Transition In Sr Research Articles

Mobility of essential macro- and micro-elements in interaction between artificial sweat and potential peloids of some saline lakes in Mongolia

Abstract Individuals may experience health issues attributable to environmental pollution, sedentary lifestyles, and unhealthy dietary habits. In response, numerous non-pharmaceutical treatments and techniques have emerged, with therapy mud being one such approach. The primary aim of this research was to analyze the chemical and mineralogical compositions of peloids obtained from six salt lakes: Taigan (LI), Duruu (LII), Khadaasan (LIII), Ikhes (LIV), Tonkhil (LV), and Khulmaa (LVI) in the Gobi-Altai province of Mongolia. Sample analyses involved X-ray diffraction for mineralogical assessment and inductively coupled plasma-mass spectrometry (Agilent Technologies 7800 series in Canada) for determining the chemical composition of the solid phase. Among essential macro- and microelements, Mg, Cа, Na, K, Sr, Ga, Mo, and Se had been leached from peloid to artificial sweat. Sn (0.01 μg g–1) at LIV and LVI lakes and Cu (0.01 μg g–1) at LV lake transferred from peloids to sweat, but no mobility of these elements in other peloids was detected. Li (0.02–0.04 μg g–1) was adsorbed from the sweat to potential peloids in LV, LIV, LIII, and LI lakes, while As (0.04–0.09 μg g–1) leached from peloids to sweat in all lakes except for LII. Zn (0.01 μg g–1) and Cr (0.04 μg g–1) transferred from the sweat to peloids in all lakes. Macroelements (Na, K, Ca, and Mg) and microelements (Mo, Se), which are essential for the human body, leached from the peloid to sweat. However, the mobility of toxic elements was minimal. Among micro-elements, the transition of Sr occurred the most, which can be explained by the Sr content in the peloid.

Pressure-Induced Anion Order-Disorder Transition in Layered Perovskite Sr2LiHOCl2.

While cation order-disorder transitions have been extensively investigated because of their decisive impact on chemical and physical properties, only few anion order-disorder transitions are known. Here, we show that Sr2CuO2Cl2-type layered perovskite Sr2LiHOCl2 exhibits a pressure-induced H-/O2- order-disorder transition. When synthesized at ambient and low pressures (≤2 GPa), Sr2LiHOCl2 is isostructural to orthorhombic Eu2LiHOCl2 (Cmcm) with a H-/O2- order at the equatorial sites. However, applying a higher pressure (5 GPa) during synthesis causes the equatorial anions to be disordered, leading to a tetragonal symmetry (I4/mmm) with a loss of the superstructure. The structural analysis revealed that, in the ambient pressure phase, HLi2Sr4 and OLi2Sr4 octahedra have distinct sizes to stabilize otherwise underbonded oxide ions, which is less important at the higher pressure. Anion-disordered Sr2LiHOBr2 and Ba2LiHOCl2 were also obtained at 5 GPa. Given the abundant layer-type anion order in perovskite-based oxyhydrides (e.g., La2LiHO3), the inclusion of additional anions (e.g., chloride) expands the frontiers of anion ordering patterns and their distribution control with the benefit of improving ionic conduction in solids.

Evolution of the spectral lineshape at the magnetic transition in Sr$$_2$$IrO$$_4$$ and Sr$$_3$$Ir$$_2$$O$$_7$$

Sr $$_2$$ IrO $$_4$$ and Sr $$_3$$ Ir $$_2$$ O $$_7$$ form two families of spin-orbit Mott insulators with quite different charge gaps and an antiferromagnetic (AF) ground state. This offers a unique opportunity to study the impact of long-range magnetic order in Mott insulators. It appears to play a different role in the two families, as there is almost no change of the resistivity at the magnetic transition $$T_N$$ in Sr $$_2$$ IrO $$_4$$ and a large one in Sr $$_3$$ Ir $$_2$$ O $$_7$$ . We use angle-resolved photoemission to study the evolution of the spectral lineshape through the magnetic transition. We use Ru and La substitutions to tune $$T_N$$ and discriminate changes due to temperature from those due to magnetic order. We evidence a shift and a transfer of spectral weight in the gap at $$T_N$$ in Sr $$_3$$ Ir $$_2$$ O $$_7$$ , which is absent in Sr $$_2$$ IrO $$_4$$ . We assign this behavior to a significantly larger coherent contribution to the spectral lineshape in Sr $$_3$$ Ir $$_2$$ O $$_7$$ , which evolves strongly at $$T_N$$ . On the contrary, the Sr $$_2$$ IrO $$_4$$ lineshape is dominated by the incoherent part, which is insensitive to $$T_N$$ . We compare these findings to theoretical expectations of the Slater vs Mott antiferromagnetism within dynamical mean field theory.

Reflected entropy in random tensor networks. Part II. A topological index from canonical purification

In ref. [1], we analyzed the reflected entropy (SR) in random tensor networks motivated by its proposed duality to the entanglement wedge cross section (EW) in holographic theories, {S}_R=2frac{EW}{4G} . In this paper, we discover further details of this duality by analyzing a simple network consisting of a chain of two random tensors. This setup models a multiboundary wormhole. We show that the reflected entanglement spectrum is controlled by representation theory of the Temperley-Lieb algebra. In the semiclassical limit motivated by holography, the spectrum takes the form of a sum over superselection sectors associated to different irreducible representations of the Temperley-Lieb algebra and labelled by a topological index k ∈ ℤ>0. Each sector contributes to the reflected entropy an amount 2kfrac{EW}{4G} weighted by its probability. We provide a gravitational interpretation in terms of fixed-area, higher-genus multiboundary wormholes with genus 2k – 1 initial value slices. These wormholes appear in the gravitational description of the canonical purification. We confirm the reflected entropy holographic duality away from phase transitions. We also find important non-perturbative contributions from the novel geometries with k ≥ 2 near phase transitions, resolving the discontinuous transition in SR. Along with analytic arguments, we provide numerical evidence for our results. We finally speculate that signatures of a non-trivial von Neumann algebra, connected to the Temperley-Lieb algebra, will emerge from a modular flowed version of reflected entropy.

Microfabricated strontium atomic vapor cells.

We demonstrate strontium (Sr) atomic vapor cells having a total external volume of 0.63 cm3 that can operate above 300 °C for times exceeding 380 h. The cells are fabricated using micromachined silicon frames anodically bonded to glass windows that have a 20-nm thick protective layer of Al2O3 deposited on the interior surfaces. The presence of Sr vapor in the cell is confirmed through laser absorption spectroscopy for the 1S0 → 1P1 transition in Sr at 461 nm. Measurements of sub-Doppler linewidths indicated negligible (<3 MHz) broadening of this transition from residual background gas collisions. This compact and manufacturable, high-temperature atomic vapor cell can enable narrow-line optical frequency references based on strontium and other alkaline earth species.

Strong increase in ultrasound attenuation below Tc in Sr2RuO4 : Possible evidence for domains

Recent experiments suggest that the superconducting order parameter of Sr$_2$RuO$_4$ has two components. A two-component order parameter has multiple degrees of freedom in the superconducting state that can result in low-energy collective modes or the formation of domain walls -- a possibility that would explain a number of experimental observations including the smallness of the time reversal symmetry breaking signal at T$_\mathrm{c}$ and telegraph noise in critical current experiments. We perform ultrasound attenuation measurements across the superconducting transition of Sr$_2$RuO$_4$ using resonant ultrasound spectroscopy (RUS). We find that the attenuation for compressional sound increases by a factor of seven immediately below T$_\mathrm{c}$, in sharp contrast with what is found in both conventional ($s$-wave) and high-T$_\mathrm{c}$ ($d$-wave) superconductors. We find our observations to be most consistent with the presence of domain walls between different configurations of the superconducting state. The fact that we observe an increase in sound attenuation for compressional strains, and not for shear strains, suggests an inhomogeneous superconducting state formed of two distinct, accidentally-degenerate superconducting order parameters that are not related to each other by symmetry. Whatever the mechanism, a factor of seven increase in sound attenuation is a singular characteristic with which any potential theory of the superconductivity in Sr$_2$RuO$_4$ must be reconciled.

Revealing pressure-driven structural transitions in the hybrid improper ferroelectric Sr3Sn2O7

The authors bring together diamond anvil cell techniques, infrared spectroscopy, a symmetry analysis, and lattice dynamics calculations to reveal the series of pressure-induced structural phase transitions in the hybrid improper ferroelectric Sr${}_{3}$Sn${}_{2}$O${}_{7}$. Remarkably, the pressure and temperature progressions are identical, and this information is used to develop the phase diagram. Pressure and probably strain are highly advantageous for device applications in this family of materials because the entire series of transitions can be triggered at room temperature.

Ferroelectric Transition in Sr- and W-Doped BaTiO3 Solid Solutions

We synthesized Sr- and W-doped BaTiO3 (BTO) polycrystals by using a solid-state reaction method. The X-ray diffraction results showed that Sr and W atoms occupied the Ba and Ti sites in tetragonal BTO, respectively, and there were changes in the lattice constants and the volumes in the Sr- and W-doped BTO. We found a change in the latent heat and the Curie temperature (TC) during the transition between the ferroelectric and paraelectric phases while increasing the contents of Sr and W in the Sr- and W-doped BTO. This can be explained by the fact that the doping of Sr and W atoms in BTO prevented a distinct transition between the ferroelectric tetragonal and paraelectric cubic structures by decreasing the c/a ratio to a value close to unity. This study shows a way toward a strategy for modulating a crystal structure by using proper dopants for future applications in ferroelectricity-based devices.

Evidence for a percolative Mott insulator-metal transition in doped Sr2IrO4

Despite many efforts to rationalize the strongly correlated electronic ground states in doped Mott insulators, the nature of the doping induced insulator to metal transition is still a subject under intensive investigation. Here we probe the nanoscale electronic structure of the Mott insulator Sr$_2$IrO$_{4-\delta}$ with low-temperature scanning tunneling microscopy and find enhanced local density of states (LDOS) inside the Mott gap at the location of individual apical oxygen site defects. We visualize paths of enhanced conductance arising from the overlapping of defect states which induces finite LDOS at the Fermi level. By combining these findings with the typical spatial extension of isolated defects of about 2~nm, we show that the insulator to metal transition in Sr$_2$IrO$_{4-\delta}$ is of percolative nature.

An Electronic Correlation Approach to the Metal–Insulator Transition in the Half-Metallic Sr2FeMoO6Compound Doped With W

The ferromagnetic double perovskite Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FeMoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> (SFMO) system with half-metallicity and fairly high Curie temperature points to the possibility of designing spintronics materials operating at room temperature. On the other hand, the double perovskite Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FeWO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> is an antiferromagnetic insulator with the W(5d) states located at high energies and also with completely different magnetic and electronic properties than the ferromagnetic SFMO. The ferromagnetism and half-metallicity in SFMO have been explained within a strongly correlated picture, in which Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> (3d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> ) are localized spins in a high-spin S = 5/2 configuration and Mo <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5+</sup> (4d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> ) cores have one itinerant electron per formula unit (f.u.), which can hop to Fe sites only with an orientation antiparallel to that of the localized spin, thus stabilizing a ferromagnetic arrangement of local spins and fully opposite spin-polarized itinerant electrons. In this work, we study the effect of cationic doping on the behavior of \textT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> in SFMO with the Mo ions replaced by W ions, which leads to a metal-insulator transition. We use Green's function technique and the renormalization perturbation expansion method, in which the localized Fe spins and conduction Mo electrons interact via a double-exchange-type mechanism and the Hubbard model. Electronic correlations among the conduction electrons are included within a dynamical mean-field approach. Our results show a metal-insulator transition for W doping around x=0.2 in good agreement with experiments.

Size, disorder, and charge doping effects in the antiferromagnetic series Eu1-xAxGa4 (A = Ca, Sr, or La)

EuGa4 hosts a magnetic Eu2+ sublattice surrounded by a network of covalently-bound Ga atoms with the BaAl4 structure type (space group I4/mmm). In this study, we present the synthesis and characterization of three new single crystal substitutional series EuAx1−xGa4 with A ​= ​Ca, Sr, or La. X-ray diffraction and resistivity measurements show that Ca substitution induced a structural phase transition from the tetragonal crystal structure at high temperatures to the monoclinic crystal structure (CaGa4 type, space group C2/m) at low temperatures and suppressed the antiferromagnetic ordering temperature to 8.8 ​K for x ​= ​0.45. Comparatively, La or Sr substitution maintained the tetragonal crystal structure and suppressed the antiferromagnetic ordering temperatures to 6.7 ​K and 1.6 ​K for (A, x) = (La, 0.37) and (Sr, 0.91), respectively. In addition to suppressing the magnetic order, magnetization and specific heat measurements indicate the onset of anisotropic metamagnetic transitions in (La, 0.18), (La, 0.37), and (Sr, 0.63), along with an incommensurate-to-commensurate magnetic transition in (Sr, 0.38). By comparing these effects of doping EuGa4, we show how size, disorder, and charge determine the structure-physical property relations in EuGa4.

Optical Signature of a Crossover from Mott- to Slater-Type Gap in Sr2Ir1−xRhxO4

With optical spectroscopy we provide evidence that the insulator-metal transition in Sr_{2}Ir_{1-x}Rh_{x}O_{4} occurs close to a crossover from the Mott- to the Slater-type. The Mott gap at x=0 persists to high temperature and evolves without an anomaly across the Néel temperature, T_{N}. Upon Rh doping, it collapses rather rapidly and vanishes around x=0.055. Notably, just as the Mott gap vanishes yet another gap appears that is of the Slater-type and develops right below T_{N}. This Slater gap is only partial and is accompanied by a reduced scattering rate of the remaining free carriers, similar as in the parent compounds of the iron arsenide superconductors.

Influence of magnetism on Dirac semimetallic behavior in nonstoichiometric Sr1−yMn1−zSb2(y∼0.07,z∼0.02)

Nonstoichiometric Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ (y, z~$<$0.1) is known to exhibit a coexistence of magnetic order and the nontrivial semimetallic behavior related to Dirac or Weyl fermions. Here, we report inelastic neutron scattering analyses of the spin dynamics and density functional theory studies on the electronic properties of Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$. We observe a relatively large spin excitation gap $\approx$ 8.5 meV at 5 K, and the interlayer magnetic exchange constant only 2.8 \% of the dominant intralayer magnetic interaction, providing evidence that Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ exhibits a quasi-2D magnetism. Using density functional theory, we find a strong influence of magnetic orders on the electronic band structure and the Dirac dispersions near the Fermi level along the Y-S direction in the presence of a ferromagnetic ordering. Our study unveils novel interplay between the magnetic order, magnetic transition, and electronic property in Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$, and opens new pathways to control the relativistic band structure through magnetism in ternary compounds.

Molecular lattice clock with long vibrational coherence

Atomic lattice clocks have spurred numerous ideas for tests of fundamental physics, detection of general relativistic effects, and studies of interacting many-body systems. On the other hand, molecular structure and dynamics offer rich energy scales that are at the heart of new protocols in precision measurement and quantum information science. Here we demonstrate a fundamentally distinct type of lattice clock that is based on vibrations in diatomic molecules, and present coherent Rabi oscillations between weakly and deeply bound molecules that persist for 10's of milliseconds. This control is made possible by a state-insensitive magic lattice trap that weakly couples to molecular vibronic resonances and enhances the coherence time between molecules and light by several orders of magnitude. The achieved quality factor $Q=8\times10^{11}$ results from 30-Hz narrow resonances for a 25-THz clock transition in Sr$_2$. Our technique of extended coherent manipulation is applicable to long-term storage of quantum information in qubits based on ultracold polar molecules, while the vibrational clock enables precise probes of interatomic forces, tests of Newtonian gravitation at ultrashort range, and model-independent searches for electron-to-proton mass ratio variations.

Room temperature crystal structure and high temperature structural and magnetic phase transitions in Sr(Fe0.5Nb0.5)O3 ceramic

The room temperature structure of the perovskite Sr(Fe0.5Nb0.5)O3 ceramic has been investigated by Rietveld structure refinement using high resolution X-ray diffraction (XRD) data. The correct structure is determined to be tetragonal in the space group I4/mcm ruling out orthorhombic (Pbnm), tetragonal (P4 mm), and monoclinic structures previously reported by authors. The high temperature structural phase transition has been studied by Rietveld analysis using the high resolution XRD data in the temperature range of 300–850 K. A high temperature structural phase transition is observed from tetragonal (I4/mcm) to cubic (Pm3̅m) phase around ∼630 K. This phase transition was also confirmed by the heat flow experiment using differential scanning calorimetry. To confirm the nature of phase transition, we have studied the variation of integrated intensity (ISL) of superlattice peak and the oxygen octahedral tilt angle (φ) in a tetragonal structure with temperature. The temperature variations of these two parameters provide evidence for the tricritical nature of the phase transition. A magnetic phase transition is discovered in temperature dependence of magnetization M(T) around ∼708 K, which coincides with the dielectric anomaly temperature in loss tangent.

Dual-Mode Operation of an Optical Lattice Clock Using Strontium and Ytterbium Atoms.

We have developed an optical lattice clock that can operate in dual modes: a strontium (Sr) clock mode and an ytterbium (Yb) clock mode. Dual-mode operation of the Sr-Yb optical lattice clock is achieved by alternately cooling and trapping 87Sr and 171Yb atoms inside the vacuum chamber of the clock. Optical lattices for Sr and Yb atoms were arranged with horizontal and vertical configurations, respectively, resulting in a small distance of the order of between the trapped Sr and Yb atoms. The 1S0-3P0 clock transitions in the trapped atoms were interrogated in turn and the clock lasers were stabilized to the transitions. We demonstrated the frequency ratio measurement of the Sr and Yb clock transitions by using the dual-mode operation of the Sr-Yb optical lattice clock. The dual-mode operation can reduce the uncertainty of the blackbody radiation shift in the frequency ratio measurement, because both Sr and Yb atoms share the same blackbody radiation.

Imaging Optical Frequencies with 100 μHz Precision and 1.1 μm Resolution.

We implement imaging spectroscopy of the optical clock transition of lattice-trapped degenerate fermionic Sr in the Mott-insulating regime, combining micron spatial resolution with submillihertz spectral precision. We use these tools to demonstrate atomic coherence for up to 15s on the clock transition and reach a record frequency precision of 2.5×10^{-19}. We perform the most rapid evaluation of trapping light shifts and record a 150mHz linewidth, the narrowest Rabi line shape observed on a coherent optical transition. The important emerging capability of combining high-resolution imaging and spectroscopy will improve the clock precision, and provide a path towards measuring many-body interactions and testing fundamental physics.

Structural phase transition and electrical properties of Sr2+ substituted porous PMN‐PZT ceramics

AbstractIn this study, Sr2+ modified porous PMN‐PZT ceramics with one‐dimensional pore channels were produced by the ionotropic gelation process of alginate/PMN‐PZT suspensions. The ion‐exchange method was employed during the fabrication procedure to adjust the content of SrO addition. With the SrO addition increasing from 1.653 wt.% to 2.957 wt.%, the structural phase of porous PMN‐PZT ceramics transformed from rhombohedral (R) to tetragonal (T) perovskite phase. Accordingly, the electromechanical coupling coefficient (kt) value of porous PMN‐PZT ceramics decreased from 64.7% to 58.7%, while the hydrostatic figure of merit (HFOM) value increased from 1510 to 5547 × 10−15 m2/N, and acoustic impedance Z value ranged from 4.59 to 7.55 MRayls, which helped for applications in underwater transducers or hydrophones.

Nature of the antiferromagnetic and nematic transitions in Sr1−xBaxFe1.97Ni0.03As2

We have systematically studied the antiferromagnetic and nematic transitions in Sr$_{1-x}$Ba$_x$Fe$_{1.97}$Ni$_{0.03}$As$_2$ by magnetic susceptibility and uniaxial-pressure resistivity measurements, respectively. The derivatives of the temperature dependence of both magnetic and nematic susceptibilities show clearly sharp peak when the transitions are first-order. Accordingly, we show that while both of the magnetic and nematic transitions change from first-order to second-order with increasing Barium doping level, there is a narrow doping range where the former becomes second-order but the latter remains first-order, which has never been realized before in other systems. Moreover, the antiferromagnetic and nematic transition temperatures become different and the jump of nematic susceptibility becomes small in this intermediate doping range. Our results provide key information on the interplay between magnetic and nematic transitions. Concerning the current debate on the microscopic models for nematicity in iron-based superconductors, these observations agree with the magnetic scenario for an itinerant fermionic model in excellent details.

All-diode-laser cooling of Sr+ isotope ions for analytical applications

Trapping and cooling of Sr+ isotope ions by an all-diode-laser system has been demonstrated in order to develop a novel mass spectrometric technique in combination with ion trap-laser cooling. First, we constructed external cavity diode lasers and associated stabilization apparatus for laser cooling of Sr+ ions. The transition frequencies confirmed by optogalvanic spectroscopy enabled successful cooling of 88Sr+ ions. An image of two trapped ions has been captured by CCD camera. Minor isotopes, 84Sr+ and 86Sr+, were also cooled and trapped. From an analysis of the observed spectra of a string crystal of each isotope, the isotope shifts of the cooling transition (5s 2S1/2 → 5p 2P1/2) of Sr+ ions were determined to be +371(8) MHz for Δν84–88 and +169(8) MHz for Δν86–88. In the case of the repumping transition (4d 2D3/2 → 5p 2P1/2), Δν84–88 and Δν86–88 were measured to be −833(6) and −400(5) MHz, respectively. These values are in good agreement with previously reported values.