Branching Ratio Study of Resonant X-Ray Scattering Intensities of GdB4

Resonant X-ray scattering measurements for a GdB4 single crystal have been carried out at Gd L-3- and L-2-edges. Branching ratios between x-ray scattering intensities at two x-ray energies are different for resonance peaks. Their analysis shows different anisotropic characters of 5d electron states of Gd ions corresponding to the peaks.11sciescopuskc

Q Dependence of Magnetic Resonance Mode on FeTe0.5Se0.5 Studied by Inelastic Neutron Scattering

Inelastic neutron scattering measurements have been performed on a superconducting single crystal FeTe 0.5 Se 0.5 to examine the Q -dependent enhancement of the dynamical structure factor, S ( Q , E ) , from Q = (0, 0) to ( π , π ), including ( π , 0) in the superconducting state. In most of iron-based superconductors, S ( Q , E ) is enhanced at Q = ( π , 0), where the “magnetic resonance mode” is commonly observed in the unfolded Brillouin zone. Constant-E cuts of S ( Q , E ) suggest that the enhancement is not uniform in the magnetic excitation, and limited around Q = ( π , 0). This result is consistent with the theoretical simulation of the magnetic resonance mode due to the Bardeen–Cooper–Schrieffer coherence factor with the sign-reversing order parameter of s ± wave

Frustration driven C-4 symmetric orders in a naturally heterostructured superconductor Sr2VO3FeAs

A subtle balance between competing interactions in iron-based superconductors (FeSCs) can be tipped by additional interfacial interactions in a heterostructure, often inducing exotic phases with unprecedented properties. Particularly when the proximity-coupled layer is magnetically active, rich phase diagrams are expected in FeSCs, but this has not been explored yet. Here, using high-accuracy 75As and 51V nuclear magnetic resonance measurements, we investigate an electronic phase that emerges in the FeAs layer below T0 ~ 155 K of Sr2VO3FeAs, a naturally assembled heterostructure of an FeSC and a Mottinsulating vanadium oxide. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order in the FeAs layers, without either static magnetism or broken C4 symmetry, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling stabilizes a hidden order in FeSCs, which may also apply to other strongly correlated heterostructures. © The Author(s) 20171111sciescopu

Weak-coupling to strong-coupling quantum criticality crossover in a Kitaev quantum spin liquid alpha-RuCl3

We report a quantum criticality crossover representing two different universal scaling behaviors in a Kitaev quantum magnetic material alpha-RuCl3. alpha-RuCl3 presents both a symmetry-breaking antiferromagnetic order and a long-range entangled topological order of a quantum spin liquid, and thus could be a candidate system for a unique universality class involving deconfined fractionalized excitations of the local Z(2) fluxes and itinerant Majorana fermions. Theoretical analyses on the inelastic neutron scattering, ac-magnetic susceptibility, and specific heat results demonstrate that Wilson-Fisher-Yukawa-type 'conventional' weak-coupling quantum criticality in high-energy scales crosses over to heavy-fermion-type 'local' strong-coupling one in low-energy scales. Our findings provide deep insight on how quantum criticality evolves in fermion-boson coupled topological systems with different types of deconfined fermions.11Nsciescopu

Frustration-driven C-4 symmetric order in a naturally-heterostructured superconductor Sr2VO3FeAs

A subtle balance between competing interactions in iron-based superconductors (FeSCs) can be tipped by additional interfacial interactions in a heterostructure, often inducing exotic phases with unprecedented properties. Particularly when the proximity-coupled layer is magnetically active, rich phase diagrams are expected in FeSCs, but this has not been explored yet. Here, using high-accuracy 75As and 51V nuclear magnetic resonance measurements, we investigate an electronic phase that emerges in the FeAs layer below T0 ~ 155 K of Sr2VO3FeAs, a naturally assembled heterostructure of an FeSC and a Mottinsulating vanadium oxide. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order in the FeAs layers, without either static magnetism or broken C4 symmetry, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling stabilizes a hidden order in FeSCs, which may also apply to other strongly correlated heterostructures.112Nsciescopu

High-Voltage-Driven Surface Structuring and Electrochemical Stabilization of Ni-Rich Layered Cathode Materials for Li Rechargeable Batteries

Layered lithium-nickel-cobalt-manganese oxide (NCM) materials have emerged as promising alternative cathode materials owing to their high energy density and electrochemical stability. Although high reversible capacity has been achieved for Ni-rich NCM materials when charged beyond 4.2 V versus Li+/Li, full lithium utilization is hindered by the pronounced structural degradation and electrolyte decomposition. Herein, the unexpected realization of sustained working voltage as well as improved electrochemical performance upon electrochemical cycling at a high operating voltage of 4.9 V in the Ni-rich NCM LiNi0.895Co0.085Mn0.02O2 is presented. The improved electrochemical performance at a high working voltage at 4.9 V is attributed to the removal of the resistive Ni2+O rock-salt surface layer, which stabilizes the voltage profile and improves retention of the energy density during electrochemical cycling. The manifestation of the layered Ni2+O rock-salt phase along with the structural evolution related to the metal dissolution are probed using in situ X-ray diffraction, neutron diffraction, transmission electron microscopy, and X-ray absorption spectroscopy. The findings help unravel the structural complexities associated with high working voltages and offer insight for the design of advanced battery materials, enabling the realization of fully reversible lithium extraction in Ni-rich NCM materials