7 research outputs found
Extraordinary magnetic response of an anisotropic 2D antiferromagnet via site-dilution
A prominent character of two-dimensional magnetic systems is the enhanced
spin fluctuations, which however reduce the ordering temperature. Here we
report that a magnetic field of only one-thousandth of the Heisenberg
superexchange interaction can induce a crossover, which for practical purposes
is the effective ordering transition, at temperatures about 6 times of the Neel
transition in a site-diluted two-dimensional anisotropic quantum
antiferromagnet. Such a strong magnetic response is enabled because the system
directly enters the antiferromagnetically ordered state from the isotropic
disordered state skipping the intermediate anisotropic stage. The underlying
mechanism is achieved on a pseudospin-half square lattice realized in the
[(SrIrO3)1/(SrTiO3)2] superlattice thin film that is designed to linearly
couple the staggered magnetization to external magnetic fields by virtue of the
rotational symmetry-preserving Dzyaloshinskii Moriya interaction. Our model
analysis shows that the skipping of the anisotropic regime despite the finite
anisotropy is due to the enhanced isotropic fluctuations under moderate
dilution
Quasi-2D anomalous Hall Mott insulator of topologically engineered Jeff =1/2 electrons
We investigate an experimental toy-model system of a pseudospin-half
square-lattice Hubbard Hamiltonian in [(SrIrO3)1/(CaTiO3)1] to include both
nontrivial complex hopping and moderate electronic correlation. While the
former induces electronic Berry phases as anticipated from the weak-coupling
limit, the later stabilizes an antiferromagnetic (AFM) Mott insulator ground
state in analogous to the strong-coupling limit. Their combined results in the
real system are found to be an anomalous Hall effect with a non-monotonic
temperature dependence due to the self-competition of the electron-hole pairing
in the Mott state, and an exceptionally large Ising anisotropy that is captured
as a giant magnon gap beyond the superexchange approach. The unusual phenomena
highlight the rich interplay of electronic topology and electronic correlation
in the intermediate-coupling regime that is largely unexplored and challenging
in theoretical modelling.Comment: Accepted by Phys. Rev.
Strain-modulated Slater-Mott crossover of pseudospin-half square-lattice in (SrIrO3)1/ (SrTiO3)1 superlattices
We report on the epitaxial strain-driven electronic and antiferromagnetic
modulations of a pseudospin-half square lattice realized in superlattices of
(SrIrO3)1/(SrTiO3)1. With increasing compressive strain, we find the
low-temperature insulating behavior to be strongly suppressed with a
corresponding systematic reduction of both the Neel temperature and the
staggered moment. However, despite such a suppression, the system remains
weakly insulating above the Neel transition. The emergence of metallicity is
observed under large compressive strain but only at temperatures far above the
N\'eel transition. These behaviors are characteristics of the Slater-Mott
crossover regime, providing a unique experimental model system of the spin-half
Hubbard Hamiltonian with a tunable intermediate coupling strength
<i>In Situ</i> Nanoscale Characterization of Water Penetration through Plasma Polymerized Coatings
The
search continues for means of making quick determinations of
the efficacy of a coating for protecting a metal surface against corrosion.
One means of reducing the time scale needed to differentiate the performance
of different coatings is to draw from nanoscale measurements inferences
about macroscopic behavior. Here we connect observations of the penetration
of water into plasma polymerized (PP) protective coatings and the
character of the interface between the coating and an oxide-coated
aluminum substrate or model oxide-coated silicon substrate to the
macroscopically observable corrosion for those systems. A plasma polymerized
film from hexamethylÂdisiloxane (HMDSO) monomer is taken as illustrative
of a hydrophobic coating, while a PP film from maleic anhydride (MA)
is used as a characteristically hydrophilic coating. The neutron reflectivity
(NR) of films on silicon oxide coated substrates shows that water
moves more readily through the hydrophilic PP–MA film. Off-specular
X-ray scattering indicates the PP–MA film on aluminum is less
conformal with the substrate than is the PP–HMDSO film. Measurements
with infrared–visible sum frequency generation spectroscopy
(SFG), which probes the chemical nature of the interface, make clear
that the chemical interactions between coating and aluminum oxide
are disrupted by interfacial water. With this water penetration and
interface disruption, macroscopic corrosion can occur much more rapidly.
An Al panel coated with PP–MA corrodes after 1 day in salt
spray, while a similarly thin (∼30 nm) PP–HMDSO coating
protects an Al panel for a period on the order of one month
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Strain-Modulated Slater-Mott Crossover of Pseudospin-Half Square-Lattice in (SrIrO_{3})_{1}/(SrTiO_{3})_{1} Superlattices.
We report on the epitaxial strain-driven electronic and antiferromagnetic modulations of a pseudospin-half square-lattice realized in superlattices of (SrIrO_{3})_{1}/(SrTiO_{3})_{1}. With increasing compressive strain, we find the low-temperature insulating behavior to be strongly suppressed with a corresponding systematic reduction of both the Néel temperature and the staggered moment. However, despite such a suppression, the system remains weakly insulating above the Néel transition. The emergence of metallicity is observed under large compressive strain but only at temperatures far above the Néel transition. These behaviors are characteristics of the Slater-Mott crossover regime, providing a unique experimental model system of the spin-half Hubbard Hamiltonian with a tunable intermediate coupling strength
Recommended from our members
Strain-Modulated Slater-Mott Crossover of Pseudospin-Half Square-Lattice in (SrIrO_{3})_{1}/(SrTiO_{3})_{1} Superlattices.
We report on the epitaxial strain-driven electronic and antiferromagnetic modulations of a pseudospin-half square-lattice realized in superlattices of (SrIrO_{3})_{1}/(SrTiO_{3})_{1}. With increasing compressive strain, we find the low-temperature insulating behavior to be strongly suppressed with a corresponding systematic reduction of both the Néel temperature and the staggered moment. However, despite such a suppression, the system remains weakly insulating above the Néel transition. The emergence of metallicity is observed under large compressive strain but only at temperatures far above the Néel transition. These behaviors are characteristics of the Slater-Mott crossover regime, providing a unique experimental model system of the spin-half Hubbard Hamiltonian with a tunable intermediate coupling strength