Recent development of cooling and manipulating Ytterbium atoms opens a new avenue to investigate unprecedented atomic systems with SU(N) spin symmetry and orbital degrees of freedom. The available metastable states and narrow-line optical transitions of Ytterbium atoms allow for the versatile control of the system. Here, we first describe our apparatus for producing ultracold Ytterbium-173 quantum gases in an optical lattice. A gas of 3 × 104 Ytterbium173 atoms is routinely produced at T /TF ∼ 0.3, and loaded into an optical lattice potential. Then we report our recent progress on the spin orbital (SO) coupling interaction realized in optical lattice. As a novel quantum simulator, cold Ytterbium atoms with SO coupling provide a platform to explore the intriguing topological physics.
Recent development of cooling and manipulating Ytterbium atoms opens a new avenue to investigate unprecedented atomic systems with SU(N) spin symmetry and orbital degrees of freedom. The available metastable states and narrow-line optical transitions of Ytterbium atoms allow for the versatile control of the system. Here, we first describe our apparatus for producing ultracold Ytterbium-173 quantum gases in an optical lattice. A gas of 3 × 104 Ytterbium173 atoms is routinely produced at T /TF ∼ 0.3, and loaded into an optical lattice potential. Then we report our recent progress on the spin orbital (SO) coupling interaction realized in optical lattice. As a novel quantum simulator, cold Ytterbium atoms with SO coupling provide a platform to explore the intriguing topological physics.
We study ultracold quantum gases of alkaline-earth-like atoms loaded into three-dimensional statedependent optical lattice.In particular, we focus on the fermionic ytterbium-173 atoms due to their unique properties, in particular, low-lying metastable excited e electronic state, decoupling of the nuclear spin from the electronic degrees of freedom and different AC-polarizabilities of the ground g and e states.This allows to realize the two-band Hubbard model and study its unique critical properties.The theoretical analysis is performed in the region of applicability of the tight-binding approximation at different lattice depths and different fillings by atoms in the g-and e-orbital states.By means of dynamical mean-field theory, we analyze stability regions of the emerging ordered phases.
Recently, a new generation of experiments with ultracold quantum gases has emerged where the many-body properties are probed and manipulated using ultra-narrow “clock” transitions. We describe here our experimental project, which aims at engineering a special kind of optical lattice realizing an effective magnetic field coupling to the atomic motion - the Hofstadter optical lattice. Our specific experimental scheme uses the ultra-narrow optical transition linking the ground state to a metastable excited state of 174 Ytterbium atoms. We present the current status of the experiment, including the observation of coherent Rabi oscillations between the ground and excited states.
The optical lattice system with ultracold atoms is a promising platform for investigating many-body physics. We describe our ongoing efforts along this line for constructing a versatile ytterbium apparatus designed for the optical detection of atoms with high resolution. The apparatus already allows us to produce a quasi-pure Yb Bose-Einstein condensate of 40,000 atoms within 12s. Moreover sufficient atomic flux from the 65-cm long Zeeman slower would allow us to produce ytterbium Bose-Fermi mixture in which unprecedented many-body physics can be explored. In this poster, we report on our recent progress and describe our experimental setup.
Ultracold atoms provide a controllable platform to explore topological matter induced by spin-orbit (SO) coupling. This thesis reports an experimental realization of topological matter with Ytterbium atoms implemented by a Raman (or SO coupling) lattice - an optical lattice dressed by SO coupling, where internal atomic states are coupled by Raman beams. Remarkably, the lattice simultaneously serves as one of the Raman beams. As the building block of the Raman lattice, SO coupling is first studied in a one-dimensional (1D) bulk system and manifested by two hallmarks, the locking between the atomic spin and momentum and the dephasing in the Rabi oscillation. SO coupling in a periodic lattice renders topological matter. 1D Raman lattice show-cases a novel symmetry-protected topological (SPT) phase beyond the tenfold Altland-Zirnbauer classification. SPT phases distinguished by the Z2 invariant are determined from spin-textures. We highlight textures not only in equilibrium, but also of far-from-equilibrium dynamics after a quench between distinct phases, reflecting the band topology. Higher dimensional Raman lattices are richer. A three-dimensional (3D) topological nodal line semimetal structure has been observed for the first time with ultracold atoms, and reconstructed by a well-designed (pseudo-)tomography - extraction of Dirac points on different momentum layers, owing to the emergence of a crystalline symmetry. Similarly, topological features, such as band inversion lines that are bulk counterparts of Fermi arc states and connect Dirac points, are also uncovered from quench dynamics. "More is different." The SU(N) symmetric spin-independent interaction is investigated by Tan's contact and collective modes. Enhanced by the (orbital) Feshbach resonance, the Raman lattice with tunable interactions can be applied to engineer elusive topological many-body phases, which is envisaged for unveiling the attractive topological superfuilds.
This thesis reports on the experimental realization of the 3D SU(N) Fermi-Hubbard model and the direct probing of the equation of state with an ultracold quantum gas of fermionic ytterbium in an optical lattice. Ultracold atoms in optical lattices constitute a flexible and highly tunable system to investigate Hamiltonians of condensed matter physics such as the Hubbard model. In particular, ytterbium atoms are ideal candidates for the realization of the Fermi-Hubbard model with SU(N)-symmetry due to a high decoupling of the nuclear spin from the electronic configuration. As a consequence of this enlarged symmetry, thermodynamic properties of the atomic sample depend on N, the number of spin components in the quantum gas, and novel, exotic phases are predicted to emerge at low temperatures. By locally probing a quantum gas of 173Yb in a 3D optical lattice, we determine the equation of state of the SU(6) and SU(3) Fermi-Hubbard model. The measurement of the equation of state allows us to obtain direct, model-independent access to the thermodynamic quantities of the lattice gas. In this way, we can characterize the crossover from a Fermi liquid to an SU(N) Mott insulator when tuning the interaction strength, and can probe the compressibility of the quantum gas in different interaction regimes. Moreover, we find a low specific entropy of the SU(6) gas below that of uncorrelated spins, indicating the presence of partial spin correlations in the atomic sample. The ability to access the equation of state of such high spin systems, as well as the low obtained entropy, represent an important step towards the realization of SU(N) spin Hamiltonians and the characterization of novel SU(N) phases.
Ultracold quantum degenerate gases of alkaline-earth-like atoms open up new perspectives for the investigation of strongly-correlated many-body physics. Long-lived metastable states in combination with a decoupled nuclear spin enable the realization of intriguing Hamiltonians beyond the possibilities of current alkali-based experiments, ranging from the Kondo lattice model to SU(N)-symmetric magnetic systems. Among the alkaline-earth-like elements, Yb is particularly versatile due to its large number of bosonic and fermionic isotopes with a wide range of interaction strengths. This thesis describes a newly-built setup for the study of quantum manybody physics with ultracold Yb, demonstrating the preparation of Bose-Einstein condensates and multi-component degenerate Fermi gases in an optical lattice with coherent control over the electronic state.
Within this work we have implemented for the first time a two-dimensional magneto-optical trap (2D-MOT) for the initial laser cooling of Yb. The slow atoms from the 2D-MOT can directly be loaded into a 3D-MOT operating on a narrow intercombination transition, and loading rates comparable with Zeeman slower setups are achieved. The flexibility and the compact setup of the 2D-MOT makes our setup well suited for the production of multi-element quantum gas mixtures in the future.
Via evaporative cooling in a crossed optical dipole trap Bose-Einstein condensates of 174Yb with up to 2x10^5 atoms are produced. Loading the condensate into a triangular optical lattice, we observe the superfluid to Mott-insulator transition with Yb. Using the fermionic isotope 173Yb, quantum degenerate, multi-component Fermi gases with one to six spin components are obtained with up to 8x10^4 atoms at 15% of the Fermi temperature.
In order to coherently prepare Yb quantum gases in the metastable 3P0 state, an ultrastable laser addressing the 1S0-3P0 clock transition at 578nm has been developed as a major part of this thesis. Exhibiting a short-term stability at the 1Hz-level, this laser will serve as an important tool for the manipulation and probing of strongly-correlated many-body systems of ultracold Yb.
Control over the electronic state is demonstrated by Rabi spectroscopy on the 1S0-3P0 transition of quantum degenerate 173Yb in a three-dimensional optical lattice. In a spin-polarized sample more than 90% of the atoms can be prepared in the metastable 3P0 state. Driving a vibrational sideband transition, the atoms can also be coherently excited to higher bands in the optical lattice. Moreover, first experiments towards the electronic state control of interacting spin mixtures are performed, exhibiting signatures of interaction-induced lineshifts.
The preparation and manipulation techniques presented in this thesis constitute an important step towards the exploration of novel quantum many-body physics with ultracold Yb.
Ultrakalte Quantengase aus Erdalkali-ahnlichen Atomen eroffnen neue Moglichkeiten zur Untersuchung stark korrelierter Quantenvielteilchensysteme. Langlebige metastabile Zustande kombiniert mit einem entkoppelten Kernspin ermoglichen es faszinierende Vielteilchensysteme zu realisieren, die uber die Moglichkeiten heutiger Alkali-basierter Experimente hinausgehen: Vom Kondo-Gitter-Modell bis hin zu SU(N)-symmetrischen magnetischen Systemen. Von allen Erdalkali-ahnlichen Elementen besticht vor allem Ytterbium (Yb) durch die Vielzahl von fermionischen und bosonischen Isotopen mit unterschiedlichen Wechselwirkungsstarken. Im Rahmen der vorliegenden Arbeit wurde ein neuer experimenteller Aufbau zur Erforschung von Quantenvielteilchensystemen aus ultrakalten Yb-Atomen realisiert. Mit diesem Aufbau wurden sowohl Bose-Einstein Kondensate, als auch mehrkomponentige Fermigase in einem optischen Gitter prapariert. Ferner wurde die koharente Kontrolle des elektronischen Zustands ultrakalter Atome demonstriert.
In dem hier vorgestellten Aufbau wurde zum ersten Mal eine zweidimensionale magnetooptische Falle (2D-MOT) zur Erzeugung langsamer Yb-Atome implementiert. Die Atome aus der 2D-MOT konnen direkt in eine 3D-MOT auf einer schmalen Interkombinationslinie geladen werden. Die erzielten Laderaten sind mit denen von Zeeman slowern vergleichbar. Durch die Flexibilitat und den kompakten Aufbau der 2D-MOT ist unsere Apparatur besonders gut fur die Erzeugung mehrelementiger Quantengasmischungen in zukunftigen Experimenten geeignet.
Mittels evaporativer Kuhlung in einer gekreuzten Dipolfalle wurden reine 174Yb Bose-Einstein Kondensate mit bis zu 2x10^5 Atomen realisiert. Anhand dieser Kondensate konnte der Mott-Isolator Ubergang in einem optischen Dreiecksgitter demonstriert werden. Des Weiteren wurden unter Verwendung des fermionischen Isotops 173Yb ein- bis sechskomponentige quantenentartete
Fermigase mit bis zu 8x10^4 Atomen bei 15% der Fermitemperatur erzeugt.
Zur koharenten Praparation von Yb-Quantengasen im metastabilen 3P0-Zustand wurde als wichtiger Teil dieser Arbeit ein hochstabiler Laser fur die Anregung des 1S0-3P0 Uhrenubergangs bei 578nm entwickelt. Mit einer Kurzzeitstabilitat von etwa 1 Hz eroffnet dieser Laser vielfaltige Moglichkeiten der gezielten Manipulation und Detektion von ultrakalten Yb-Vielteilchensystemen.
Die Kontrolle des elektronischen Zustands wurde anhand von Rabi-Spektroskopie auf dem 1S0-3P0 Ubergang von quantenentartetem 173Yb in einem dreidimensionalen optischen Gitter gezeigt. In einem Spin-polarisierten Ensemble konnen mehr als 90% der Atome im metastabilen
3P0 prapariert werden. Die koharente Anregung in hohere Bander des optischen Gitters ist durch die Adressierung von Vibrationsseitenbandern moglich. Schlieslich wurden erste Experimente zur Kontrolle des elektronischen Zustands in wechselwirkenden Spin-Mischungen durchgefuhrt. Diese weisen Anzeichen von wechselwirkungsinduzierten Linienverschiebungen auf.
Die in dieser Arbeit vorgestellten Praparations- und Manipulationstechniken stellen einen guten Ausgangspunkt dar, um die neuartige Physik von Yb-Quantengasen zu untersuchen.