52 research outputs found
Stable -th capillary hypersurfaces
In this paper, we propose a new definition of stable -th capillary
hypersurfaces from variational perspective for any . More
precisely, we define stable -th capillary hypersurfaces to be smooth
local minimizers of a new energy functional under volume-preserving and contact
angle-preserving variations. Using the new concept of the stable -th
capillary hypersurfaces, we generalize the stability results of Souam
\cite{Souam} in an Euclidean half-space and Guo-Wang-Xia \cite{GWX} in a
horoball in hyperbolic space for capillary hypersurface to -th capillary
hypersurface case.Comment: 31 pages,2 figure
Doping and dimensionality effects on the core-level spectra of layered ruthenates
Core-level spectra of the Mn-doped Sr3Ru2O7 and Srn+1RunO3n+1 (n = 1, 2 and
3) crystals are investigated with X-ray photoelectron spectroscopy. Doping of
Mn to Sr3Ru2O7 considerably affects the distribution of core-level spectral
weight. The satellite of Ru 3d core levels exhibits a substantial change with
doping, indicating an enhanced electron localization across the doping- induced
metal-insulator transition. However, the Ru 3p core levels remain identical
with Mn-doping, thus showing no sign of doping-induced multiple Ru valences. In
the Srn+1RunO3n+1 (n = 1, 2 and 3), the Ru 3d core-level spectra are similar,
indicating that the chemical bonding environment around Ru ions remains the
same for different layered compounds. Meanwhile the Sr 3d shallow core levels
shift to higher binding energy with increasing n, suggesting their
participation in Sr-O bonding with structural evolution.Comment: 6 pages with 6 figures, to be published in PR
Giant photoinduced lattice distortion in oxygen-vacancy ordered SrCoO2.5 thin films
Despite of the tremendous efforts spent on the oxygen vacancy migration in
determining the property optimization of oxygen-vacancy enrichment transition
metal oxides, few has focused on their dynamic behaviors non-equilibrium
states. In this work, we performed multi-timescale ultrafast X-ray diffraction
measurements by using picosecond synchrotron X-ray pulses and femtosecond
table-top X-ray pulses to monitor the structural dynamics in the oxygen-vacancy
ordered SrCoO2.5 thin films. A giant photoinduced strain ({\Delta}c/c > 1%) was
observed, whose distinct correlation with the pump photon energy indicates a
non-thermal origin of the photoinduced strain. The sub-picosecond resolution
X-ray diffraction reveals the formation and propagation of the coherent
acoustic phonons inside the film. We also simulate the effect of photoexcited
electron-hole pairs and the resulting lattice changes using the Density
Function Theory method to obtain further insight on the microscopic mechanism
of the measured photostriction effect. Comparable photostrictive responses and
the strong dependence on excitation wavelength are predicted, revealing a
bonding to anti-bonding charge transfer or high spin to intermediate spin
crossover induced lattice expansion in the oxygen-vacancy films.Comment: 12 pages, 4 figures, support materia
Exploration of growth conditions of TaAs Weyl semimetal thin film by pulsed laser deposition
TaAs, the first experimentally discovered Weyl semimetal material, has
attracted a lot of attention due to its high carrier mobility, high anisotropy,
nonmagnetic and strong interaction with light. These make it an ideal candidate
for the study of Weyl fermions and the applications in quantum computation,
thermoelectric devices, and photodetection. For further basic physics studies
and potential applications, large-size and high-quality TaAs films are urgently
needed. However, it is difficult to grow As-stoichiometry TaAs films due to the
volatilization of As during the growth. To solve this problem, the TaAs films
were attempted to grow on different substrates using targets with different As
stoichiometric ratios by pulsed laser deposition (PLD). In this work, we have
found that partial As ions of the GaAs substrate are likely to diffuse into the
TaAs films during growth, which was preliminarily confirmed by the structural
characterization, surface topography and composition analysis. As a result, the
As content in the TaAs film is improved and the TaAs phase is achieved. Our
work presents an effective method to fabricate the TaAs films by PLD, providing
the possible use of the Weyl semimetal film for functional devices
Manipulating Multiple Order Parameters via Oxygen Vacancies: The case of Eu0.5Ba0.5TiO3-{\delta}
Controlling functionalities, such as magnetism or ferroelectricity, by means
of oxygen vacancies (VO) is a key issue for the future development of
transition metal oxides. Progress in this field is currently addressed through
VO variations and their impact on mainly one order parameter. Here we reveal a
new mechanism for tuning both magnetism and ferroelectricity simultaneously by
using VO. Combined experimental and density-functional theory studies of
Eu0.5Ba0.5TiO3-{\delta}, we demonstrate that oxygen vacancies create Ti3+ 3d1
defect states, mediating the ferromagnetic coupling between the localized Eu
4f7 spins, and increase an off-center displacement of Ti ions, enhancing the
ferroelectric Curie temperature. The dual function of Ti sites also promises a
magnetoelectric coupling in the Eu0.5Ba0.5TiO3-{\delta}.Comment: Accepted by Physical Review B, 201
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