by Gabriele Natale
Abstract:
Ultracold gases provide a versatile platform for trapping, controlling, and manipulating both external and internal degrees of freedom of the atoms. In particular, the experimental realization of Bose-Einstein condensates and degenerate Fermi gases inaugurated an exciting era of quantum-gas experiments to perform quantum simulations or investigate interesting quantum phases. Famous examples in our community are the superfluid to Mott-insulator phase transition and the bright soliton. In particular, the study of exotic quantum phases is the main topic of this thesis. A remarkably bizarre phase is the supersolid phase, which can arise from the competition between short and long-range interactions. In this state, two symmetries, the translational and the gauge symmetry, are spontaneously broken. For this reason, two antithetical orders coexist, and the system is simultaneously superfluid and crystal. In this thesis, we use dipolar gases of erbium atoms to find the regime in which a supersolid exists. We then ask the following question: how does this system manifest its properties? We answer this question by performing two different protocols to perturb this state and study its response. A particularly relevant result is the presence in the excitation spectrum of two branches. The first branch is related to crystal excitations, while the second to superfluid excitations. Furthermore, we approach the study of the quantum phases of an erbium condensate confined in reduced dimensions. By using a one-dimensional optical lattice, we load the atoms in an array of quasi-2D planes and study their distribution in the different lattice sites. We found that if the onsite dipole-dipole interaction is attractive on average, reducing the scattering length drives a localization of the atoms in a single lattice site. We assess the role that quantum fluctuations play in this geometry and discover a regime in which kinetic energy and quantum fluctuations compete to stabilize the system. This geometry gives rise to soliton or droplet solutions.
Reference:
Competing Interactions in Dipolar Quantum Gases of Bosonic Erbium Atoms,
Gabriele Natale,
PhD Thesis, 2022.
Gabriele Natale,
PhD Thesis, 2022.
Bibtex Entry:
@article{NatalePhD,
title = {Competing Interactions in Dipolar Quantum Gases of Bosonic Erbium Atoms},
author = {Natale, Gabriele},
journal = {PhD Thesis},
year = {2022},
month = {Dec},
abstract = {Ultracold gases provide a versatile platform for trapping, controlling, and manipulating both
external and internal degrees of freedom of the atoms. In particular, the experimental
realization of Bose-Einstein condensates and degenerate Fermi gases inaugurated an exciting
era of quantum-gas experiments to perform quantum simulations or investigate interesting
quantum phases. Famous examples in our community are the superfluid to Mott-insulator
phase transition and the bright soliton. In particular, the study of exotic quantum phases is
the main topic of this thesis.
A remarkably bizarre phase is the supersolid phase, which can arise from the competition
between short and long-range interactions. In this state, two symmetries, the translational
and the gauge symmetry, are spontaneously broken. For this reason, two antithetical orders
coexist, and the system is simultaneously superfluid and crystal.
In this thesis, we use dipolar gases of erbium atoms to find the regime in which a supersolid
exists. We then ask the following question: how does this system manifest its properties? We
answer this question by performing two different protocols to perturb this state and study
its response. A particularly relevant result is the presence in the excitation spectrum of two
branches. The first branch is related to crystal excitations, while the second to superfluid
excitations.
Furthermore, we approach the study of the quantum phases of an erbium condensate confined
in reduced dimensions. By using a one-dimensional optical lattice, we load the atoms in an
array of quasi-2D planes and study their distribution in the different lattice sites. We found
that if the onsite dipole-dipole interaction is attractive on average, reducing the scattering
length drives a localization of the atoms in a single lattice site. We assess the role that
quantum fluctuations play in this geometry and discover a regime in which kinetic energy
and quantum fluctuations compete to stabilize the system. This geometry gives rise to soliton
or droplet solutions.},
url = {http://www.erbium.at/FF/wp-content/uploads/2023/07/PhD thesis-GabrieleNatale.pdf},
}