767 research outputs found
Disorder versus two transport lifetimes in a strongly correlated electron liquid
We report on angle-dependent measurements of the sheet resistances and Hall
coefficients of electron liquids in SmTiO3/SrTiO3/SmTiO3 quantum well
structures, which were grown by molecular beam epitaxy on (001) DyScO3. We
compare their transport properties with those of similar structures grown on
LSAT [(La0.3Sr0.7)(Al0.65Ta0.35)O3]. On DyScO3, planar defects normal to the
quantum wells lead to a strong in-plane anisotropy in the transport properties.
This allows for quantifying the role of defects in transport. In particular, we
investigate differences in the longitudinal and Hall scattering rates, which is
a non-Fermi liquid phenomenon known as lifetime separation. The residuals in
both the longitudinal resistance and Hall angle were found to depend on the
relative orientations of the transport direction to the planar defects. The
Hall angle exhibited a robust T2 temperature dependence along all directions,
whereas no simple power law could describe the temperature dependence of the
longitudinal resistances. Remarkably, the degree of the carrier lifetime
separation, as manifested in the distinctly different temperature dependences
and diverging residuals near a critical quantum well thickness, was completely
insensitive to disorder. The results allow for a clear distinction between
disorder-induced contributions to the transport and intrinsic, non-Fermi liquid
phenomena, which includes the lifetime separation.Comment: In press, Sci. Re
Growth of strontium ruthenate films by hybrid molecular beam epitaxy
We report on the growth of epitaxial Sr2RuO4 films using a hybrid molecular
beam epitaxy approach in which a volatile precursor containing RuO4 is used to
supply ruthenium and oxygen. The use of the precursor overcomes a number of
issues encountered in traditional MBE that uses elemental metal sources.
Phase-pure, epitaxial thin films of Sr2RuO4 are obtained. At high substrate
temperatures, growth proceeds in a layer-by-layer mode with intensity
oscillations observed in reflection high-energy electron diffraction. Films are
of high structural quality, as documented by x-ray diffraction, atomic force
microscopy, and transmission electron microscopy. The method should be suitable
for the growth of other complex oxides containing ruthenium, opening up
opportunities to investigate thin films that host rich exotic ground states.Comment: In press, APL Mate
Response of the lattice across the filling-controlled Mott metal-insulator transition of a rare earth titanate
The lattice response of a prototype Mott insulator, SmTiO3, to hole doping is
investigated with atomic-scale spatial resolution. SmTiO3 films are doped with
Sr on the Sm site with concentrations that span the insulating and metallic
sides of the filling-controlled Mott metal-insulator transition (MIT). The
GdFeO3-type distortions are investigated using an atomic resolution scanning
transmission electron microscopy technique that can resolve small lattice
distortions with picometer precision. We show that these distortions are
gradually and uniformly reduced as the Sr concentration is increased without
any phase separation. Significant distortions persist into the metallic state.
The results present a new picture of the physics of this prototype
filling-controlled MIT, which is discussed.Comment: Accepted, Phys. Rev. Let
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Controlling a Van Hove singularity and Fermi surface topology at a complex oxide heterostructure interface.
The emergence of saddle-point Van Hove singularities (VHSs) in the density of states, accompanied by a change in Fermi surface topology, Lifshitz transition, constitutes an ideal ground for the emergence of different electronic phenomena, such as superconductivity, pseudo-gap, magnetism, and density waves. However, in most materials the Fermi level, [Formula: see text], is too far from the VHS where the change of electronic topology takes place, making it difficult to reach with standard chemical doping or gating techniques. Here, we demonstrate that this scenario can be realized at the interface between a Mott insulator and a band insulator as a result of quantum confinement and correlation enhancement, and easily tuned by fine control of layer thickness and orbital occupancy. These results provide a tunable pathway for Fermi surface topology and VHS engineering of electronic phases
Effects of radiative heat transfer on the structure of turbulent supersonic channel flow
International audienceThe interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport
Dynamical temperature study for classical planar spin systems
In this micro-canonical simulation the temperature and also the specific heat
are determined as averages of expressions easy to implement. The XY-chain is
studied for a test. The second order transition on a cubic lattice and the
first order transition on an fcc lattice are analyzed in greater detail to have
a more severe test about the feasibility of this micro-canonical method.Comment: 9 pages in Latex(revtex), 7 PS-figure
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