47 research outputs found
Light induced magnetization in a spin S=1 easy-plane antiferromagnetic chain
The time evolution of magnetization induced by circularly polarized light in
a Heisenberg chain with large, easy--plane anisotropy is studied
numerically and analytically. Results at constant light frequency
are interpreted in terms of absorption lines of the
electronic spin resonance spectrum. Applying a time dependent light frequency
, so called chirping, is shown to be an efficient procedure
in order to obtain within a short time a large, controlled value of the
magnetization . Furthermore, comparison with a - level model provides
a qualitative understanding of the induced magnetization process
Eigenstate thermalization within isolated spin-chain systems
The thermalization phenomenon and many-body quantum statistical properties
are studied on the example of several observables in isolated spin-chain
systems, both integrable and generic non-integrable ones. While diagonal matrix
elements for non-integrable models comply with the eigenstate thermalization
hypothesis (ETH), the integrable systems show evident deviations and similarity
to properties of noninteracting many-fermion models. The finite-size scaling
reveals that the crossover between two regimes is given by a scale closely
related to the scattering length. Low-frequency off-diagonal matrix elements
related to d.c. transport quantities in a generic system also follow the
behavior analogous to the ETH, however unrelated to the one of diagonal
elements
Coexistence of Anomalous and Normal Diffusion in Integrable Mott Insulators
We study the finite-momentum spin dynamics in the one-dimensional XXZ spin
chain within the Ising-type regime at high temperatures using density
autocorrelations within linear response theory and real-time propagation of
nonequilibrium densities. While for the nonintegrable model results are well
consistent with normal diffusion, the finite-size integrable model unveils the
coexistence of anomalous and normal diffusion in different regimes of time. In
particular, numerical results show a Gaussian relaxation at smallest nonzero
momenta which we relate to nonzero stiffness in a grand canonical ensemble. For
larger but still small momenta normal-like diffusion is recovered. Similar
results for the model of impenetrable particles also help to resolve rather
conflicting conclusions on transport in integrable Mott insulators.Comment: 5 pages, 4 figure