Many-body quantum phases of dipolar gases

by Claudia Politi

Abstract:

Since the realization of the first Bose-Einstein condensate in 1995, the number of quantum-gas experiments grew enormously, involving different atomic species ranging from alkali metals, such as rubidium, to triel elements, with the new-come indium. This huge interest is motivated by the high control that quantum gases offer in terms of interatomic interactions, dimensionality of the system, and the possibility of adding complexity in a controlled manner. For this reason, in the past decades, ultracold atoms revealed to be ideal platforms for simulating many-body phenomena, linked to various fields as condensed-matter physics, high-energy physics, and quantum optics. Ultracold gases interact usually with a short-range and isotropic contact-type interaction. The achievement of degenerate gases with highly-magnetic atoms, such as chromium, erbium, dysprosium, and just recently thulium and europium, which possess a permanent magnetic moment in the ground state, led to richer interactions, showing a long-range and anisotropic nature. The addition of this new ingredient to the quantum-gas tool box brought to the discovery of interesting many-body phases, as quantum droplets, and supersolid states, showing both superfluid and crystalline order. The work presented in this thesis focuses on two main topics. The first part reports on the investigation of the interspecies interactions between the two highly magnetic lanthanides, erbium and dysprosium, with a focus on the role played by the dipole-dipole interaction. It presents an alternative method to estimate the interspecies scattering length from the in-trap clouds displacement, and it shows how tuning the interspecies repulsion can lead to binary supersolid states. The second part focuses on the creation of a dipolar supersolid state with dysprosium atoms. It first gives insights on the role played by finite temperatures in the superfluidto- supersolid phase transition. It then presents the first realization of two-dimensional supersolid states, first in a zig-zag pattern, and then in a hexagon pattern. The realization of two-dimensional supersolidity opens the door to many research directions, such as the investigation of the excitation modes, quantized vortices, and persistent currents.

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Reference:

Many-body quantum phases of dipolar gases,
Claudia Politi,
PhD Thesis, 2022.

Bibtex Entry:

@article{PolitiPhD,
  title = {Many-body quantum phases of dipolar gases},
  author = {Politi, Claudia},
  journal = {PhD Thesis},
  year = {2022},
  month = {Dec},
  abstract = {Since the realization of the first Bose-Einstein condensate in 1995, the number of
quantum-gas experiments grew enormously, involving different atomic species ranging
from alkali metals, such as rubidium, to triel elements, with the new-come indium.
This huge interest is motivated by the high control that quantum gases offer in terms
of interatomic interactions, dimensionality of the system, and the possibility of adding
complexity in a controlled manner. For this reason, in the past decades, ultracold
atoms revealed to be ideal platforms for simulating many-body phenomena, linked to
various fields as condensed-matter physics, high-energy physics, and quantum optics.
Ultracold gases interact usually with a short-range and isotropic contact-type
interaction. The achievement of degenerate gases with highly-magnetic atoms, such
as chromium, erbium, dysprosium, and just recently thulium and europium, which
possess a permanent magnetic moment in the ground state, led to richer interactions,
showing a long-range and anisotropic nature. The addition of this new ingredient to
the quantum-gas tool box brought to the discovery of interesting many-body phases,
as quantum droplets, and supersolid states, showing both superfluid and crystalline
order.
The work presented in this thesis focuses on two main topics. The first part
reports on the investigation of the interspecies interactions between the two highly
magnetic lanthanides, erbium and dysprosium, with a focus on the role played by the
dipole-dipole interaction. It presents an alternative method to estimate the interspecies
scattering length from the in-trap clouds displacement, and it shows how tuning the
interspecies repulsion can lead to binary supersolid states.
The second part focuses on the creation of a dipolar supersolid state with dysprosium
atoms. It first gives insights on the role played by finite temperatures in the superfluidto-
supersolid phase transition. It then presents the first realization of two-dimensional
supersolid states, first in a zig-zag pattern, and then in a hexagon pattern. The
realization of two-dimensional supersolidity opens the door to many research directions, such as the investigation of the excitation modes, quantized vortices, and persistent
currents.},
  url = {http://www.erbium.at/FF/wp-content/uploads/2023/07/PhDThesis_Politi_Dec22_final.pdf},
}