Relaxation dynamics of an isolated large-spin Fermi gas far from equilibrium

A fundamental question in many-body physics is how closed quantum systems reach equilibrium. We address this question experimentally and theoretically in an ultracold large-spin Fermi gas where we find a complex interplay between internal and motional degrees of freedom. The fermions are initially prepared far from equilibrium with only a few spin states occupied. The subsequent dynamics leading to redistribution among all spin states is observed experimentally and simulated theoretically using a kinetic Boltzmann equation with full spin coherence. The latter is derived microscopically and provides good agreement with experimental data without any free parameters. We identify several collisional processes, which occur on different time scales. By varying density and magnetic field, we control the relaxation dynamics and are able to continuously tune the character of a subset of spin states from an open to a closed system.Comment: 18 pages, 9 figure

Engineering spin waves in a high-spin ultracold Fermi gas

We report on the detailed study of multi-component spin-waves in an s=3/2 Fermi gas where the high spin leads to novel tensorial degrees of freedom compared to s = 1/2 systems. The excitations of a spin-nematic state are investigated from the linear to the nonlinear regime, where the tensorial character is particularly pronounced. By tuning the initial state we engineer the tensorial spin-wave character, such that the magnitude and sign of the counterflow spin-currents are effectively controlled. A comparison of our data with numerical and analytical results shows excellent agreement.Comment: 9 pages, 4 figure

Coherent multi-flavour spin dynamics in a fermionic quantum gas

Microscopic spin interaction processes are fundamental for global static and dynamical magnetic properties of many-body systems. Quantum gases as pure and well isolated systems offer intriguing possibilities to study basic magnetic processes including non-equilibrium dynamics. Here, we report on the realization of a well-controlled fermionic spinor gas in an optical lattice with tunable effective spin ranging from 1/2 to 9/2. We observe long-lived intrinsic spin oscillations and investigate the transition from two-body to many-body dynamics. The latter results in a spin-interaction driven melting of a band insulator. Via an external magnetic field we control the system's dimensionality and tune the spin oscillations in and out of resonance. Our results open new routes to study quantum magnetism of fermionic particles beyond conventional spin 1/2 systems.Comment: 9 pages, 5 figure

Momentum-Resolved Bragg Spectroscopy in Optical Lattices

Strongly correlated many-body systems show various exciting phenomena in condensed matter physics such as high-temperature superconductivity and colossal magnetoresistance. Recently, strongly correlated phases could also be studied in ultracold quantum gases possessing analogies to solid-state physics, but moreover exhibiting new systems such as Fermi-Bose mixtures and magnetic quantum phases with high spin values. Particularly interesting systems here are quantum gases in optical lattices with fully tunable lattice and atomic interaction parameters. While in this context several concepts and ideas have already been studied theoretically and experimentally, there is still great demand for new detection techniques to explore these complex phases in detail. Here we report on measurements of a fully momentum-resolved excitation spectrum of a quantum gas in an optical lattice by means of Bragg spectroscopy. The bandstructure is measured with high resolution at several lattice depths. Interaction effects are identified and systematically studied varying density and excitation fraction.Comment: 13 pages, 5 figure

Optical metrology terminal for satellite-to-satellite laser ranging

Interferometric laser ranging is an enabling technology for high-precision satellite-to-satellite tracking within the context of earth observation, gravitational wave detection, or formation flying. In orbit, the measurement system is affected by environmental influences, particularly satellite attitude jitter and temperature fluctuations, demanding an instrument design, which has a high level of thermal stability and is insensitive to rotations around the satellite's center of mass. Different design approaches for a heterodyne dynamic laser ranging instrument have been combined to a new improved design concept that involves the inherent beam tracking capabilities of a retroreflector into a mono-axial configuration with nanometer accuracy. In order to facilitate the accommodation onboard a future satellite mission, the design allows for a continuously adjustable flexible phase center position. To cover large inter-spacecraft distances, the instrument design comprises an active transponder system, featuring a two-dimensional beam steering mechanism to align a local, strong laser to the (weak) input beam without affecting the measurement path. To this end, a dynamic laser ranging instrument is presented, which has compact dimensions and is fully integrated on a single Zerodur baseplate. The instrument performance will be evaluated in a dedicated test setup providing a flat-top beam simulating the laser beam received from a distant spacecraft, including a beam steering subsystem, which allows for monitoring of pathlength variations when the angle of incidence at the optical instrument is changing

Architecture and performance analysis of an optical metrology terminal for satellite-to-satellite laser ranging

Interferometric laser ranging is an enabling technology for high-precision satellite-to-satellite tracking within the context of earth observation, gravitational wave detection, or formation flying. In orbit, the measurement system is affected by environmental influences, particularly satellite attitude jitter and temperature fluctuations, imposing an instrument design with a high level of thermal stability and insensitivity to rotations around the spacecraft center of mass. The new design concept presented here combines different approaches for dynamic heterodyne laser ranging and features the inherent beam tracking capabilities of a retroreflector in a mono-axial configuration. It allows for a continuously adjustable distance between the optical bench and the location of its fiducial point, facilitating future inter-satellite tracking with nanometer accuracy, e.g., the next-generation gravity mission