640 research outputs found
Uncovering the mechanism of the impurity-selective Mott transition in paramagnetic VO
While the phase diagrams of the one- and multi-orbital Hubbard model have
been well studied, the physics of real Mott insulators is often much richer,
material dependent, and poorly understood. In the prototype Mott insulator
VO, chemical pressure was initially believed to explain why the
paramagnetic-metal to antiferromagnetic-insulator transition temperature is
lowered by Ti doping while Cr doping strengthens correlations, eventually
rendering the high-temperature phase paramagnetic insulating. However, this
scenario has been recently shown both experimentally and theoretically to be
untenable. Based on full structural optimization, we demonstrate via the charge
self-consistent combination of density functional theory and dynamical
mean-field theory that changes in the VO phase diagram are driven
by defect-induced local symmetry breakings resulting from dramatically
different couplings of Cr and Ti dopants to the host system. This finding
emphasizes the high sensitivity of the Mott metal-insulator transition to the
local environment and the importance of accurately accounting for the
one-electron Hamiltonian, since correlations crucially respond to it.Comment: 5 pages, 5 figures, supplementary informatio
The spin alignment of galaxies with the large-scale tidal field in hydrodynamic simulations
The correlation between the spins of dark matter halos and the large-scale
structure (LSS) has been studied in great detail over a large redshift range,
while investigations of galaxies are still incomplete. Motivated by this point,
we use the state-of-the-art hydrodynamic simulation, Illustris-1, to
investigate mainly the spin--LSS correlation of galaxies at redshift of .
We mainly find that the spins of low-mass, blue, oblate galaxies are
preferentially aligned with the slowest collapsing direction () of the
large-scale tidal field, while massive, red, prolate galaxy spins tend to be
perpendicular to . The transition from a parallel to a perpendicular trend
occurs at in the stellar mass, in the g-r
color, and in triaxiality. The transition stellar mass decreases with
increasing redshifts. The alignment was found to be primarily correlated with
the galaxy stellar mass. Our results are consistent with previous studies both
in N-body simulations and observations. Our study also fills the vacancy in the
study of the galaxy spin--LSS correlation at using hydrodynamical
simulations and also provides important insight to understand the formation and
evolution of galaxy angular momentum.Comment: 9 pages, 6 figures, 1 table. Accepted for publication in ApJ, match
the proof versio
Filaments from the galaxy distribution and from the velocity field in the local universe
The cosmic web that characterizes the large-scale structure of the Universe
can be quantified by a variety of methods. For example, large redshift surveys
can be used in combination with point process algorithms to extract long
curvilinear filaments in the galaxy distribution. Alternatively, given a full
3D reconstruction of the velocity field, kinematic techniques can be used to
decompose the web into voids, sheets, filaments and knots. In this paper we
look at how two such algorithms - the Bisous model and the velocity shear web -
compare with each other in the local Universe (within 100 Mpc), finding good
agreement. This is both remarkable and comforting, given that the two methods
are radically different in ideology and applied to completely independent and
different data sets. Unsurprisingly, the methods are in better agreement when
applied to unbiased and complete data sets, like cosmological simulations, than
when applied to observational samples. We conclude that more observational data
is needed to improve on these methods, but that both methods are most likely
properly tracing the underlying distribution of matter in the Universe.Comment: 6 Pages, 2 figures, Submitted to MNRAS Letter
- …