10 research outputs found
Thermalization of Interacting Fermions and Delocalization in Fock space
By means of exact diagonalization, we investigate the onset of 'eigenstate
thermalization' and the crossover to ergodicity in a system of 1D fermions with
increasing interaction. We show that the fluctuations in the expectation values
of the momentum distribution from eigenstate to eigenstate decrease with
increasing coupling strength and system size. It turns out that these
fluctuations are proportional to the inverse participation ratio of eigenstates
represented in the Fock basis. We demonstrate that eigenstate thermalization
should set in even for vanishingly small perturbations in the thermodynamic
limit.Comment: 4 pages, 4 figure
Localized phase structures growing out of quantum fluctuations in a quench of tunnel-coupled atomic condensates
We investigate the relative phase between two weakly interacting 1D
condensates of bosonic atoms after suddenly switching on the tunnel-coupling.
The following phase dynamics is governed by the quantum sine-Gordon equation.
In the semiclassical limit of weak interactions, we observe the parametric
amplification of quantum fluctuations leading to the formation of breathers
with a finite lifetime. The typical lifetime and density of the these
'quasibreathers' are derived employing exact solutions of the classical
sine-Gordon equation. Both depend on the initial relative phase between the
condensates, which is considered as a tunable parameter.Comment: 7 pages, 5 figure
Electron-Plasmon scattering in chiral 1D systems with nonlinear dispersion
We investigate systems of spinless one-dimensional chiral fermions realized,
e.g., in the arms of electronic Mach-Zehnder interferometers, at high energies.
Taking into account the curvature of the fermionic spectrum and a finite
interaction range, we find a new scattering mechanism where high-energy
electrons scatter off plasmons (density excitations). This leads to an
exponential decay of the single-particle Green's function even at zero
temperature with an energy-dependent rate. As a consequence of this
electron-plasmon scattering channel, we observe the coherent excitation of a
plasmon wave in the wake of a high-energy electron resulting in the buildup of
a monochromatic sinusoidal density pattern.Comment: 5 pages, 3 figures; version as publishe
Self-induced oscillations in an optomechanical system
We have explored the nonlinear dynamics of an optomechanical system
consisting of an illuminated Fabry-Perot cavity, one of whose end-mirrors is
attached to a vibrating cantilever. Such a system can experience negative
light-induced damping and enter a regime of self-induced oscillations. We
present a systematic experimental and theoretical study of the ensuing
attractor diagram describing the nonlinear dynamics, in an experimental setup
where the oscillation amplitude becomes large, and the mirror motion is
influenced by several optical modes. A theory has been developed that yields
detailed quantitative agreement with experimental results. This includes the
observation of a regime where two mechanical modes of the cantilever are
excited simultaneously.Comment: 4.5 pages, 3 figures (v2: corrected few typos
Universal dephasing in a chiral 1D interacting fermion system
We consider dephasing by interactions in a one-dimensional chiral fermion
system (e.g. a Quantum Hall edge state). For finite-range interactions, we
calculate the spatial decay of the Green's function at fixed energy, which sets
the contrast in a Mach-Zehnder interferometer. Using a physically transparent
semiclassical ansatz, we find a power-law decay of the coherence at high
energies and zero temperature (T=0), with a universal asymptotic exponent of 1,
independent of the interaction strength. We obtain the dephasing rate at T>0
and the fluctuation spectrum acting on an electron.Comment: 5 pages, 3 figures; minor changes, version as published