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Temporally decoherent and spatially coherent vibrations in metal halide perovskites

Zhang, D.*; Hu, X.*; Chen, T.*; Abernathy, D. L.*; 梶本 亮一; 中村 充孝; 古府 麻衣子; Foley, B. J.*; Yoon, M.*; Choi, J. J.*; et al.

Physical Review B, 102(22), p.224310_1 - 224310_10, 2020/12

The long carrier lifetime and defect tolerance in metal halide perovskites (MHPs) are major contributors to the superb performance of MHP optoelectronic devices. Large polarons were reported to be responsible for the long carrier lifetime. Yet microscopic mechanisms of the large polaron formation, including the so-called phonon melting, are still under debate. Here, time-of-flight inelastic neutron scattering experiments and first-principles density-functional theory calculations were employed to investigate the lattice vibrations (or phonon dynamics) in methylammonium lead iodide, a prototypical example of MHPs. Our findings are that optical phonons lose temporal coherence gradually with increasing temperature which vanishes at the orthorhombic-to-tetragonal structural phase transition. Surprisingly, however, we found that the spatial coherence is still retained throughout the decoherence process. We argue that the temporally decoherent and spatially coherent vibrations contribute to the formation of large polarons in this metal halide perovskite.


Nature of structural instabilities in superconducting Sr$$_3$$Ir$$_4$$Sn$$_{13}$$

金子 耕士; Cheung, Y. W.*; Hu, Y.*; 今井 正樹*; 谷奥 泰明*; 金川 響*; 村川 譲一*; 森山 広大*; Zhang, W.*; Lai, K. T.*; et al.

JPS Conference Proceedings (Internet), 30, p.011032_1 - 011032_6, 2020/03

A quantum critical point appears as a second-order phase transition which takes place at zero temperature. In contrast to heavy-fermion systems in which magnetism often plays a vital role, recent studies revealed that structural instabilities can drive a system to a quantum critical point as well. In quasi-skutterudite (Ca,Sr)$$_3T_4$$Sn$$_{13}$$ ($$T$$=Rh, Ir), Sr$$_3$$Ir$$_4$$Sn$$_{13}$$ exhibits superconductivity around $$T_{rm sc}$$$${sim}$$5 K and a structural transition at $$T^*{simeq}$$147 K. Applying physical or chemical pressure on Sr$$_3$$Ir$$_4$$Sn$$_{13}$$ suppresses $$T^*$$ rapidly, and a quasi-linear $$T$$ dependence of electrical resistivity, signature of non-Fermi liquid behavior, was observed where $$T^*$$ extrapolates to 0 K. The isomorphs (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ exhibits similar behavior, where the criticality can be reached by $$x{sim}$$0.9 without external pressure. Neutron scattering experiments in Sr$$_3$$Ir$$_4$$Sn$$_{13}$$ evidences the second order nature of the structural transition at $$T^*$$ by the observation of a continuous evolution of superlattice peak below $$T^*$$ and a gradual increase of critical scattering upon approaching to $$T^*$$ by cooling. Increase of $$x$$ in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ toward the quantum critical point leads to the systematic variation of the critical exponents of the order parameter. In addition, this substitution induces the phonon softening around the M point towards zero energy revealed by inelastic X-ray scattering experiment. We will present systematic variations in both elastic and inelastic channels upon approaching to the quantum critical point.


Ultralow thermal conductivity from transverse acoustic phonon suppression in distorted crystalline $$alpha$$-MgAgSb

Li, X.*; Liu, P.-F.*; Zhao, E.*; Zhang, Z.*; Guide, T.*; Le, M. D.*; Avdeev, M.*; 池田 一貴*; 大友 季哉*; 古府 麻衣子; et al.

Nature Communications (Internet), 11(1), p.942_1 - 942_9, 2020/02

 被引用回数:2 パーセンタイル:14.76(Multidisciplinary Sciences)



Fine structure in the $$alpha$$ decay of $$^{223}$$U

Sun, M. D.*; Liu, Z.*; Huang, T. H.*; Zhang, W. Q.*; Andreyev, A. N.; Ding, B.*; Wang, J. G.*; Liu, X. Y.*; Lu, H. Y.*; Hou, D. S.*; et al.

Physics Letters B, 800, p.135096_1 - 135096_5, 2020/01

 被引用回数:1 パーセンタイル:30.54(Astronomy & Astrophysics)

Fine structure in the $$alpha$$ decay of $$^{223}$$U was observed in the fusion-evaporation reaction $$^{187}$$Re($$^{40}$$Ar,p3n) by using fast digital pulse processing technique. Two $$alpha$$-decay branches of $$^{223}$$U feeding the ground state and 244 keV excited state of $$^{219}$$Th were identified by establishing the decay chain $$^{223}$$U$$rightarrow$$$$^{219}$$Th$$rightarrow$$$$^{215}$$Ra$$rightarrow$$$$^{211}$$Rn. The $$alpha$$-particle energy for the ground-state to ground-state transition of $$^{223}$$U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62$$^{+14}_{-10} mu$$s. Evolution of nuclear structure for $$N$$=131 even-$$Z$$ isotones from Po to U was discussed in the frameworks of nuclear mass and reduced $$alpha$$-decay width, a weakening octupole deformation in the ground state of $$^{223}$$U relative to its lighter isotones $$^{219}$$Ra and $$^{211}$$Th was suggested.


Comparison of heavy-ion transport simulations; Collision integral with pions and $$Delta$$ resonances in a box

小野 章*; Xu, J.*; Colonna, M.*; Danielewicz, P.*; Ko, C. M.*; Tsang, M. B.*; Wang, Y,-J.*; Wolter, H.*; Zhang, Y.-X.*; Chen, L.-W.*; et al.

Physical Review C, 100(4), p.044617_1 - 044617_35, 2019/10

 被引用回数:15 パーセンタイル:2.38(Physics, Nuclear)



Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n,$$gamma$$) method

藤田 善貴; 関 美沙紀; 滑川 要二*; 西方 香緒里; 木村 明博; 柴田 晃; 佐谷戸 夏紀; 土谷 邦彦; 佐野 忠史*; 藤原 靖幸*; et al.

KURNS Progress Report 2018, P. 155, 2019/08

高濃縮ウランの利用低減や核不拡散及び核セキュリティ、核分裂生成物の処理の観点から放射化法((n,$$gamma$$)法)によるMo-99($$^{99}$$Mo)製造の研究開発が進められている。この方法を$$^{99}$$Mo/$$^{rm 99m}$$Tcジェネレータに適用するためには、Mo吸着剤として広く用いられているアルミナ(Al$$_{2}$$O$$_{3}$$)の特性改善が必要不可欠である。本研究では、4種類のAl$$_{2}$$O$$_{3}$$試料を準備し、照射済MoO$$_{3}$$ペレットを用いて$$^{99}$$Mo吸着および$$^{rm 99m}$$Tc溶離特性を評価した。また、$$^{98}$$Mo濃縮率の異なる3種類のMoO$$_{3}$$ペレットを照射して、生成される$$^{99}$$Mo比放射能を比較した。その結果、$$^{99}$$Mo吸着量はV-B-300が最も優れているとともに、$$^{rm 99m}$$Tc溶離率も約80%と比較的高く、得られる$$^{rm 99m}$$Tc溶離量が最も多いことを明らかにした。$$^{98}$$Mo濃縮率比較では、58.82%の濃縮ペレットで予想放射能量に近かったのに対して、98.5%以上の濃縮ペレットでは予想よりも小さい比放射能が得られた。今後、より高精度な実験方法を検討する必要がある。


Evidence for singular-phonon-induced nematic superconductivity in a topological superconductor candidate Sr$$_{0.1}$$Bi$$_{2}$$Se$$_{3}$$

Wang, J.*; Ran, K.*; Li, S.*; Ma, Z.*; Bao, S.*; Cai, Z.*; Zhang, Y.*; 中島 健次; 河村 聖子; $v{C}$erm$'a$k, P.*; et al.

Nature Communications (Internet), 10, p.2802_1 - 2802_6, 2019/06

 被引用回数:7 パーセンタイル:13.47(Multidisciplinary Sciences)

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 Sr$$_{0.1}$$Bi$$_{2}$$Se$$_{3}$$, a prime candidate for realizing topological superconductivity by doping the topo-logical insulator Bi$$_{2}$$Se$$_{3}$$, we found that there exist singular 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 MxBi$$_{2}$$Se$$_{3}$$ (M = Cu, Sr, Nb) superconductor family. Therefore, we show that these superconductors may be the first examples where electron-phonon interaction can induce more exotic superconducting pairing than the $$s$$-wave.


Passive sweat collection and colorimetric analysis of biomarkers relevant to kidney disorders using a soft microfluidic system

Zhang, Y.*; Guo, H.*; Kim, S. B.*; Wu, Y.*; Ostojich, D.*; Park, S. H.*; Wang, X.*; Weng, Z.*; Li, R.*; Bandodkar, A. J.*; et al.

Lab on a Chip, 19(9), p.1545 - 1555, 2019/05

 被引用回数:20 パーセンタイル:1.78(Biochemical Research Methods)



Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

 被引用回数:2 パーセンタイル:45.7(Physics, Multidisciplinary)

We report neutron scattering measurements of single-crystalline YFe$$_{2}$$Ge$$_{2}$$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe$$_{2}$$Ge$$_{2}$$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe$$_{2}$$Ge$$_{2}$$ displays anisotropic stripe-type antiferromagnetic spin fluctuations at ($$pi, 0, pi$$). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector ($$0, 0, pi$$). These ferromagnetic spin fluctuations are isotropic in the ($$H, K$$) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe$$_{2}$$Ge$$_{2}$$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.


Proton shell evolution below $$^{132}$$Sn; First measurement of low-lying $$beta$$-emitting isomers in $$^{123,125}$$Ag

Chen, Z. Q.*; Li, Z. H.*; Hua, H.*; 渡邉 寛*; Yuan, C. X.*; Zhang, S. Q.*; Lorusso, G.*; Orlandi, R.; 他60名*

Physical Review Letters, 122(21), p.212502_1 - 212502_6, 2019/05

 被引用回数:4 パーセンタイル:25.43(Physics, Multidisciplinary)

$$beta$$-delayed $$gamma$$-ray spectroscopy of the neutron-rich isotopes $$^{123,125}$$Ag was carried out at RIBF, RIKEN. The long predicted 1/2$$^{-}$$ $$beta$$ emitting isomers were identified in both nuclei for the first time. The new experimental results extend the systematic trend of energy spacing between the lowest 9/2$$^+$$ and 1/2$$^{-}$$ levels in Ag isotopes up to N=78, providing a clear signal for the reduction of the Z=40 subshell gap in Ag towards N=82. The tensor force is found to play a key role in the reduction of the Z=40 sub-shell gap.


Mechanism of hardening and damage initiation in oxygen embrittlement of body-centred-cubic niobium

Yang, P.-J.*; Li, Q.-J.*; 都留 智仁; 尾方 成信*; Zhang, J.-W.*; Sheng, H.-W.*; Shan, Z.-W.*; Sha, G.*; Han, W.-Z.*; Li, J.*; et al.

Acta Materialia, 168, p.331 - 342, 2019/04

 被引用回数:11 パーセンタイル:6.69(Materials Science, Multidisciplinary)



Flow-electrode CDI removes the uncharged Ca-UO$$_{2}$$-CO$$_{3}$$ ternary complex from brackish potable groundwater; Complex dissociation, transport, and sorption

Ma, J.*; Zhang, Y.*; Collins, R. N.*; Tsarev, S.*; 青柳 登; Kinsela, A. S.*; Jones, A. M.*; Waite, T. D.*

Environmental Science & Technology, 53(5), p.2739 - 2747, 2019/03

 被引用回数:12 パーセンタイル:7.12(Engineering, Environmental)

Unacceptably high uranium concentrations in decentralized and remote potable groundwater resources, especially those of high hardness, are a common worldwide problem. The complexation of alkali earth metals, carbonate and uranium(VI) results in the formation of thermodynamically stable ternary aqueous species that are predominantly neutrally-charged. The removal of the uncharged (non-adsorbing) complexes is a problematic issue for many water treatment technologies. As such, we have evaluated the efficacy of a recently-developed electrochemical technology, termed flow-electrode capacitive deionization (FCDI), to treat a synthetic groundwater, the composition of which is comparable to groundwater resources in the Northern Territory, Australia. Theoretical calculations and time-resolved laser fluorescence spectroscopy analyses confirmed that the complex was the primary aqueous species followed. Results under different operating conditions demonstrated that FCDI is versatile in reducing uranium concentrations to $$<$$ 10 $$mu$$g L$$^{-1}$$ with low electrical consumption (e.g. $$sim$$ 0.1 kWh m$$^{-3}$$). It is concluded that the capability of FCDI to remove uranium under these common conditions depends on the dissociation kinetics of the complex in the electrical field.


Colossal barocaloric effects in plastic crystals

Li, B.*; 川北 至信; 河村 聖子; 菅原 武*; Wang, H.*; Wang, J.*; Chen, Y.*; 河口 沙織*; 河口 彰吾*; 尾原 幸治*; et al.

Nature, 567(7749), p.506 - 510, 2019/03

 被引用回数:43 パーセンタイル:1.03(Multidisciplinary Sciences)



Application of phosphate modified CAC for incorporation of simulated secondary aqueous wastes in Fukushima Daiichi NPP, 1; Characterization of solidified cementitious systems with reduced water content

Garcia-Lodeiro, I.*; Lebon, R.*; Machoney, D.*; Zhang, B.*; 入澤 啓太; 谷口 拓海; 並木 仁宏*; 大杉 武史; 目黒 義弘; 木下 肇*

Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/11

Processing of contaminated water from Fukushima Daiichi Nuclear Power Plant (NPP) results in a large amount of radioactive aqueous wastes, with a significant amount of radioactive strontium ($$^{90}$$Sr) and inorganic salts (mainly chlorides). It is challenging to condition these wastes using the conventional cementation because of the significant contamination and associated risk of hydrogen gas generation. The present study investigates the applicability of calcium aluminate cement (CAC) modified with phosphates (CAP) for incorporation of simulated secondary aqueous wastes. The use of CAP system is interesting because it may allow the reduction of water content, and the risk of hydrogen gas generation, since the solidification of this systems does not solely rely on the hydration of clinker phases. CAC and CAP pastes were prepared intermixing with different secondary aqueous wastes (concentrated effluent, iron co-precipitation slurry and carbonate slurry) and cured at either 35$$^{circ}$$C or 90$$^{circ}$$C in open systems for 7 days. Overall, the incorporation of the simulated wastes did not significantly alter the development of CAP or CAC, maintaining the integrity of their microstructure. However, because of the high Cl$$^{-}$$ content in the simulated wastes, CAC system showed formation of the Friedel's salt (Ca$$_{2}$$Al(OH)$$_{6}$$Cl(H$$_{2}$$O)$$_{2}$$). On the other hand, formation of chlorapatite-type phase was detected in the CAP systems cured at 90$$^{circ}$$C.


Soft, skin-interfaced microfluidic systems with wireless, battery-free electronics for digital, real-time tracking of sweat loss and electrolyte composition

Kim, S. B.*; Lee, K.-H.*; Raj, M. S.*; Reeder, J. T.*; Koo, J.*; Hourlier-Fargette, A.*; Bandodkar, A. J.*; Won, S. M.*; 関根 由莉奈; Choi, J.*; et al.

Small, 14(45), p.1802876_1 - 1802876_9, 2018/11

 被引用回数:23 パーセンタイル:8.99(Chemistry, Multidisciplinary)



Evidence of a structural quantum critical point in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ from a lattice dynamics study

Cheung, Y. W.*; Hu, Y. J.*; 今井 正樹*; 谷奥 泰明*; 金川 響*; 村川 譲一*; 森山 広大*; Zhang, W.*; Lai, K. T.*; 吉村 一良*; et al.

Physical Review B, 98(16), p.161103_1 - 161103_5, 2018/10

 被引用回数:5 パーセンタイル:47.75(Materials Science, Multidisciplinary)

Approaching a quantum critical point has been an effective route to stabilize superconductivity. While the role of magnetic QCPs has been extensively discussed, similar exploration of a structural QCP is scarce. Using inelastic X-ray scattering, we examine the phonon spectrum of the nonmagnetic quasi-skutterudite (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$, which represents a precious system to explore the interplay between structural instabilities and superconductivity by tuning the Ca concentration x. We unambiguously detect the softening of phonon modes around the M point on cooling towards the structural transition. Intriguingly, at x = 0:85, the soft mode energy squared at the M point extrapolates to zero at -5.7 K, providing the first compelling microscopic evidence of a structural QCP in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$. The enhanced phonon density-of-states at low energy provides the essential ingredient for realizing strong-coupling superconductivity near the structural QCP.


New antiferromagnetic order with pressure-induced superconductivity in EuFe$$_2$$As$$_2$$

池田 修悟*; 土屋 優*; Zhang, X.-W.*; 岸本 俊二*; 亀卦川 卓美*; 依田 芳卓*; 中村 博樹; 町田 昌彦; Glasbrenner, J.*; 小林 寿夫*

Physical Review B, 98(10), p.100502_1 - 100502_6, 2018/09

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)



Investigation of the electronic structure and lattice dynamics of the thermoelectric material Na-doped SnSe

Wu, P.*; Zhang, B.*; Peng, K. L.*; 萩原 雅之*; 石川 喜久*; 古府 麻衣子; Lee, S. H.*; 組頭 広志*; Hu, C. S.*; Qi, Z. M.*; et al.

Physical Review B, 98(9), p.094305_1 - 094305_7, 2018/09

 被引用回数:4 パーセンタイル:55.32(Materials Science, Multidisciplinary)

熱電材料であるNaドープしたSnSeについて、ARPES, 中性子回折, 中性子非弾性散乱でその電子構造と格子ダイナミクスを測定した結果を報告する。


Neutron irradiation effect of high-density MoO$$_{3}$$ pellets for Mo-99 production

藤田 善貴; 西方 香緒里; 滑川 要二*; 木村 明博; 柴田 晃; 佐谷戸 夏紀; 土谷 邦彦; 佐野 忠史*; 藤原 靖幸*; Zhang, J.*

KURRI Progress Report 2017, P. 126, 2018/08



A Fluorometric skin-interfaced microfluidic device and smartphone imaging module for ${{it in situ}}$ quantitative analysis of sweat chemistry

関根 由莉奈; Kim, S. B.*; Zhang, Y.*; Bandodkar, A. J.*; Xu, S.*; Choi, J.*; 入江 将大*; Ray, T. R.*; Kohli, P.*; 香西 直文; et al.

Lab on a Chip, 18(15), p.2178 - 2186, 2018/08

近年、スウェットに含まれる代謝産物やイオン等を用いたPoint of Careが高く注目されている。本研究では、それらのバイオマーカーを効果的にその場で検出することを目的として、ソフトで薄いウェアラブルマイクロ流路デバイスとスマートフォンを基盤とした蛍光イメージングシステムを提案する。精密に設計されたマイクロ流路は、皮膚から汗を時間シーケンス制御で集めることを可能にした。また、集められた汗から蛍光検出剤によって検出された塩化物,ナトリウム,亜鉛濃度をスマートフォンを基盤とした蛍光イメージングシステムで正確に定量分析することに成功した。このシステムを実際に試験したところ、正確に効率よく作動することを確認した。

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