The crystal structure and bonding environment of K2Ca(CO3)2bütschliite were probed under isothermal compression via Raman spectroscopy to 95 GPa and single crystal and powder X-ray diffraction to 12 and 68 GPa, respectively. A second order Birch-Murnaghan equation of state fit to the X-ray data yields a bulk modulus,
We consider a model of electrons at zero temperature, with a repulsive interaction which is a function of the energy transfer. Such an interaction can arise from the combination of electron–electron repulsion at high energies and the weaker electron–phonon attraction at low energies. As shown in previous works, superconductivity can develop despite the overall repulsion due to the energy dependence of the interaction, but the gap Δ(
- Award ID(s):
- 1834856
- PAR ID:
- 10381686
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- npj Quantum Materials
- Volume:
- 7
- Issue:
- 1
- ISSN:
- 2397-4648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract GPa with an imposed value of$${K}_{0}=46.9$$ for the ambient pressure phase. Compression of bütschliite is highly anisotropic, with contraction along the$${K}_{0}^{\prime}= 4$$ c -axis accounting for most of the volume change. Bütschliite undergoes a phase transition to a monoclinicC 2/m structure at around 6 GPa, mirroring polymorphism within isostructural borates. A fit to the compression data of the monoclinic phase yields Å3$${V}_{0}=322.2$$ $$,$$ GPa and$${K}_{0}=24.8$$ using a third order fit; the ability to access different compression mechanisms gives rise to a more compressible material than the low-pressure phase. In particular, compression of the$${K}_{0}^{\prime}=4.0$$ C 2/m phase involves interlayer displacement and twisting of the [CO3] units, and an increase in coordination number of the K+ion. Three more phase transitions, at ~ 28, 34, and 37 GPa occur based on the Raman spectra and powder diffraction data: these give rise to new [CO3] bonding environments within the structure. -
Abstract The electric
E 1 and magneticM 1 dipole responses of the nucleus$$N=Z$$ Mg were investigated in an inelastic photon scattering experiment. The 13.0 MeV electrons, which were used to produce the unpolarised bremsstrahlung in the entrance channel of the$$^{24}$$ Mg($$^{24}$$ ) reaction, were delivered by the ELBE accelerator of the Helmholtz-Zentrum Dresden-Rossendorf. The collimated bremsstrahlung photons excited one$$\gamma ,\gamma ^{\prime }$$ , four$$J^{\pi }=1^-$$ , and six$$J^{\pi }=1^+$$ states in$$J^{\pi }=2^+$$ Mg. De-excitation$$^{24}$$ rays were detected using the four high-purity germanium detectors of the$$\gamma $$ ELBE setup, which is dedicated to nuclear resonance fluorescence experiments. In the energy region up to 13.0 MeV a total$$\gamma $$ is observed, but this$$B(M1)\uparrow = 2.7(3)~\mu _N^2$$ nucleus exhibits only marginal$$N=Z$$ E 1 strength of less than e$$\sum B(E1)\uparrow \le 0.61 \times 10^{-3}$$ fm$$^2 \, $$ . The$$^2$$ branching ratios in combination with the expected results from the Alaga rules demonstrate that$$B(\varPi 1, 1^{\pi }_i \rightarrow 2^+_1)/B(\varPi 1, 1^{\pi }_i \rightarrow 0^+_{gs})$$ K is a good approximative quantum number for Mg. The use of the known$$^{24}$$ strength and the measured$$\rho ^2(E0, 0^+_2 \rightarrow 0^+_{gs})$$ branching ratio of the 10.712 MeV$$B(M1, 1^+ \rightarrow 0^+_2)/B(M1, 1^+ \rightarrow 0^+_{gs})$$ level allows, in a two-state mixing model, an extraction of the difference$$1^+$$ between the prolate ground-state structure and shape-coexisting superdeformed structure built upon the 6432-keV$$\varDelta \beta _2^2$$ level.$$0^+_2$$ -
Abstract We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive
meson muoproduction at COMPASS using 160 GeV/$$\rho ^0$$ c polarised and$$ \mu ^{+}$$ beams impinging on a liquid hydrogen target. The measurement covers the kinematic range 5.0 GeV/$$ \mu ^{-}$$ $$c^2$$ 17.0 GeV/$$< W<$$ , 1.0 (GeV/$$c^2$$ c )$$^2$$ 10.0 (GeV/$$< Q^2<$$ c ) and 0.01 (GeV/$$^2$$ c )$$^2$$ 0.5 (GeV/$$< p_{\textrm{T}}^2<$$ c ) . Here,$$^2$$ W denotes the mass of the final hadronic system, the virtuality of the exchanged photon, and$$Q^2$$ the transverse momentum of the$$p_{\textrm{T}}$$ meson with respect to the virtual-photon direction. The measured non-zero SDMEs for the transitions of transversely polarised virtual photons to longitudinally polarised vector mesons ($$\rho ^0$$ ) indicate a violation of$$\gamma ^*_T \rightarrow V^{ }_L$$ s -channel helicity conservation. Additionally, we observe a dominant contribution of natural-parity-exchange transitions and a very small contribution of unnatural-parity-exchange transitions, which is compatible with zero within experimental uncertainties. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow one to evaluate in a model-dependent way the role of parton helicity-flip GPDs in exclusive production.$$\rho ^0$$ -
A bstract We report the first measurement of the inclusive
e +e − → $$ b\overline{b} $$ → $$ {D}_s^{\pm } $$ X ande +e − → $$ b\overline{b} $$ → D 0/ $$ {\overline{D}}^0 $$ X cross sections in the energy range from 10. 63 to 11. 02 GeV. Based on these results, we determineσ (e +e − → $$ {B}_s^0{\overline{B}}_s^0 $$ X ) andσ (e +e − → $$ B\overline{B} $$ X ) in the same energy range. We measure the fraction of events at Υ(10860) to be$$ {B}_s^0 $$ f s= ( )%. We determine also the ratio of the$$ {22.0}_{-2.1}^{+2.0} $$ inclusive branching fractions$$ {B}_s^0 $$ ($$ \mathcal{B} $$ $$ {B}_s^0 $$ → D 0/ $$ {\overline{D}}^0 $$ X )/ ($$ \mathcal{B} $$ $$ {B}_s^0 $$ → $$ {D}_s^{\pm } $$ X ) = 0. 416 ± 0. 018 ± 0. 092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energye +e − collider. -
Abstract Let
be an elliptically fibered$$X\rightarrow {{\mathbb {P}}}^1$$ K 3 surface, admitting a sequence of Ricci-flat metrics collapsing the fibers. Let$$\omega _{i}$$ V be a holomorphicSU (n ) bundle overX , stable with respect to . Given the corresponding sequence$$\omega _i$$ of Hermitian–Yang–Mills connections on$$\Xi _i$$ V , we prove that, ifE is a generic fiber, the restricted sequence converges to a flat connection$$\Xi _i|_{E}$$ . Furthermore, if the restriction$$A_0$$ is of the form$$V|_E$$ for$$\oplus _{j=1}^n{\mathcal {O}}_E(q_j-0)$$ n distinct points , then these points uniquely determine$$q_j\in E$$ .$$A_0$$