Superflow Stability: Exploring Dynamics of Inhomogeneous Superfluids
This project studies inhomogeneous superfluids dynamics using ultracold atomic gases.
It investigates how excitations, interfaces, spin imbalance and interactions shape superfluids dynamics.
Findings will advance understanding of superfluid behavior, powering future quantum devices and simulators
of neutron stars, superfluid helium and superconductors.
PI: Klejdja Xhani
Project Duration: 01/05/2026-30/04/2031
The Project
Inhomogeneous superfluids — systems in which the order parameter varies in space rather than remaining uniform —
are central to understanding a remarkably diverse range of physical systems, from superconductors and superfluid helium
to the neutron-rich interiors of neutron stars. This project SANDI investigates how pair-breaking, thermal excitations,
and spin imbalance drive these spatial and temporal variations, giving rise to rich dynamical behavior that remains largely unexplored.
Ultracold atomic gases provide an exceptionally clean and controllable setting for this study. By tuning interactions,
it is possible to study from a strongly interacting unitary Fermi gas, a weakly interacting BCS-like superfluid,
to a molecular Bose-Einstein condensate. The project combines two complementary time-dependent theoretical frameworks
— a density-functional approach for fermionic superfluids and a kinetic description for finite-temperature
Bose-Einstein condensates — to follow how these systems evolve out of equilibrium and to search for universal
dynamical features across fermionic and bosonic regimes.
The research focuses on two main themes. The first explores the dynamics of coupled ring-shaped superfluids,
with particular attention to interface instabilities, vortex nucleation, vortex transport and superfluid tunneling
processes analogous to the Josephson effect. The second examines how persistent currents and vortices evolve under
spin imbalance, with the goal of identifying dynamical signatures of long-predicted exotic phases such as FFLO-like states.
By clarifying the dynamics of inhomogeneous superfluids under realistic conditions, the project aims to inform the
understanding of time-dependent phenomena in superconductors, superfluid helium, and neutron stars, and to support
the development of future atomtronic devices and quantum simulators.
Project Duration
01/05/2026-30/04/2031
The Team
- Klejdja Xhani – Principal Investigator
Publications
Coming soon.
Master Thesis
Vortex Pinning and Unpinning in Fermionic Superfluids
In fermionic superfluids, the vortex core differs fundamentally from that in bosonic condensates.
While vortex cores in Bose–Einstein condensates are empty at zero temperature, at strongly interacting
unitary Fermi gases (UFG) and BCS regimes vortices host localized quasiparticles occupying discrete
Caroli–de Gennes–Matricon levels. These bound states give rise to a finite core density and enhanced
dissipation in vortex motion, which becomes stronger toward the BCS limit.
This microscopic structure strongly influences vortex interactions with external potentials, impurities, and boundaries,
making the mechanisms of vortex pinning and unpinning an important open question in ultracold Fermi-gas theory.
Clarifying this link is essential for understanding dissipation, vortex dynamics, and quantum turbulence in systems
from ultracold gases to neutron star interiors.
The thesis will involve theoretical and numerical simulations studies, employing Bogoliubov–de Gennes and
time-dependent density functional simulations.
Josephson Effects and Atomtronic Circuits in Fermionic Superfluids
Atomtronic circuits using bosonic superfluids have realized stable persistent currents and Josephson effects via ring
geometries with controllable critical current and phase slips events by controlling number of Josephson junctions,
as demonstrated in theoretical studies of Josephson junction atomtronic necklaces.
Fermionic superfluids exhibit Josephson effects across the BEC-BCS crossover, but atomtronic ring circuits with
multiple junctions remain unexplored. This thesis will model fermionic Josephson junctions in ring networks,
examining how pair-breaking effects—linked to superflow exceeding the pair-breaking velocity—govern
current-phase relations, persistent current stability, and dissipation.
Conferences
22-26 June 2026
SCALES 1st General Meeting - Superfluid Condensates in Astrophysics and Laboratory Experiments
Physics Department, University of Coimbra
News
03 July 2026
RPMBT23 Conference in Milan
14 to 18 September 2026: The 23rd International Conference on Recent Progress in Many-Body Theories (RPMBT23),
which will take place in Milan, Italy.
RPMBT23 will bring together researchers working across a broad range of topics, from quantum field theory to quantum fluids,
providing a valuable forum for discussing recent advances in many-body physics, sharing new results, and fostering scientific
exchange within the international community.
Although the official submission deadline has passed, there is still the possibility to submit an abstract for a poster presentation.
For more information, please visit the official conference website:
RPMBT23.
03 July 2026
School on Quantum Simulation and Quantum Computing
9-11 September 2026: The School on Quantum Simulation and Quantum Computing in Milan, Italy.
The school is dedicated to quantum simulation as a tool for studying real-time many-body dynamics, with a focus on problems
that are intrinsically difficult to address using classical computing methods. It is intended for Master’s students,
PhD students, and early-stage researchers with a background in quantum many-body physics.
A key feature of the school is its practical component, which will provide participants with access to real quantum hardware.
Selected quantum simulation protocols will be run on the IBM Quantum platform and on the Lagrange IQM Spark quantum computer in Turin.
Preparatory material is available for participants in advance, and registration remains open until 15 July 2026.
More information can be found on the school page:
School on Quantum Simulation.
