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Sound, superfluidity and layer compressibility in a ring dipolar supersolid
We propose a protocol to excite the Goldstone modes of a supersolid dipolar Bose-Einstein condensed gas
confined in a ring geometry. By abruptly removing a properly applied periodic modulation,
we explore the resulting oscillations of the gas, by solving the extended Gross-Pitaevskii equation. The value
of the two longitudinal sound velocities exhibited in the supersolid phase are analyzed using the hydrodynamic
theory of supersolids at zero temperature. This approach allows for the determination of the layer
compressibility modulus as well as of the superfluid fraction,
in agreement with the Leggett estimate of the non-classical moment of inertia.
Marija Šindik, Tomasz Zawiślak, Alessio Recati, Sandro Stringari, Phys. Rev. Lett. 132, 146001 (2024)
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Observation of false vacuum decay via bubble formation in ferromagnetic superfluids
In quantum field theory, the decay of an extended metastable state into the real ground state is known as ``false vacuum decay'' and it takes place via the nucleation of spatially localized bubbles. Despite the large theoretical effort to estimate the nucleation rate, experimental observations were still missing. Here, we observe bubble nucleation in isolated and highly controllable superfluid atomic systems, and we find good agreement between our results,
numerical simulations and instanton theory opening the way to the emulation of out-of-equilibrium quantum field phenomena in atomic systems.
Alessandro Zenesini, Anna Berti, Riccardo Cominotti, Chiara Rogora, Ian G. Moss,
Thomas P. Billam, Iacopo Carusotto, Giacomo Lamporesi, Alessio Recati, Gabriele Ferrari, Nature Physics (2024)
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Oscillating Solitons and AC Josephson Effect in Ferromagnetic Bose-Bose Mixtures
Close to the demixing transition, the degree of freedom associated to relative density fluctuations of a two-component Bose-Einstein condensate is described by a non-dissipative Landau-Lifshitz equation. In the quasi one-dimensional weakly immiscible case,
this mapping surprisingly predicts that a dark-bright soliton should oscillate when subject to a constant force favoring separation of the two components.
We propose a realistic experimental implementation of this phenomenon which we interpret as a spin-Josephson effect in the presence of a movable barrier.
Sebastiano Bresolin, Arko Roy, Gabriele Ferrari, Alessio Recati, Nicolas Pavloff, Phys. Rev. Lett. 130, 220403 (2023)
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Lattice polarons across the superfluid to Mott insulator transition
We study the physics of a mobile impurity confined in a lattice, moving within a Bose-Hubbard bath at zero temperature. Within the Quantum Gutzwiller formalism, we develop a beyond-Fröhlich model of the bath-impurity interaction. Results for the properties of the polaronic quasiparticle formed from the dressing of the impurity by quantum fluctuations of the bath are presented throughout the entire phase diagram, focusing on the quantum phase transition between the superfluid and Mott insulating phases. Here we find that the modification of the impurity properties is highly sensitive to the different universality classes of the transition, providing
an unambiguous probe of correlations and collective modes in a quantum critical many-body environment.
V. E. Colussi, F. Caleffi, C. Menotti, A. Recati, Phys. Rev. Lett. 130, 173002 (2023)
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Phase Diagram Detection via Gaussian Fitting of Number Probability Distribution
We investigate the number probability density function that characterizes sub-portions of a quantum many-body system with globally conserved number of particles. We put forward a linear fitting protocol capable of mapping out the ground-state phase diagram of the rich one-dimensional extended Bose-Hubbard model: The results are quantitatively comparable with more sophisticated traditional and
machine learning techniques. We argue that the studied quantity should be considered among the most informative bipartite properties, being moreover readily accessible in atomic gases experiments.
Daniele Contessi, Alessio Recati, Matteo Rizzi,
Phys. Rev. B, L121403 (2023)
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