5 research outputs found
Spin-density fluctuations and the fluctuation-dissipation theorem in 3d ferromagnetic metals
Spatial and time scales of spin density fluctuations (SDF) were analyzed in
3d ferromagnets using ab initio linear response calculations of complete
wavevector and energy dependence of the dynamic spin susceptibility tensor. We
demonstrate that SDF are spread continuously over the entire Brillouin zone and
while majority of them reside within the 3d bandwidth, a significant amount
comes from much higher energies. A validity of the adiabatic approximation in
spin dynamics is discussed. The SDF spectrum is shown to have two main
constituents: a minor low-energy spin wave contribution and a much larger
high-energy component from more localized excitations. Using the
fluctuation-dissipation theorem (FDT), the on-site spin correlator (SC) and the
related effective fluctuating moment were properly evaluated and their
universal dependence on the 3d band population is further discussed
Sub-cycle multidimensional spectroscopy of strongly correlated materials
Strongly correlated solids are extremely complex and fascinating quantum
systems, where new states continue to emerge, especially when interaction with
light triggers interplay between them. In this interplay, sub-laser-cycle
electron response is particularly attractive as a tool for ultrafast
manipulation of matter at PHz scale. Here we introduce a new type of non-linear
multidimensional spectroscopy, which allows us to unravel the sub-cycle
dynamics of strongly correlated systems interacting with few-cycle infrared
pulses and the complex interplay between different correlated states evolving
on the sub-femtosecond time-scale. We demonstrate that single particle
sub-cycle electronic response is extremely sensitive to correlated many-body
dynamics and provides direct access to many body response functions. For the
two-dimensional Hubbard model under the influence of ultra-short, intense
electric field transients, we demonstrate that our approach can resolve
pathways of charge and energy flow between localized and delocalized many-body
states on the sub-cycle time scale and follow the creation of a highly
correlated state surviving after the end of the laser pulse. Our findings open
a way towards a regime of imaging and manipulating strongly correlated
materials at optical rates, beyond the multi-cycle approach employed in Floquet
engineering, with the sub-cycle response being a key tool for accessing many
body phenomena.Comment: 10 pages, 4, figures, Methods (5 pages), Supplementary information (4
figures, 4 pages
Spin-density fluctuations and the fluctuation-dissipation theorem in 3d ferromagnetic metals
Spatial and time scales of spin-density fluctuations (SDFs) were analyzed in 3d ferromagnets using ab initio linear-response calculations of complete wave-vector and energy dependence of the dynamic spin susceptibility tensor. We demonstrate that SDFs are spread continuously over the entire Brillouin zone and while the majority of them reside within the 3d bandwidth, a significant amount comes from much higher energies. A validity of the adiabatic approximation in spin dynamics is discussed. The SDF spectrum is shown to have two main constituents: a minor low-energy spin-wave contribution and a much larger high-energy component from more localized excitations. Using the fluctuation-dissipation theorem, the on-site spin correlator and the related effective fluctuating moment were properly evaluated and their universal dependence on the 3d band population is further discussed.</p
Dynamically induced doublon repulsion in the Fermi-Hubbard model probed by a single-particle density of states
We investigate the possibility to control dynamically the interactions
between repulsively bound pairs of fermions (doublons) in correlated systems
with off-resonant ac fields. We introduce an effective Hamiltonian that
describes the physics of doublons up to the second-order in the high-frequency
limit. It unveils that the doublon interaction, which is attractive in
equilibrium, can be completely suppressed and then switched to repulsive by
varying the power of the ac field. We show that the signature of the dynamical
repulsion between doublons can be found in the single-fermion density of states
averaged in time. Our results are further supported by nonequilibrium dynamical
mean-field theory simulations for the half-filled Fermi-Hubbard model