24 research outputs found
Efimov Physics in a three-component Fermi gas
This thesis reports on experiments studying the few-body physics of three distinguishable fermionic atoms with large scattering lengths. The experiments were performed with ultracold gases of fermionic 6Li atoms in three different hyperfine states. By tuning the strength of the interactions between the atoms with Feshbach resonances and measuring the rate constants for inelastic three-atom and atom-dimer collisions the intersections of two universal trimer states with the three-atom and atom-dimer continuum could be located. Subsequently, one of these Efimov states was directly observed with RF-association spectroscopy. Using this technique the binding energy of this Efimov state was measured as a function of the strength of the interparticle interactions. The experiments presented in this thesis provide a nearly complete understanding of the universal few-body physics of three-component Fermi gases of 6Li atoms. This understanding will be the foundation for future studies of the many-body physics of three-component Fermi gases
Radio Frequency Association of Efimov Trimers
The quantum-mechanical three-body problem is one of the fundamental
challenges of few-body physics. When the two-body interactions become resonant,
an infinite series of universal three-body bound states is predicted to occur,
whose properties are determined by the strength of the two-body interactions.
We report on the association and direct observation of a trimer state
consisting of three distinguishable fermions using radio-frequency (RF)
spectroscopy. The measurements of its binding energy are consistent with
theoretical predictions which include non-universal corrections.Comment: 12 pages, 6 figure
Antiferromagnetic Heisenberg Spin Chain of a Few Cold Atoms in a One-Dimensional Trap
We report on the deterministic preparation of antiferromagnetic Heisenberg
spin chains consisting of up to four fermionic atoms in a one-dimensional trap.
These chains are stabilized by strong repulsive interactions between the two
spin components without the need for an external periodic potential. We
independently characterize the spin configuration of the chains by measuring
the spin orientation of the outermost particle in the trap and by projecting
the spatial wave function of one spin component on single-particle trap levels.
Our results are in good agreement with a spin-chain model for fermionized
particles and with numerically exact diagonalizations of the full few-fermion
system
Sound propagation and quantum limited damping in a two-dimensional Fermi gas
Strongly interacting two-dimensional Fermi systems are one of the great
remaining challenges in many-body physics due to the interplay of strong local
correlations and enhanced long-range fluctuations. Here, we probe the
thermodynamic and transport properties of a 2D Fermi gas across the BEC-BCS
crossover by studying the propagation and damping of sound modes. We excite
particle currents by imprinting a phase step onto homogeneous Fermi gases
trapped in a box potential and extract the speed of sound from the frequency of
the resulting density oscillations. We measure the speed of sound across the
BEC-BCS crossover and compare the resulting dynamic measurement of the equation
of state both to a static measurement based on recording density profiles and
to Quantum Monte Carlo calculations and find reasonable agreement between all
three. We also measure the damping of the sound mode, which is determined by
the shear and bulk viscosities as well as the thermal conductivity of the gas.
We find that the damping is minimal in the strongly interacting regime and the
diffusivity approaches the universal quantum bound of a perfect
fluid