organizers is to mobilize participants for a particular format, while most of them have to pay their own costs. Intended participants have to become convinced that a workshop like this is different and special. Since we had also ICAM support it was brought to our intention that they demand application of the “Hans Frauenfelder rules for a successful workshop”. In retrospect it would have been helpful if the staff of the Lorentz-center would adopt a similar set of rules, which can be used for reference in inviting participants and setting up the program.