Kuroda, Kenta*; Arai, Yosuke*; Rezaei, N.*; Kunisada, So*; Sakuragi, Shunsuke*; Alaei, M.*; Kinoshita, Yuto*; Bareille, C.*; Noguchi, Ryo*; Nakayama, Mitsuhiro*; et al.
Nature Communications (Internet), 11, p.2888_1 - 2888_9, 2020/06
Takahashi, Ryo*; Chudo, Hiroyuki; Matsuo, Mamoru; Harii, Kazuya*; Onuma, Yuichi*; Maekawa, Sadamichi; Saito, Eiji
Nature Communications (Internet), 11, p.3009_1 - 3009_6, 2020/06
Al-Shayeb, B.*; Sachzdeva, R.*; Chen, L.-X.*; Ward, F.*; Munk, P.*; Devoto, A.*; Castelle, C. J.*; Olm, M. R.*; Bouma-Gregson, K.*; Amano, Yuki; et al.
Nature, 578(7795), p.425 - 431, 2020/02
Li, X.*; Liu, P.-F.*; Zhao, E.*; Zhang, Z.*; Guide, T.*; Le, M. D.*; Avdeev, M.*; Ikeda, Kazutaka*; Otomo, Toshiya*; Kofu, Maiko; et al.
Nature Communications (Internet), 11(1), p.942_1 - 942_9, 2020/02
In high-performance thermoelectric materials, there are two main low thermal conductivity mechanisms: the phonon anharmonic and phonon scattering resulting from the dynamic disorder, which have been successfully revealed by inelastic neutron scattering. Using neutron scattering and ab initio calculations, we report here a mechanism of static local structure distortion combined with phonon-anharmonic-induced ultralow lattice thermal conductivity in -MgAgSb. Since the transverse acoustic phonons are almost fully scattered by the intrinsic distorted rocksalt sublattice in this compound, the heat is mainly transported by the longitudinal acoustic phonons. The ultralow thermal conductivity in -MgAgSb is attributed to its atomic dynamics being altered by the structure distortion, which presents a possible microscopic route to enhance the performance of similar thermoelectric materials.
Komatsu, Kazuki*; Machida, Shinichi*; Noritake, Fumiya*; Hattori, Takanori; Sano, Asami; Yamane, Ryo*; Yamashita, Keishiro*; Kagi, Hiroyuki*
Nature Communications (Internet), 11(1), p.464_1 - 464_5, 2020/02
Water freezes below 0C at ambient pressure ordinarily to ice I, with hexagonal stacking sequence. Under certain conditions, ice with a cubic stacking sequence can also be formed, but ideal ice I without stacking-disorder has never been formed until recently. Here we demonstrate a route to obtain ice I without stacking-disorder by degassing hydrogen from the high-pressure form of hydrogen hydrate, C, which has a host framework isostructural with ice I. The stacking-disorder free ice I is formed from C via an intermediate amorphous or nano-crystalline form under decompression, unlike the direct transformations occurring in ice XVI from neon hydrate, or ice XVII from hydrogen hydrate. The obtained ice I shows remarkable thermal stability, until the phase transition to ice I at 250 K, originating from the lack of dislocations. This discovery of ideal ice I will promote understanding of the role of stacking-disorder on the physical properties of ice as a counter end-member of ice I.
Martin, P. G.*; Louvel, M.*; Cipiccia, S.*; Jones, C. P.*; Batey, D. J.*; Hallam, K. R.*; Yang, I. A. X.*; Satou, Yukihiko; Rau, C.*; Mosselmans, J. F. W.*; et al.
Nature Communications (Internet), 10(1), p.2801_1 - 2801_7, 2019/06
Synchrotron radiation (SR) analysis techniques alongside secondary ion mass spectrometry (SIMS) measurements have been made on sub-mm particulate material derived from reactor Unit 1 of the Fukushima Daiichi Nuclear Power Plant (FDNPP). Using these methods, it has been possible to investigate the distribution, state and isotopic composition of micron-scale U particulate contained within the larger Si-based ejecta material. Through combined SR micro-focused X-ray fluorescence (SR-micro-XRF) and absorption contrast SR micro-focused X-ray tomography (SR-micro-XRT), the U particulate was found to be located around the exterior circumference of the highly-porous particle. Synchrotron radiation micro-focused X-ray absorption near edge structure (SR-micro-XANES) analysis of a number of these entrapped particles revealed them to exist within the U(IV) oxidation state, as UO, and identical in structure to reactor fuel. Confirmation that this U was of nuclear origin (U-enriched) was provided through secondary ion mass spectrometry (SIMS) analysis with an isotopic enrichment ratio characteristic of a provenance from reactor Unit 1 at the FDNPP. These results provide clear evidence of the event scenario (that a degree of core fragmentation and release occurred from reactor Unit 1), with such spent fuel ejecta existing; (i) within the stable U(IV) oxidation state; and (ii) contained within a bulk Si-based particle. While this U is unlikely to represent an environmental or health hazard, such assertions would likely change, however, should break-up of the Si-containing bulk particle occur. However, more important to the long-term decommissioning of the reactors (and clean-up) on the FDNPP, is the knowledge that core integrity of reactor Unit 1 was compromised with nuclear material existing outside of the reactors primary containment.
Harii, Kazuya; Seo, Y.-J.*; Tsutsumi, Yasumasa*; Chudo, Hiroyuki; Oyanagi, Koichi*; Matsuo, Mamoru; Shiomi, Yuki*; Ono, Takahito*; Maekawa, Sadamichi; Saito, Eiji
Nature Communications (Internet), 10(1), p.2616_1 - 2616_5, 2019/06
Wang, J.*; Ran, K.*; Li, S.*; Ma, Z.*; Bao, S.*; Cai, Z.*; Zhang, Y.*; Nakajima, Kenji; Kawamura, Seiko; ermk, P.*; et al.
Nature Communications (Internet), 10, p.2802_1 - 2802_6, 2019/06
Nawa, Kazuhiro*; Tanaka, Kimihito*; Kurita, Nubuyuki*; Sato, Taku*; Sugiyama, Haruki*; Uekusa, Hidehiro*; Kawamura, Seiko; Nakajima, Kenji; Tanaka, Hidekazu*
Nature Communications (Internet), 10, p.2096_1 - 2096_8, 2019/05
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 BaCuSiOCl. 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 BaCuSiOCl 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.
Li, B.*; Kawakita, Yukinobu; Kawamura, Seiko; Sugahara, Takeshi*; Wang, H.*; Wang, J.*; Chen, Y.*; Kawaguchi, Saori*; Kawaguchi, Shogo*; Ohara, Koji*; et al.
Nature, 567(7749), p.506 - 510, 2019/03
Refrigeration is of vital importance for modern society for example, for food storage and air conditioning- and 25 to 30% of the world's electricity is consumed for refrigeration. 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 potential. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades. 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.
Aidala, C.*; Hasegawa, Shoichi; Imai, Kenichi; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 312 of others*
Nature Physics, 15(3), p.214 - 220, 2019/03
Gttler, M.*; Generalov, A.*; Fujimori, Shinichi; Kummer, K.*; Chikina, A.*; Seiro, S.*; Danzenbcher, S.*; Koroteev, Yu. M.*; Chulkov, E. V.*; Radovic, M.*; et al.
Nature Communications (Internet), 10(1), p.796_1 - 796_7, 2019/02
Matheus Carnevali, P. B.*; Schulz, F.*; Castelle, C. J.*; Kantor, R. S.*; Shih, P. M.*; Sharon, I.*; Santini, J.*; Olm, M. R.*; Amano, Yuki; Thomas, B. C.*; et al.
Nature Communications (Internet), 10, p.463_1 - 463_15, 2019/01
Marsh, B. A.*; Day Goodacre, T.*; Tsunoda, Yusuke*; Andreyev, A. N.; 41 of others*
Nature Physics, 14(12), p.1163 - 1167, 2018/12
Lustikova, J.*; Shiomi, Yuki*; Yokoi, Naoto*; Kabeya, Noriyuki*; Kimura, Noriaki*; Ienaga, Koichiro*; Kaneko, Shinichi*; Okuma, Satoshi*; Takahashi, Saburo*; Saito, Eiji
Nature Communications (Internet), 9, p.4922_1 - 4922_6, 2018/11
Terada, Noriki*; Qureshi, N.*; Chapon, L. C.*; Osakabe, Toyotaka
Nature Communications (Internet), 9, p.4368_1 - 4368_9, 2018/10
Uchida, Kenichi*; Daimon, Shunsuke*; Iguchi, Ryo*; Saito, Eiji
Nature, 558(7708), p.95 - 99, 2018/06
Qiu, Z.*; Hou, D.*; Barker, J.*; Yamamoto, Kei; Gomonay, O.*; Saito, Eiji*
Nature Materials, 17(7), p.577 - 580, 2018/05
Colossal magnetoresistance (CMR) refers to a large change in electrical conductivity induced by a magnetic field in the vicinity of a metal-insulator transition. CMR occurs due to a correlation between the magnetic structure and electron conduction and has inspired extensive studies for decades. Here, in the antiferromagnetic insulator CrO, we found a sharp transition between conducting and nonconducting states for spin currents at room temperature. The spin-current transmission changes by two orders of magnitude within a narrow temperature window of 14K around the Neel temperature. The spin conductor-nonconductor transition can be modulated by a magnetic field, giving an isothermal change of spin-current transmission of up to 500%, effectively an on-off switch for spin currents.
Nordlund, K.*; Zinkle, S. J.*; Sand, A. E.*; Granberg, F.*; Averback, R. S.*; Stoller, R.*; Suzudo, Tomoaki; Malerba, L.*; Banhart, F.*; Weber, W. J.*; et al.
Nature Communications (Internet), 9, p.1084_1 - 1084_8, 2018/03
Atomic collision processes are fundamental to numerous advanced materials technologies such as electron microscopy, semiconductor processing and nuclear power generation. Experimental and computer simulation studies over the past several decades provide the physical basis for understanding the atomic-scale processes occurring during primary displacement events. The current international standard for quantifying this particle damage, the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model, has nowadays several well-known limitations. In particular, the number of radiation defects produced in energetic cascades in metals is only 1/3 the NRT-dpa prediction, while the number of atoms involved in atomic mixing is about a factor of 30 larger than the dpa value. Here we propose two new complementary displacement production estimators.
Li, B.; Wang, H.*; Kawakita, Yukinobu; Zhang, Q.*; Feygenson, M.*; Yu, H. L.*; Wu, D.*; Ohara, Koji*; Kikuchi, Tatsuya*; Shibata, Kaoru; et al.
Nature Materials, 17(3), p.226 - 230, 2018/03