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We investigated neutron flux at a sample position and energy resolution of a direct-geometry disk-chopper spectrometer AMATERAS under various chopper conditions and compared them with simulations and calculations. The measured flux was comparable to that of similar high-flux spectrometers. The resolution when using a pulse-shaping chopper correlated well with the analytical calculations, including the thickness of the disk chopper, the sample size, and the penetration depth into the detector. The results show that the chopper, placed at the intermediate distance of the primary spectrometer, functions as a pulse shaper that optimizes the flux and resolution below the incident energy of 10 meV. [ABSTRACT FROM AUTHOR]

The basis for our understanding of quantum magnetism has been the study of elegantly simple model systems. However, even for the antiferromagnetic honeycomb lattice with isotropic spin interactions–one of the simplest model systems–a detailed understanding of quantum effects is still lacking. Here, using inelastic neutron scattering measurements of the honeycomb lattice material YbCl3, we elucidate how quantum effects renormalize the single-magnon and multimagnon excitations and how this renormalization can be tuned and ultimately driven to the classical limit by applying a magnetic field. Additionally, our work reveals that the quantum effects tuned by the magnetic field not only renormalize the magnetic excitations but also induce a distinctive sharp feature inside the multimagnon continuum. From a more general perspective, this result demonstrates that structures within magnetic continua can occur over a wide experimental parameter space and can be used as a reliable means of identifying quantum phenomena. The honeycomb lattice is of fundamental importance for understanding quantum spin liquids and frustrated magnetism more generally. Here, the authors use inelastic neutron scattering to investigate the honeycomb antiferromagnet YbCl3 showing how quantum effects renormalize the single-magnon and multimagnon excitations, shedding further light on the mechanisms of quantum magnetism in honeycomb-lattice compounds. [ABSTRACT FROM AUTHOR]

Glassy magnetic behavior has been observed in a wide range of crystalline magnetic materials called spin glass. Here, we report spin glass behavior in a structural glass of a magnetic ionic liquid, C4mimFeCl4. Magnetization measurements demonstrate that an antiferromagnetic ordering occurs at TN = 2.3 K in the crystalline state, while a spin glass transition occurs at TSG = 0.4 K in the structural glass state. In addition, localized magnetic excitations were found in the spin glass state by inelastic neutron scattering, in contrast to spin-wave excitations in the ordered phase of the crystalline sample. The localized excitation was scaled by the Bose population factor below TSG and gradually disappeared above TSG. This feature is highly reminiscent of boson peaks commonly observed in structural glasses. We suggest the "magnetic" boson peak to be one of the inherent dynamics of a spin glass state. [ABSTRACT FROM AUTHOR]

Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu6AlBiO4(SO4)5Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (μSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state. There exist many theoretical models of frustrated quantum magnetism, most of which lack convincing experimental realisations. Here the authors combine several experimental methods to argue that KCu6AlBiO4(SO4)5Cl behaves as a square-kagome-lattice quantum Heisenberg antiferromagnet. [ABSTRACT FROM AUTHOR]

We investigated the low-energy incommensurate (IC) magnetic fluctuations in Sr2RuO4 by the high-resolution inelastic neutron scattering measurements and random phase approximation (RPA) calculations. We observed a spin resonance with energy of ħωres = 0.56 meV centered at a characteristic wavevector \(\mathbf{Q}_{\text{res}} = (0.3,0.3,0.5)\). The resonance energy corresponds well to the superconducting gap 2Δ = 0.56 meV estimated by the tunneling spectroscopy. The spin resonance shows the L modulation with a maximum at around L = 0.5. The L modulated intensity of the spin resonance and our RPA calculations indicate that the superconducting gaps regarding the quasi-one-dimensional α and β sheets at the Fermi surfaces have the horizontal line nodes. These results may set a strong constraint on the pairing symmetry of Sr2RuO4. We also discuss the implications on possible superconducting order parameters. [ABSTRACT FROM AUTHOR]

The workshop is hosted by the neutron and synchrotron facilities that belong to ISSE in turn, and the 11 SP th sp edition was the first time to be held in an Asian country. The 11 SP th sp International Workshop on Sample Environment at Scattering Facilities was successfully held at Resort Hotel Laforet Nasu, Tochigi, Japan, from August 28 to September 1. [Extracted from the article]

Refrigeration is of vital importance for modern society—for example, for food storage and air conditioning—and 25 to 30 per cent of the world's electricity is consumed for refrigeration1. Current refrigeration technology mostly involves the conventional vapour compression cycle, but the materials used in this technology are of growing environmental concern because of their large global warming potential2. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades3–5. However, their application is restricted by the limited performance of current caloric materials, owing to small isothermal entropy changes and large driving magnetic fields. Here we report colossal barocaloric effects (CBCEs) (barocaloric effects are cooling effects of pressure-induced phase transitions) in a class of disordered solids called plastic crystals. The obtained entropy changes in a representative plastic crystal, neopentylglycol, are about 389 joules per kilogram per kelvin near room temperature. Pressure-dependent neutron scattering measurements reveal that CBCEs in plastic crystals can be attributed to the combination of extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of these materials. Our study establishes the microscopic mechanism of CBCEs in plastic crystals and paves the way to next-generation solid-state refrigeration technologies. Colossal barocaloric effects are observed in the plastic crystal neopentylglycol and found to originate from the extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of the material. [ABSTRACT FROM AUTHOR]

We present the status of the low-temperature devices shared by several neutron instruments of the Materials and Life Science Experimental Facility (MLF), J-PARC. In recent years, the Cryogenics and Magnets group of the Sample Environment (SE) team has introduced three cryostats at the MLF: a top-loading 4He cryostat, a bottom-loading 3He cryostat, and a 3He–4He dilution refrigerator insert. The group also manages a superconducting magnet which entered into service in 2012. Progress has been made with these SE, including the development of a new system for controlling the 3He cryostat and an oscillating radial collimator for using efficiently the superconducting magnet. These innovations have significantly increased the frequency with which these cryostats and magnet are used. During the last Japanese fiscal year, some of them were used approximately half of the total number of days of beam operation. [ABSTRACT FROM AUTHOR]

Superconductivity mediated by phonons is typically conventional, exhibiting a momentum-independent s-wave pairing function, due to the isotropic interactions between electrons and phonons along different crystalline directions. Here, by performing inelastic neutron scattering measurements on a superconducting single crystal of Sr0.1Bi2Se3, a prime candidate for realizing topological superconductivity by doping the topological insulator Bi2Se3, we find that there exist highly anisotropic phonons, with the linewidths of the acoustic phonons increasing substantially at long wavelengths, but only for those along the [001] direction. This observation indicates a large and singular electron-phonon coupling at small momenta, which we propose to give rise to the exotic p-wave nematic superconducting pairing in the MxBi2Se3 (M = Cu, Sr, Nb) superconductor family. Therefore, we show these superconductors to be example systems where electron-phonon interaction can induce more exotic superconducting pairing than the s-wave, consistent with the topological superconductivity. Superconductivity mediated by phonons is usually conventional due to isotropic electron-phonon coupling. Here, Wang et al. report highly anisotropic phonons only along [001] direction in Sr0.1Bi2Se3, indicating a singular electron-phonon coupling which favors a p-wave nematic superconductivity scenario. [ABSTRACT FROM AUTHOR]

Search for topological materials has been actively promoted in the field of condensed matter physics for their potential application in energy-efficient information transmission and processing. Recent studies have revealed that topologically invariant states, such as edge states in topological insulators, can emerge not only in a fermionic electron system but also in a bosonic system, enabling nondissipative propagation of quasiparticles. Here we report the topologically nontrivial triplon bands measured by inelastic neutron scattering on the spin-1/2 two-dimensional dimerized antiferromagnet Ba2CuSi2O6Cl2. The excitation spectrum exhibits two triplon bands that are clearly separated by a band gap due to a small alternation in interdimer exchange interaction, consistent with a refined crystal structure. By analytically modeling the triplon dispersion, we show that Ba2CuSi2O6Cl2 is the first bosonic realization of the coupled Su-Schrieffer-Heeger model, where the presence of topologically protected edge states is prompted by a bipartite nature of the lattice. Topological edge states can emerge not only in a fermionic electron system but also in a bosonic system. Here, Nawa et al. report topologically nontrivial triplon bands in a two-dimensional dimerized quantum antiferromagnet Ba2CuSi2O6Cl2, suggesting a bosonic realization of the coupled Su-Schrieffer-Heeger model. [ABSTRACT FROM AUTHOR]

Perovskite CH3NH3PbI3 exhibits outstanding photovoltaic performances, but the understanding of the atomic motions remains inadequate even though they take a fundamental role in transport properties. Here, we present a complete atomic dynamic picture consisting of molecular jumping rotational modes and phonons, which is established by carrying out high-resolution time-of-flight quasi-elastic and inelastic neutron scattering measurements in a wide energy window ranging from 0.0036 to 54 meV on a large single crystal sample, respectively. The ultrafast orientational disorder of molecular dipoles, activated at ∼165 K, acts as an additional scattering source for optical phonons as well as for charge carriers. It is revealed that acoustic phonons dominate the thermal transport, rather than optical phonons due to sub-picosecond lifetimes. These microscopic insights provide a solid standing point, on which perovskite solar cells can be understood more accurately and their performances are perhaps further optimized. [ABSTRACT FROM AUTHOR]