# FFLO-Phase in Quantum Liquids, Quantum Gases, and Nuclear Matter

## Workshop Report

The workshop was held at MPIPKS in Dresden from June 20 to June 24, 2016.

The discovery of the so-called Fulde-Ferrell-Larin-Ovchinnikov (FFLO) effect had its 50-year anniversary in 2014, and enjoys a renewed interest during the past decade in superconductivity, cold fermionic gases, as well as nuclear and quark matter. It describes the appearance of Cooper pairs with a finite center of mass momentum as a result of a spin polarization arising either from an externally applied magnetic field, from a spin imbalance, or from an internal exchange field. The appearance of such a state shows intriguing properties, as singlet-triplet mixtures, spatially inhomogeneous order parameters, and unconventional pairing.

The aim of this workshop was to bring together the communities working on FFLO effects in heavy-fermion systems, in organic superconductors, in superconductor-ferromagnet hybrid structures, in spin Peierls systems in magnetic fields, in cold atomic gases, and in nuclear matter. With the unifying theme of FFLO pairing states in such a diverse number of fields in physics a fruitful exchange between otherwise rather disjoint communities was possible.

The workshop started, after welcome words by Roderich Moessner, with short historical notes by Profs. Fulde and Ovchinnikov, who both were guests of honor, and an introductory presentation by Gertrud Zwicknagl. On Monday evening, a Colloquium was presented at the Festsaal Dülferstraße by Wilhelm Zwerger - a common event of TU Dresden, the MPIPKS, and all other physics-related institutions in Dresden. The large lecture hall was filled to the last seats, and the Colloquium was followed by a reception with lively discussions between the participants of the workshop and audience members from TU Dresden.

The workshop was special in the broad spectrum of topics it covered, with the FFLO mechanism as unifying theme. We had a number of high-level speakers in spin-imbalanced cold atomic gases (Zwerger, Zwierlein, Hu), in the fields of quantum chromodynamics (Mannarelli) and nuclear matter (Sedrakian), in layered organic superconductors (Uji, Brown, Mitrovic, Agosta), in superconductor-ferromagnet hybrid systems (Blamire, Annett, Melnikov, Linder), in quasi-one-dimensional systems (Brazovskii, Orso), and in strongly correlated superconductors (e.g. Mitrovic, Kasahara, Machida, Brison). Several interesting theoretical methods and predictions were discussed (e.g. Agterberg, Zhitomirsky), as well as exotic states of matter and applications, like odd-frequency pairing states (Fominov), $\phi$-junctions (Goldobin), topological superconductivity (Houzet), or antiferromagnetic superconductors (Bulaevskii).

We had two extended poster presentations on Tuesday and Thursday, and a spectrum of early-carrier participants and students. In addition we had presentations by early carrier speakers (e.g. Mazzone, Gukelberger, Croitoru), as well as involvement of students and younger scientists in the technical organization (Gronemann, Coniglio). There was also lively communication between junior and senior participants during the workshop excursion to the Baroque castle Moritzburg on Wednesday afternoon.

The scientific results of the conference in the broader sense include a higher awareness of similar methods and phenomena in fields describing as diverse systems as quark matter, nuclear matter, cold atomic gases, superconductors, hybrid structures, charge density wave order, and antiferromagnetic materials, and covering an extraordinary energy range from 10-9 to 109 Kelvin. The FFLO effect thus proved to have a great integrative power between scientific communities.

Apart of giving a broad overview over imbalanced Fermi systems in physics, the conference also accelerated the development of the field and was conducted in a highly inspiring atmosphere.

Several speakers and participants as well as guests of honor expressed their gratitude for the throughout high quality of the presentations, the broad range of topics brought together by a unifying theme, as well as the relaxed atmosphere during scientific discussions and poster sessions. We would like to add that MPIPKS and the workshop administrator Amy Wright excellently handled the organizational and other administrative formalities of the workshop.