The poster session will take place on Wednesday, 6th at 17:50. Participants who intend to present a poster should be reminded that no printing service is available at the conference venue and that the maximum size for the posters is 2 m x 1 m.
1 – Leandro Alvares Machado
Institute of physics of São Carlos
Excitation of Bose-Einstein condensates with temporal resolution in separate zones
Our research focuses on a BEC sample confined in a harmonic oscillator when is externally excited by an oscillatory magnetic field. While our group has previously studied these systems using a single pulse excitation, we now aim to study separate zones excitation, inspired by the Ramsey’s experiment. Our goal is to understand the coherence persistence of strongly excited BEC samples as a consequence of interference from a fragmented BEC. Through computer simulations and theoretical models, we aim to reproduce the experiments currently being carried out to study how an external signal can select specific paths in the route of turbulence.
2 – Alice Bellettini
Politecnico di Torino
Relative dynamics of quantum vortices and massive cores in binary BECs
We study vortices with massive cores in mixtures of BECs. We introduce a point-vortex model where quantum vortices in the majority species are coupled to their core masses, i.e. local peaks of the minority species. The point-like dynamics is obtained via a variational approach. We also validate our analytical results via the simulation of coupled Gross-Pitaevskii equations. Our new model brings to a more articulated normal mode analysis, and improves the previous model thanks to the dependency of the small oscillations on the coupling parameter. Also, we confirm that there is no significant vortex-core relative motion.
3 – Matteo Caldara
Scuola Internazionale Superiore di Studi Avanzati (SISSA)
Dynamics of massive superfluid vortices on a planar annulus
We analyze an immiscible binary mixture of Bose-Einstein condensates loaded in a planar rotating annulus where two-dimensional point vortices in one species host the atoms of the other species, that play the role of a massive core. The presence of a finite mass alters dramatically the vortex dynamics, since the particles trapped in the vortex core experience an effective gauge field provided by the surrounding superfluid component. The density-dependent effective magnetic field affects the frequency of uniform precession and leads to the onset of a cyclotron motion, which for large mass eventually becomes unstable. The results from the fully analytical massive point-vortex model are benchmarked against the numerical solution of coupled two-component GP equations. The analysis is then extended to a symmetric vortex necklace inside the annulus.
4 – Sian Cardoso Barbosa
University of Kaiserslautern-Landau
Tunable diffusion properties of spin-polarized Fermi gases in time-dependent disorder
Transport through disorder has been actively studied for the last decades. The majority of these studies, e.g. of Anderson localization, assume a static disorder potential. However, it seems natural to investigate the influence of time-dependent disorder on transport properties. I will present the results of our experimental investigation of the dynamics of ultracold, spin-polarized fermionic lithium atoms when exposed to an optical speckle potential that can be frozen or continuously varying in both space and time. We observe a strong dependence of the system’s diffusion exponent on the disorder’s rate of change, resulting in a crossover from localization to superdiffusion.
5 – Eloisa Cuestas
Okinawa Institute of Science and Technology
Making statistics work: a quantum engine in the BEC-BCS crossover
We present a new class of many-body quantum engine that we termed Pauli engine. Our engine which exploits genuine nonclassical forms of energy different from heat: it is fueled by the energy associated with the change of the statistical behavior of the working medium from bosonic to fermionic and back. We experimentally realized the Pauli cycle by driving a trapped ultracold two-component Fermi gas of $^6$Li atoms between a molecular Bose-Einstein condensate and a unitary Fermi gas. We obtain an efficiency of up to 25%. Our findings establish quantum statistics as a useful thermodynamic resource for work production.
Reference:
J. Koch, K. Menon, E. Cuestas, S. Barbosa, E. Lutz, T. Fogarty, Th. Busch, and A. Widera, arXiv:2209.14202 (2022)
6 – Giulia De Rosi
UPC – Universitat Politècnica de Catalunya
Thermal fading of the 1/k^4-tail of the momentum distribution induced by the hole anomaly
We provide the Path Integral Monte Carlo calculation of the momentum distribution in a 1D repulsive Bose gas. We explore all interaction and thermal regimes. The hole-anomaly temperature identifies a peak in the specific heat. We find that at large momentum k and temperature above the anomaly threshold, the tail C/k^4 of the distribution (proportional to the Tan contact C) is screened due to the thermal increase of the internal energy. We obtain the analytic tail for the distribution and a minimum momentum fixing its validity, both valid for any interaction and temperature, crossing from quantum to classical gas limit.
7 – Adolfo del Campo
University of Luxembourg
Tailoring Dynamical Fermionization: Delta kick cooling of a Tonks-Girardeau gas
Delta kick cooling (DKC) is used to compress the momentum distribution of ultracold quantum matter. It combines expansion dynamics with the use of kick pulses, designed via classical methods, that bring the system to rest. We introduce an exact approach to DKC for arbitrary scale-invariant dynamics of quantum gases, lifting the original restrictions to free evolution and noninteracting systems, to account for the control of atomic clouds in a time-dependent harmonic trap that can be either repulsive (inverted) or confining. We show that DKC assisted by a repulsive potential outperforms the conventional scheme, and that sudden trap-frequency quenches combined with DKC are equivalent to time-optimal bang-bang protocols. We further show that reverse engineering of the scale-invariant dynamics under smooth trap-frequency modulations can be combined with DKC to introduce a new class of shortcuts to adiabaticity assisted by kicks.
8 – Tilman Enss
Heidelberg University
Polaron interaction in superfluids
We investigate the induced Casimir interaction between two impurities
in superfluid atomic gases. With the help of effective field theory
(EFT) for a Galilean invariant superfluid, we find that the induced
impurity-impurity potential at long distance does not fall off
exponentially as a Yukawa potential, but instead exhibits a universal
power-law scaling. We show that the exchange of two phonons leads to a
relativistic van der Waals-like attraction (∼1/r^7) at zero
temperature and a nonrelativistic van der Waals attraction (∼T/r^6) at
finite temperature.
9 – Giovanni Ferioli
Institut d’Optique Graduate School
A non-equilibrium superradiant phase transition in free space
The interplay between driving and collective dissipation can stabilize nontrivial non-equilibrium phase. The simplest example is the Driven Dicke model which investigates the effect of a coherent pump in a superradiant ensemble. After having implemented this iconic model for the first time in free space [1], we now study the photon statistics of the light emitted by the cloud, observing a doubling of the oscillation frequency of g2(t) with respect to the single atom case. This behavior sheds a light on the time-crystalline nature of this driven-dissipative system.
[1] Ferioli et al., arXiv 2207, 1036 (2022) (Nat. Physics in press)
10 – Malthe Fiil Andersen
Aarhus University
Expansion of Mixed Thermal and BEC Clouds
Data from cold atom clouds are often acquired through absorption imaging after a short time-of-flight expansion. To get consistent and useful data from this method, accurate models of the expansion of clouds are needed. At finite temperatures, but below the critical BEC temperature, the atoms are in a mixed state of thermal and BEC atoms. Usually, these two components are assumed to not interact with each other, however, this assumption leads to small errors. I present a more accurate model and comparisons between calculated physical values using this model and the old one.
11 – Marcos G. dos Santos Filho
RHEINLAND-PFÄLZISCHE TECHNISCHE UNIVERSITÄT KAISERSLAUTERN-LANDAU
Incompressible energy spectrum from wave turbulence
Bose–Einstein condensates with their superfluidity property provide an interesting parallel to classical fluids. Due to the Kolmogorov spectrum of homogeneous turbulence the statistics of the incompressible velocity field is of great interest, but in superfluids obtaining quantities such as the statistics of the velocity field from the macroscopic wavefunction turns out be a complicated task; therefore, most of the work up to now has been numerical in nature. We made use of the Weak Wave Turbulence (WWT) theory, which provides the statistics of the macroscopic wavefunction, to obtain the statistics of the velocity field, which allowed us to produce a semi analytical procedure for extracting the incompressible energy spectrum in the WWT regime. This is done by introducing an auxiliary wavefunction that preserves the relevant statistical and hydrodynamical properties of the condensate but with a homogeneous density thus allowing for a simpler description of the velocity field.
12 – Diego Hernandez Rajkov
LENS
Universality of the superfluid Kelvin-Helmholtz instability by single-vortex tracking
We report on the observed universal behavior of the Kelvin-Helmholtz in strongly interacting Fermi gases across the BEC-BCS crossover. Extracting the instability growth rates by tracking the position of individual vortices we found that they follow universal scaling relations predicted by classical hydrodynamics.
13 – Mengzi Huang
ETH Zurich
Irreversible entropy transport between fermionic superfluids
The nature of the flow between two superfluids, as in the Josephson and fountain effects, is often understood in terms of reversible flow carried by an entropy-free, macroscopic wavefunction. However, its interplay with excitations in non-equilibrium situations is less understood. Here, we observe the nonlinear response of an irreversible entropy current to biases in chemical potential and temperature through a ballistic channel between two trapped and strongly interacting Fermi gases. Remarkably, the transported entropy per particle is robust to changes in the channel’s geometry and much larger than the local entropy of the equilibrium superfluid.
14 – Maciej Bartłomiej Kruk
Institute of Physics, Polish Academy of Sciences
Stationary, dynamic and thermal properties of quantum droplets
We present our findings with regards to quantum droplets that differ from the usual extended form in 3D by being flattened, elongated, or at nonzero temperature, but not yet in a hard low dimensional regime that would modify the LHY term. We compare the Bose-Bose droplet stability at zero and finite temperatures. For finite temperature cases we show existence of a critical temperature above which droplets exhibit finite lifespan and show statistics of droplet size and lifetime as a function of temperature.
15 – Yevhenii Kuriatnikov
Technische Universität Wien
OPTICAL POTENTIALS FOR QUANTUM FIELD SIMULATORS UTILIZING PHYSICS-INSPIRED LEARNING ALGORITHMS
One-dimensional, tunnel-coupled BECs can play the role of quantum simulators for studying quantum properties of multimode bosonic Josephson junctions and the Sine-Gordon model. Those simulations require a high level of control over the 1D trapping potential, which DMDs can provide. We present an iterative learning control algorithm and a physics-inspired machine learning-based model to optimize desired optical potentials. We drastically reduce the required number of experimental iterations by utilizing offline closed-loop feedback optimization. Furthermore, our methods hold great promise for the dynamic manipulation of ultracold gases and provide insights into how existing machine-learning methods can be used in quantum experiments.
16 – Benjamin Liegeois
ETH Zürich
Critical and Floquet dynamics of the Calogero model
We investigate dynamics of the Calogero model describing a trapped one-dimensional quantum gas with inverse square interaction under both periodic drive of the trap frequency and slow drive of the latter through the critical point. To this extent, we take advantage of the su(1,1) dynamical symmetry giving rise to scaling dynamics and uncover signatures of the interactions in the ground state fidelity of the system. Given the interpretation of the model in terms of exclusion statistics, this sheds light on the influence of statistics on the dynamics of periodically driven systems and systems in the vicinity of critical points.
17 – Wenliang Liu
Italian National Research Council (CNR-INO)
A new ytterbium experiment for single atom resolved physics
Ytterbium, as an alkaline-earth-like atom (AEA), features a rich electronic level stucture, offering many advantages over alkali atoms. The nuclear spin sub-states of the 1S0 ground and 3P0 clock states are ideal for encoding quantum information, owing to their weak sensitivity to external magnetic and electric fields, and to their SU(N) collisional symmetry, which increases the flexibility of quantum information and quantum simmulation schemes.
18 – Jamotte Maxime
Université Libre de Bruxelles
Strain and pseudo-magnetic fields in optical lattices from density-assisted tunneling
We explore how density-assisted tunneling can be tailored in view of simulating the effects of strain in synthetic graphene-type systems by considering a mixture of two atomic species on a honeycomb optical lattice: one species forms a Bose-Einstein condensate in an harmonic trap, whose inhomogeneous density profile induces an effective uniaxial strain for the second species through density-assisted tunneling processes, activated by time-periodic modulations. As in strained graphene, the second species experiences a pseudo-magnetic field, hence exhibiting relativistic Landau levels. Our scheme introduces a unique platform for investigating strain-induced gauge fields and their interplay with quantum fluctuations and collective excitations.
19 – Ivan Morera Navarro
University of Barcelona
Kinetic magnetism in the frustrated Fermi-Hubbard model
We study kinetic magnetism for the Fermi-Hubbard model in triangular lattices. We focus on the regime of strong interactions, U ≫ t and filling factors around one electron per site. For temperatures well above the hopping strength t, the Curie-Weiss form of the magnetic susceptibility suggests two complementary forms of kinetic magnetism. In the case of hole doping, antiferromagnetic polarons originate from kinetic frustration of individual holes, whereas for electron doping, Nagaoka type ferromagnetic correlations are induced by propagating doublons. These results provide a possible theoretical explanation of recent experimental results in moiré transition metaldichalcogenide materials and cold atom systems in triangular optical lattices. Direct observations of magnetic polarons in triangular lattices can be achieved in experiments with ultracold atoms, which allow measurements of three point hole-spin-spin correlations.
20 – Tyler Neely
University of Queensland
Decaying quantum 2D turbulence realised through the Kelvin-Helmholtz instability
After preparing an optimised persistent current state using machine learning, we experimentally study the dynamics of a superfluid shear layer in an 87Rb BEC. The interaction between the rotating and stationary superfluids results in a vortex necklace that rapidly decays, resulting in a ring of quantised vortices. This vortex ring is unstable and decays into vortex clusters, indicative of the superfluid Kelvin-Helmholtz instability. By studying the cluster sizes with increasing hold time, we find power-law behaviour analogous to decaying classical 2D turbulence.
21 – Meera Parish
Monash University
Fermi polarons: from cold atoms to two-dimensional semiconductors
The Fermi polaron, an impurity particle dressed by excitations of a fermionic medium, has been extensively studied in ultracold atomic gases. Recently, it was realised that the optical response of doped atomically thin semiconductors also corresponds to a quantum impurity problem, where excitons are introduced into an electronic medium. We will present different scenarios where we have recently used cold-atom-inspired Fermi polaron theories to explain the behavior in doped semiconductors. These examples in turn have the potential to shed new light on the cold atom polaron problem.
22 – Jordi Pera
Universitat Politècnica de Catalunya, BQMC
Beyond universality in repulsive SU(N) Fermi gases
Itinerant ferromagnetism in dilute Fermi gases is predicted to emerge at values of the gas parameter where second-order perturbation theory is not accurate enough to properly describe the system. We have revisited perturbation theory for SU(N) fermions and derived its generalization up to third order both in terms of the gas parameter and the polarization. Our results agree satisfactorily with quantum Monte Carlo results for hard-sphere and soft-sphere potentials for S = 1/2. Although the nature of the phase transition depends on the interaction potential, we find that for a hard-sphere potential a phase transition is guaranteed to occur. While for S = 1/2 we observe a quasi-continuous transition, for spins 3/2 and 5/2, a first-order phase transition is found. For larger spins, a double transition (combination of continuous and discontinuous) occurs. The critical density reduces drastically when the spin increases, making the phase transition more accessible to experiments with ultracold dilute Fermi gases. Estimations for Fermi gases of Yb and Sr with spin 5/2 and 9/2, respectively, are reported.
23 – Aurélien Perrin
CNRS
Toward unidimensional Bose gases with tunable interactions
The BEC team at Laboratoire de Physique des Lasers in Villetaneuse (France) has built an experimental setup able to produce quasi-unidimensional Bose gas of sodium on top of an atomchip. The latter encompasses a microwave waveguide that can be used to access microwave induced Feshbach resonances that have been predicted for all alkaline atoms but never observed so far. This poster will present preliminary results on the microwave spectroscopy of sodium molecular states and perspectives about the characterization of the Feshbach resonance.
24 – Verdiana Piselli
CNR – INO, University of Camerino
Time-dependent dynamics of a two-component Fermi gas
Atomic quantum gases offer a valid platform for building a quantitative understanding of out-of-equilibrium dynamics of superconducting systems. In this context, we have solved the time-dependent BdG equations to study the dynamics of a two-component Fermi gas following the action of time-dependent perturbations, aiming at providing a realistic account (as well as possible previsions) of occuring phenomena.
The perturbations we have considered are:
-separation of spin-up and spin-down fermions by an external spin-dependent potential;
-quench of the inter-particle interaction;
-up and down ramp of a spin-independent external potential.
Preliminary results along these lines will be presented.
25 – Lorenzo Pizzino
University of Geneva
Dimensional crossover in strongly correlated quasi-1D systems
Correlated electron states are at the root of many important phenomena including unconventional superconductivity (USC). We compute the properties of quasi-1D system made of weakly-coupled chains of correlated electrons, such as the critical temperature Tc for the onset of USC. By implementing a field-theory approach, we show how the analytical results can improve the efficiency and reliably of numerical methods such as combined matrix product states with static mean field.
26 – Abel Rojo Francàs
Universitat de Barcelona
Few distinguishable fermions in a one-dimensional harmonic trap
In this work we study static properties of few interacting distinguishable fermions trapped in a one-dimensional harmonic trap, focusing on the case of non-symmetric interactions between different fermions. We study both the low-energy spectrum and ground-state properties by means of an exact diagonalization of the Hamiltonian. We find that non-symmetric interactions lead to non-trivial states in the limit of strong repulsive interaction. We provide an exhaustive analysis and interpretation of these non-trivial solutions.
27 – Lorenzo Rossi
ICFO
Topology in the space-time scaling limit of quantum dynamics
We investigate the role of topology in the space-time scaling limit of quantum quench dynamics, where both time and system size tend to infinity at a constant ratio. While the standard topological characterization becomes ill defined, we show how a novel dynamical notion of topology naturally arises through a dynamical winding number encoding the linear response of the Berry phase to a magnetic flux. Specifically, we find that the presence of a locally invisible constant magnetic flux is revealed by a dynamical staircase behavior of the Berry phase, whose topologically quantized plateaus characterize the space-time scaling limit of a quenched Rice-Mele model.
28 – Rishabh Sharma
Université Sorbonne Paris Nord, Laboratoire de Physique des Lasers (LPL)
Non destructive imaging of a fast rotating quantum gas on the surface of a bubble-shaped trap
The aim of the work that I will present in the poster is to study the superfluid dynamics of a quantum gas trapped on the curved surface of a bubble-shaped trap. First I will present a new trapping configuration and loading procedure for the realization of the bubble trap, based on an hybrid quadrupole-dimple trap. This helps reducing the superfluid excitations during the loading of the bubble trap. Our starting point is a magnetic quadrupole trap, modified by a red detuned laser beam. After producing a quantum gas, we switch on a radiofrequency (rf) field to dress the atoms. We then slowly ramp up the rf frequency, thus inflating the resonant rf surface – a bubble – up to the point where it catches the atoms. This resonant surface is our final bubble trap. To study the superfluid dynamics on the surface of the bubble trap we put our quantum gas in rapid rotation by rotating a trap anisotropy. Then, I will present the non-destructive imaging method that we are currently implementing. The motivation behind this is to take multiple images, in a single experimental sequence, of the rotating gas. We expect to record a movie of almost 100 pictures of the rotating gas.
29 – Fernando Sols
Universidad Complutense de Madrid
Superfluidity from correlations in driven boson systems
We investigate theoretically the superfluidity of a one-dimensional boson system whose hopping energy is periodically modulated with a zero time average, which results in the suppression of first-order single-particle hopping processes. The dynamics of this Floquet-engineered flat-band system is entirely driven by correlations and described by exotic Hamiltonian and current operators. We employ exact diagonalization and compare our results with those of the conventional, undriven Bose-Hubbard system. We focus on the two main manifestations of superfluidity, the Hess-Fairbank effect and the metastability of supercurrents, with explicit inclusion of an impurity when relevant. Among the novel superfluid features, we highlight the presence of a cat-like ground state, with branches that have opposite crystal momentum but carry the same flux-dependent current, and the essential role of the interference between the collective components of the ground-state wave function. Calculation of the dynamic form factor reveals the presence of an acoustic mode that guarantees superfluidity in the thermodynamic limit.
30 – Gabriele Spada
Pitaevskii BEC Center, CNR-INO, Trento, Italy
Attractive solution of binary Bose mixtures: Liquid-vapor coexistence and critical point
I will present a novel study of the thermodynamic behavior of attractive binary Bose mixtures using exact path-integral Monte-Carlo methods. The focus is on the regime of interspecies interactions where the ground state is in a self-bound liquid phase, stabilized by beyond mean-field effects. Calculating the isothermal curves in the pressure vs density plane, we established the extent of the coexistence region between liquid and vapor and we determined the critical point where the line of first-order transition ends. Notably, within the coexistence region, Bose-Einstein condensation occurs in a discontinuous way that could be observed in experiments of mixtures in traps, as the density jumps from the normal gas to the superfluid liquid phase.
31 – Laurits Nikolaj Stokholm
Aarhus University
Spatial calibration of high density absorption imaging
The accurate determination of atom numbers is a ubiquitous problem in the field of ultracold atoms, in particular for optically dense clouds. The most commonly applied method in this regime takes advantage of the fact that the measured atomic density must be independent of the properties of the probe beam. By imaging samples at a fixed density with different probe intensities, the saturation intensity can be corrected to provide accurate atom numbers at moderate densities. We apply this technique to ultracold atoms and observe a dependence of the correction coefficient on optical density and the number of photons absorbed per atom. We present a simple recipe to incorporate this calibration method into the evaluation of absorption images and find a correction on the order of 10 % to the estimated atom numbers and temperatures under typical experimental conditions.
32 – Koushik Swaminathan
Aalto University
Superconductivity and Localization in Lattice Models with Flat Bands
We construct a class of exact eigenstates of the Hamiltonian obtained by projecting the Hubbard interaction term onto the flat band subspace of a generic lattice model. These exact eigenstates are many-body states in which an arbitrary number of localized fermionic particles coexist with a sea of mobile Cooper pairs with zero momentum. By considering the dice lattice as an example, we provide evidence that these exact eigenstates are in fact manifestation of local integrals of motions of the projected Hamiltonian. In particular the spin and particle densities retain memory of the initial state for a very long time, if localized unpaired particles are present at the beginning of the time evolution. This shows that many-body localization of quasiparticles and superfluidity can coexist even in generic two-dimensional lattice models with flat bands, for which it is not known how to construct local conserved quantities. Our results open new perspectives on the old condensed matter problem of the interplay between superconductivity and localization.
33 – Amit Upadhyay
Indian Institute of Technology Bombay
Coherent population dynamics of the correlated spin system in the Markovian limit
The large molecules in the presence of complex environment are modeled as spin-boson or correlated spin systems in order to understand the excitonic energy transfer (EET). We have obtained the optical Bloch equations for the two coupled two-level systems (TLS) using the Lindbladian Master equation and derived the analytical expressions of the excited state populations of the correlated spins, both in the exciton and site basis, in the presence of independent heat baths. Also, the analytical solution of steady-state populations in the site basis are attained. The population dynamics in the Markovian regime is numerically simulated for the bacteriochlorophyll molecules found in the Fenna-Mathhews-Olsen (FMO) complex of green sulfur bacteria.
34 – Toke Vibel
Department of Physics and Astronomy, Aarhus University
Unraveling Experimental Noise: Understanding Atom Number Fluctuations in a Bose-Einstein Condensate
Bose-Einstein condensation (BEC) of weakly interacting atomic gases is crucial in modern atomic physics research, requiring a deep understanding for practical applications. While the mean atom number in partly condensed clouds is well-understood, the fluctuations have remained a puzzle until recently. Here I present our breakthrough in characterizing these atom number fluctuations. Our observations reveal a reduction in the fluctuations below the canonical expectation for noninteracting gases, shedding light on the microcanonical nature of our system. Additionally, I will discuss our recently enhanced data analysis, which considers various noise contributions in the experimental procedure.
35 – Kali Wilson
University of Strathclyde
Using vortices as probes of quantum many-body systems
Quantised vortices, topologically-protected defects, are ideal probes of the cooperative behaviour inherent in superfluid systems, as their nucleation, internal structure, and dynamics depend directly on the microscopic physics at play. Furthermore, vortices play an integral role in the dissipation of energy in these systems. I will discuss how vortices may be used to probe binary superfluids and quantum-fluctuation-enhanced regimes, and how this might be implemented experimentally. I will also present an overview of the experimental capabilities under development at the University of Strathclyde to enable studies of vortex dynamics in binary superfluids.
36 – Gabriel Wlazłowski
Warsaw University of Technology
Towards general-purpose simulation platform for superfluid fermions
Numerical simulations are an important ingredient of modern research. In the field of Bose-Einstein condensates, the Gross–Pitaevskii equation (GPE) is a workhorse that facilitates the interpretation of experimental data for various setups. The counterpart of GPE for superfluid fermions are mean-field Bogoliubov-de Gennes (BdG) equations. Formally, their applicability is limited to weak couplings, while the experiments typically operate for strong couplings (around the unitary limit). The density functional theory (DFT) can be a remedy for this disparity. It is a versatile method describing with very good accuracy the static, dynamic, and thermodynamic properties of many-body Fermi systems in a unified framework, while keeping the numerical cost at the same level as the mean-field approach. I will summarize developments of the DFT dedicated to ultracold atomic gases across BCS-BEC crossover, together with its open-source numerical implementation (W-SLDA Toolkit). Selected applications of the method to various experimental setups will be presented.
37 – Klejdja Xhani
CNR – INO
Stability of persistent currents in annular atomic superfluids in the presence of multidefects
Superfluids in multiple-connected geometries are characterized by the presence of persistent currents. Here, we theoretically investigate the role of vortices on its decay in atomic superfluids by solving numerically the Gross-Pitaevskii equation, and directly compare our results with experimental data. We firstly show that in the case of a single defect it exists a critical circulation wc such that for initial values larger than wc the supercurrent decays through the emission of vortices. Next, we extend our studies to the case of many defects. Surprisingly, we find that increasing the number of defects could stabilize the supercurrent.
38 – Tianwei Zhou
Department of Physics and Astronomy, University of Florence
Strongly interacting lattice fermions with coherent state manipulation: from universal Hall response to Hall voltage measurement
We report on the direct measurements of current and charge polarization in an ultracold-atom simulator, where we trace the buildup of the Hall response in a synthetic ladder pierced by a magnetic flux, going beyond stationary Hall voltage measurements in solid-state systems. We witness the onset of a clear interaction-dependent behavior, where the Hall response deviates significantly from that expected for a non-interacting electron gas, approaching a universal value. As a further step to access the experimental value of the Hall voltage, we have recently implemented a synthetic gradient so as to counteract the Hall drift.
39 – Robert Zillich
Johannes Kepler University
Non-Equilibium Dynamics in a Quantum Gas: Time-Dependent Hypernetted-Chain Euler-Lagrange Studies
We present a variational method to study the dynamics of a closed bosonic many-body system, the time-dependent hypernetted-chain Euler-Lagrange (tHNC) method. Based on the Jastrow ansatz, it accounts for correlations in a non-perturbative way. We apply the tHNC method to interaction quenches, i.e. sudden changes of the interaction strength, in Bose gases and to harmonic perturbations of a dipolar Bose gas. We find good agreement between tHNC results and time-dependent variational Monte Carlo results.
40 – Cesar Cabrera
University of Hamburg
Long-lived Higgs mode in a strongly interacting superfluid
Arising from broken continuous symmetry, in the Ginzburg-Landau theory, an amplitude mode is a fundamental excitation of the order parameter Δ, which characterizes the long-range order of superfluids. In my poster, I will show that an ultracold quasi-2D Fermi gas exhibits a long-lived amplitude mode in the strongly interacting regime. We excite the amplitude mode via trapping modulation spectroscopy and observe a narrow resonance located at 2Δ , which we attribute to the excitation energy and lifetime of the mode. We support these results by directly measuring the coherent oscillations of the momentum distribution.