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Superconductivity on the Verge
Organisers: Lara Benfatto, Andrea Caviglia, Antonio M. García-García, Jerome Lesueur , Pratap Raychaudhuri
The recent technological developments in the synthesis and characterization of superconducting materials in low dimensions has revealed intriguing similarities between strongly disordered films of materials like NbN, InOx or TiN, superconducting LaAlO3-SrTiO3 engineered hetero-structures, and artificial superconducting nanostructures. The open questions raised by the experimental and theoretical progresses made in the last 5 years in all these fields are often very similar: Is the survival of SC properties at strong disorder or low carriers a signature of localization of bosonic pairs? What controls the typical length scales over which local and global superconductivity is established? However, despite these analogies, the scientific communities involved in these apparently different classes of material remain substantially separated.
The main goal of this workshop was to bring together researchers working in the fields of strongly disordered superconductors, hetero-structures and artificial nanostructures with the twofold aim to establish the analogies and differences between these areas and to promote a cross-fertilization of ideas that can bring new perspectives on the research agenda for the future.
The balance after the five days workshop is extremely positive. We can report that the workshop has been very successful in shaping and moving forward this emerging research field. We based this assessment on the following indicators:
1- The workshop structure was based on a topic session followed by a discussion session on the questions raised during the talks, to stimulate cross-fertilization among researchers with different backgrounds. This structure was definitively very efficient, since all talks and discussions were well attended. Multitude of questions and lively exchanges among participants, even between researchers with relatively different backgrounds, were a constant across the workshop.
2- Each talk was blogged by a participant, not necessarily in the same field as the speaker. Even though it is a relatively time consuming task, we found all participants willing to blog a colleague. We were pleasantly surprised by the high quality of the blogs and the interesting questions posed by some of the bloggers. The blogs are linked to the workshop webpage.
3- According to informal discussions, the workshop helped to establish multiple collaborations and to open new research lines for many of the participants.
Some of the results presented in the workshop attracted an unusual level of interest and discussion:
1. The observation of a “strange” metallic phase, characterized by a plateau in the resistivity, observed in the low temperature limit of superconducting STO/LAO heterostructures. Is this phase universal? What is its physical origin?
2. The observation of high Tc (Tc >100K) superconductivity in one-layer FeSe on STO. What is the mechanism of superconductivity? Is it possible to find this novel form of enginnered high Tc superconductivity in other materials? Is it a Kosterlitz-Thouless transition?
3. The conditions for the observation of the Higgs mode in disordered superconductors. Is the recent claimed experimental observation conclusive?
4. The observation of novel quantum phase transitions in disordered STO/LAO heterostructures. Are these phase transitions universal and therefore observable in other materials? Is it necessary further experimental and theoretical progress for a quantitative description of these transitions?
There was consensus among participants that advances in these problems would set the agenda of this emerging field in the coming years.
As a final remark, we can say that all participants gave us spontaneously a very positive feedback on the choice of this workshop structure, and many of them found this “one of the most interesting and lively workshop” they had attended in the last years. On this respect, the selection of participants was crucial to create the right conditions for exchanging ideas. In addition, our decision to have 30% of female speakers (i.e. a factor of 3 larger than what happens usually in these communities) was positively appreciated by all participants. We would like also to report to Lorentz Center organization the suggestion made by some participants concerning the possibility for the workshop attendees to access to some childcare facilities during their stay. Having a larger percentage of female participants and helping them to reconcile these activities with the child-care constitute to us two important steps forward to create better conditions for the presence of female researchers in hard sciences.