10 research outputs found
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
Measuring quantized circular dichroism in ultracold topological matter
info:eu-repo/semantics/publishe
Measuring quantized circular dichroism in ultracold topological matter
The topology of two-dimensional materials traditionally manifests itself through the quantization of the Hall conductance, which is revealed in transport measurements 1â3 .Recently, it was predicted that topology can also give rise to a characteristic spectroscopic response on subjecting a Chern insulator to a circular drive: comparing the frequency-integrated depletion rates associated with drives of opposite orientation leads to a quantized response dictated by the topological Chern number of the populated Bloch band 4,5 .Here we experimentally demonstrate this intriguing topological effect using ultracold fermionic atoms in topological Floquet bands. In addition, our depletion-rate measurements also provide an experimental estimation of the Wannier-spread functional, a fundamental geometric property of Bloch bands related to the quantum metric 6,7 .Our results establish topological spectroscopic responses as a versatile probe, which could be applied to access the geometry and topology of many-body quantum systems, such as fractional Chern insulators 8 .SCOPUS: le.jinfo:eu-repo/semantics/publishe