Periodic Reporting for period 4 - RARE (Dipolar Physics and Rydberg Atoms with Rare-Earth Elements)
Periodo di rendicontazione: 2021-01-01 al 2022-06-30
The overall objective of the RARE project is the investigation of dipolar quantum gases and quantum mixtures of the strongly magnetic rare-earth atomic species erbium and dysprosium. Those species feature a strong anisotropic and long-range dipole-dipole-interaction (DDI), which makes them ideal candidates to study few- and many-body dipolar quantum physics, opening the way to explore exotic quantum phases of matter otherwise not accessible. They will also allow to realize unique quantum simulators, where a well controllable quantum system is used to simulate very complicated or not easily accessible systems like condensed-matter materials, allowing an in-depth investigation of e.g. quantum magnetism.
The project follows three main lines of research: (A) to realize strongly magnetic dipolar quantum mixtures with the aim to experimentally produce and study exotic states of matter; (B) to investigate dipolar phenomena in very low or even zero polarizing magnetic fields, where new quantum phases related to the spin-orbit coupled nature of dipolar gases or quantum nematic phases are expected to exist; (C) to open new horizons in the field of Rydberg physics by exploiting the multi-electron nature of erbium which will add novel degrees of freedom to those systems like simultaneous trapping, manipulating, detecting and cooling of Rydberg excited atoms.
We successfully build up a new fully functional experiment combining erbium and dysprosium, produced double-degenerate Bose-Bose and Bose-Fermi mixtures and studied their scattering and interaction properties. Using fermionic erbium alone we were able to produce a strongly-interacting Fermi-Fermi mixture of two spin states. By combining the control over the spin state with an optical lattice we realized the so-called Heisenberg XXZ spin-model and performed quantum simulations of the spin dynamics in this model. Using bosonic erbium alone we observed the roton excitations in our dipolar gas, predicted to exist more than 20 years ago. This breakthrough pathed the way to the subsequent realization of the so-called supersolid, an exotic new state of matter with crystal-like structure and superfluid behaviour. In subsequent work we investigated its excitation properties with different complementary methods and were also able to produce this fascinating state in a two-dimensional geometry.
The project follows three main lines of research: (A) to realize strongly magnetic dipolar quantum mixtures with the aim to experimentally produce and study exotic states of matter; (B) to investigate dipolar phenomena in very low or even zero polarizing magnetic fields, where new quantum phases related to the spin-orbit coupled nature of dipolar gases or quantum nematic phases are expected to exist; (C) to open new horizons in the field of Rydberg physics by exploiting the multi-electron nature of erbium which will add novel degrees of freedom to those systems like simultaneous trapping, manipulating, detecting and cooling of Rydberg excited atoms.
We successfully build up a new fully functional experiment combining erbium and dysprosium, produced double-degenerate Bose-Bose and Bose-Fermi mixtures and studied their scattering and interaction properties. Using fermionic erbium alone we were able to produce a strongly-interacting Fermi-Fermi mixture of two spin states. By combining the control over the spin state with an optical lattice we realized the so-called Heisenberg XXZ spin-model and performed quantum simulations of the spin dynamics in this model. Using bosonic erbium alone we observed the roton excitations in our dipolar gas, predicted to exist more than 20 years ago. This breakthrough pathed the way to the subsequent realization of the so-called supersolid, an exotic new state of matter with crystal-like structure and superfluid behaviour. In subsequent work we investigated its excitation properties with different complementary methods and were also able to produce this fascinating state in a two-dimensional geometry.
The five-year duration of the RARE project has been divided in three main parts: (1) The construction phase of a new experimental apparatus (M1-18); (2) the intermediate result phase (M18-36); and (3) the main result phase (M36-60).
In the first phase of the project, a fully functional experimental setup being able to produce dipolar quantum mixtures of erbium and dysprosium was build up. The experimental setup consists of a complete vacuum apparatus and dedicated laser and magnetic field setups. The demonstration of simultaneous laser cooling of erbium and dysprosium, and dual magneto-optical trapping have been reported in a manuscript published in Phys. Rev. A 2018.
In the second phase of the project, we have produced the first double-degenerate dipolar quantum gas mixture using evaporative cooling in an optical dipole trap. We were able to prepare several isotope combinations to realize Bose-Bose and Bose-Fermi mixtures. These results have been published in Phys. Rev. Lett. (featured as Synopsis in Physics and selected as Editors’ Suggestion).
Simultaneously, we were able to create the first strongly-interacting Fermi-Fermi mixture of two spin states in erbium (published in Phys. Rev. Lett.). The large number of fermionic isotopes can be used for quantum simulation and lattice spin models, where we performed first experiments using erbium in a three-dimensional lattice and realized the so-called Heisenberg XXZ-model (published in Phys. Rev. Research).
Finally, we were able to observe rotonic excitations in our dipolar gas, which were predicted in theory about 20 years ago. This work has been published in Nature Physics and has attracted a high interest across many communities and led to the speculation that such systems could realize a new state of matter, the so-called supersolid. We were able to prepare this fascinating state in both species, with dysprosium exhibiting a very long lifetime, allowing us to directly cool into this state. This work has been published in Physical Review X (The paper has been featured as Viewpoint in Physics).
In the third phase of the project, we further investigated dipolar quantum gas mixtures of Er and Dy and have been able to observe broad interspecies Feshbach resonances in a variety of isotope combinations. We also experimentally probed interactions using the in-situ repulsion between the two species (both published in Phys. Rev. A).
In parallel we have performed high-resolution EIT Rydberg spectroscopy using an atomic beam of Er on a newly build separate experimental setup. With this, we could observe a multitude of Rydberg lines which, together with a multi-channel theoretical analysis in collaboration with theorists (published in Phys. Rev. Research).
We also further continued our survey on the supersolid state of matter. In particular, we experimentally probed the high-energy Bragg-scattering response and worked on a theory model for the experimental conditions (published in Phys. Rev. A and Phys. Rev. Research). For the long-lived dipolar supersolid in Dy, we were able to probe phase coherence in an out of equilibrium situation which has been published in Nature Physics and investigated the birth, life and death of the supersolid, showing that within the evaporation process the crystalline structure seems to appear before global phase coherence (published in Phys. Rev. Research).
In a major breakthrough we were able to observe supersolidity in two-dimensional systems, showing spontaneous symmetry breaking along two spatial dimensions, which has been published in Nature 2021 (associated News&Views article in Nature). Following this important step, we further investigated experimentally and theoretically the 2D systems in a series of works (published in Phys. Rev. A and Phys. Rev. Lett.).
Finally, we investigated rotating dipolar gases to directly create and detect quantized vortices. We successfully implemented a genuine scheme to introduce angular momentum by a rotating magnetic field and were able to produce and detect vortices and their special properties in a dipolar gas. Our results got recently published in Nature Physics 2022 (associated News&Views article in Nature Physics).
In the first phase of the project, a fully functional experimental setup being able to produce dipolar quantum mixtures of erbium and dysprosium was build up. The experimental setup consists of a complete vacuum apparatus and dedicated laser and magnetic field setups. The demonstration of simultaneous laser cooling of erbium and dysprosium, and dual magneto-optical trapping have been reported in a manuscript published in Phys. Rev. A 2018.
In the second phase of the project, we have produced the first double-degenerate dipolar quantum gas mixture using evaporative cooling in an optical dipole trap. We were able to prepare several isotope combinations to realize Bose-Bose and Bose-Fermi mixtures. These results have been published in Phys. Rev. Lett. (featured as Synopsis in Physics and selected as Editors’ Suggestion).
Simultaneously, we were able to create the first strongly-interacting Fermi-Fermi mixture of two spin states in erbium (published in Phys. Rev. Lett.). The large number of fermionic isotopes can be used for quantum simulation and lattice spin models, where we performed first experiments using erbium in a three-dimensional lattice and realized the so-called Heisenberg XXZ-model (published in Phys. Rev. Research).
Finally, we were able to observe rotonic excitations in our dipolar gas, which were predicted in theory about 20 years ago. This work has been published in Nature Physics and has attracted a high interest across many communities and led to the speculation that such systems could realize a new state of matter, the so-called supersolid. We were able to prepare this fascinating state in both species, with dysprosium exhibiting a very long lifetime, allowing us to directly cool into this state. This work has been published in Physical Review X (The paper has been featured as Viewpoint in Physics).
In the third phase of the project, we further investigated dipolar quantum gas mixtures of Er and Dy and have been able to observe broad interspecies Feshbach resonances in a variety of isotope combinations. We also experimentally probed interactions using the in-situ repulsion between the two species (both published in Phys. Rev. A).
In parallel we have performed high-resolution EIT Rydberg spectroscopy using an atomic beam of Er on a newly build separate experimental setup. With this, we could observe a multitude of Rydberg lines which, together with a multi-channel theoretical analysis in collaboration with theorists (published in Phys. Rev. Research).
We also further continued our survey on the supersolid state of matter. In particular, we experimentally probed the high-energy Bragg-scattering response and worked on a theory model for the experimental conditions (published in Phys. Rev. A and Phys. Rev. Research). For the long-lived dipolar supersolid in Dy, we were able to probe phase coherence in an out of equilibrium situation which has been published in Nature Physics and investigated the birth, life and death of the supersolid, showing that within the evaporation process the crystalline structure seems to appear before global phase coherence (published in Phys. Rev. Research).
In a major breakthrough we were able to observe supersolidity in two-dimensional systems, showing spontaneous symmetry breaking along two spatial dimensions, which has been published in Nature 2021 (associated News&Views article in Nature). Following this important step, we further investigated experimentally and theoretically the 2D systems in a series of works (published in Phys. Rev. A and Phys. Rev. Lett.).
Finally, we investigated rotating dipolar gases to directly create and detect quantized vortices. We successfully implemented a genuine scheme to introduce angular momentum by a rotating magnetic field and were able to produce and detect vortices and their special properties in a dipolar gas. Our results got recently published in Nature Physics 2022 (associated News&Views article in Nature Physics).
We have been able to produce for the first time a dipolar quantum mixture. This is a completely novel system and very little is known about its quantum behaviour, ground-state properties, and out-of equilibrium dynamics.
We have been able to observe for the first time rotonized excitations in a dipolar quantum gas. They have pathed the way for the production of a new state of matter, the long-sought supersolids.
We have been able to prepare for the first time supersolid states in one and two dimensions in a dipolar quantum gas. Predicted over 50 years ago, this counterintuitive state finally can be investigated in great detail.
We have been able to produce for the first time quantized vortices in a dipolar quantum gas. Those vortices are expected to feature new properties, and the genuine new method to produce them might allow future studies of vortices in supersolids.
We have been able to observe for the first time rotonized excitations in a dipolar quantum gas. They have pathed the way for the production of a new state of matter, the long-sought supersolids.
We have been able to prepare for the first time supersolid states in one and two dimensions in a dipolar quantum gas. Predicted over 50 years ago, this counterintuitive state finally can be investigated in great detail.
We have been able to produce for the first time quantized vortices in a dipolar quantum gas. Those vortices are expected to feature new properties, and the genuine new method to produce them might allow future studies of vortices in supersolids.