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We wish you relaxing holidays and a fantastic New Year! We created this Christmas card with our new homogeneous unitary Fermi gas in tailored optical potentials. The gas is trapped in a 3D box potential created by two DMDs shining repulsive light both in the vertical and in the horizontal directions. Each frame consist in a single-shot image of the unitary gas with sculpted optical potential with the vertical DMD, imaged with our high-resolution microscope objective. We divide each frame into 16 or 20 segments to exploit the full resolution of the optical setup to accurately reproduce the videos on our atomic display. Feliz Navidad! Buon Natale! |
LAST NEWS
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When a superconductive Josephson junction is driven by an oscillating current, it develops a series of evenly spaced voltage plateaus known as Shapiro steps, like climbing a quantum staircase. As the height of each step is directly determined by the frequency of the applied current, the Shapiro steps provide the definition of the voltage standard. In this work, we report the observation of Shapiro steps in periodically driven Josephson junctions of strongly interacting Fermi superfluids of ultracold atoms. Similarly to the superconducting case, we observe quantized plateaus in the current–potential characteristics, which plays the role of the voltage in neutral atomic Josephon junctions. By measuring the junction relative phase, we also directly probe the current–phase relationship, showing that Shapiro steps originate from the synchronization of the junction relative phase with the applied drive. In the n-th Shapiro steps the junction phase undergoes to n phase slips event, which we directly visualize as the emission of n vortex-antivortex pairs. G. Del Pace et al.
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Mutual friction is a fundamental mechanism in finite-temperature superfluids, arising from vortex scattering with thermally excited quasiparticles and directly influencing vortex dynamics. Its microscopic origin is determined by the intrinsic properties of the system and the nature of its excitations. We investigate the two-dimensional motion of a single vortex orbiting a pinned anti-vortex in a unitary Fermi atomic superfluid at varying temperatures. From the observed trajectory, we extract the previously unknown longitudinal and transverse mutual-friction coefficients, which quantify the vortex-mediated coupling between the normal and superfluid components. Our results suggest that vortex dynamics in unitary Fermi superfluids is essentially affected by the interplay between delocalized thermal excitations and vortex-bound quasiparticles localized within the vortex core, the so-called Caroli–de Gennes–Matricon states. Further, from the mutual friction coefficients we determine the vortex Hall angle, which is linked to the relaxation time of the localized quasiparticles occupying Andreev bound states within the vortex core, and to the vortex Reynolds number associated with the transition from laminar to quantum turbulent flows. N. Grani, D. Hernández-Rajkov et al. For details on the data analysis see also: N. Grani, et al. |
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The Hall effect is a cornerstone of modern science, spanning applications from cutting-edge technologies to the discovery of exotic topological phases of matter. In solid-state systems, it manifests as a voltage perpendicular to current flow in a magnetic field, giving rise to transverse Hall resistance. Yet, its behavior in quantum systems remains elusive. Using neutral-atom quantum simulators, we introduce the first direct measurement of Hall voltage and resistance in a non-electron-based system. This work links quantum simulations to real-world experiments, unlocking new avenues to explore the Hall effect in tunable, strongly correlated systems. T.-W. Zhou et al. |
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A new PhD course is starting, and with it comes a wave of new students joining our team. An injection of fresh energy, curiosity, and ideas! Welcome to Michael Stiven Caracas Núñez (BaLi), Èlia Solé Cardona (Dy), Alessandro Vanni (Yb Tweezers), and Alberto Terenzi (Li). |