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Triplon band splitting and topologically protected edge states in the dimerized antiferromagnet

那波 和宏*; 田中 公人*; 栗田 伸之*; 佐藤 卓*; 杉山 晴紀*; 植草 秀裕*; 河村 聖子; 中島 健次; 田中 秀数*

Nature Communications (Internet), 10, p.2096_1 - 2096_8, 2019/05



Divalent EuRh$$_2$$Si$$_2$$ as a reference for the Luttinger theorem and antiferromagnetism in trivalent heavy-fermion YbRh$$_2$$Si$$_2$$

G$"u$ttler, M.*; Generalov, A.*; 藤森 伸一; Kummer, K.*; Chikina, A.*; Seiro, S.*; Danzenb$"a$cher, S.*; Koroteev, Yu. M.*; Chulkov, E. V.*; Radovic, M.*; et al.

Nature Communications (Internet), 10(1), p.796_1 - 796_7, 2019/02

 パーセンタイル:100(Multidisciplinary Sciences)

Application of the Luttinger Theorem (LT) to the canonical heavy-fermion Kondo Lattice (KL) material YbRh$$_2$$Si$$_2$$ suggests that its large 4f-derived Fermi surface (FS) in the paramagnetic (PM) regime should be similar in shape and volume to that of the divalent local moment anti-ferromagnet (AFM) EuRh$$_2$$Si$$_2$$ in its PM regime. This leads to the tempting opportunity to explore a new experimental realization of the LT in general and how the large FS may change upon the AFM transition below 70 mK in YbRh$$_2$$Si$$_2$$ in particular. A detailed knowledge of the FS reconstruction might be essential to disclose the properties of this phase, which is a precursor of quantum criticality and superconductivity. Using angle-resolved photoemission spectroscopy (ARPES), we observe a large FS for PM EuRh$$_2$$Si$$_2$$ essentially the same as the one seen in YbRh$$_2$$Si$$_2$$ in the KL state at a temperature of 1 K. Across the EuRh$$_2$$Si$$_2$$ AFM transition we found an extensive fragmentation of the FS due to Brillouin zone folding, intersection and resulting hybridization of the Doughnut and Jungle gym Fermi-surface sheets. Our results on EuRh$$_2$$Si$$_2$$ indicate that the formation of the AFM state in YbRh$$_2$$Si$$_2$$ is very likely also connected with large changes in the FS, which have to be taken into account in the controversial analysis and discussion of anomalies observed at the quantum critical point in this system.


Hydrogen-based metabolism as an ancestral trait in lineages sibling to the Cyanobacteria

Carnevali, P. B. M.*; Schulz, F.*; Castelle, C. J.*; Kantor, R. S.*; Shih, P. M.*; Sharon, I.*; Santini, J.*; Olm, M. R.*; 天野 由記; Thomas, B. C.*; et al.

Nature Communications (Internet), 10, p.463_1 - 463_15, 2019/01

 被引用回数:1 パーセンタイル:14.78(Multidisciplinary Sciences)

The metabolic platform in which microbial aerobic respiration evolved is tightly linked to the origins of Cyanobacteria (Oxyphotobacteria). Melainabacteria and Sericytochromatia, close phylogenetic neighbores to Oxyphotobacteria comprise both fermentative and aerobic representatives, or clades that are capablee of both. Here, we predict the metabolisms of Margulisbacteria from two distinct environments and Saganbacteria, and compare them to genomes of organisms from the related lineages. Melainabacteria BJ4A obtained from Mizunami site are potentially able to use O$$_{2}$$ and other terminal electron acceptors. The type C heme-copper oxygen reductase found in Melainabacteria BJ4A may be adapted to low O$$_{2}$$ levels, as expected for microaerophilic or anoxic environments such as the subsurface. Notably, Melainabacteria BJ4A seems to have a branched electron transport chain, with one branch leading to a cytochrome d ubiquinol oxidoreductase and the other one leading to the type C heme-copper oxygen reductase. Both these enzymes have high affinity for O$$_{2}$$, thus are adapted to low O$$_{2}$$ levels. These contemporary lineages have representatives with fermentative H$$_{2}$$-based metabolism, lineages capable of aerobic or anaerobic respiration, and lineages with both. Our findings support the idea that the ancestor of these lineages was an anaerobe in which fermentation and H$$_{2}$$ metabolism were central metabolic features.


Vortex rectenna powered by environmental fluctuations

Lustikova, J.*; 塩見 雄毅*; 横井 直人*; 壁谷 典幸*; 木村 憲彰*; 家永 紘一郎*; 金子 真一*; 大熊 哲*; 高橋 三郎*; 齊藤 英治

Nature Communications (Internet), 9, p.4922_1 - 4922_6, 2018/11

 被引用回数:1 パーセンタイル:47.22(Multidisciplinary Sciences)

A rectenna, standing for a rectifying antenna, is an apparatus which generates d.c. electricity from electric fluctuations. It is expected to realize wireless power transmission as well as energy harvesting from environmental radio waves. To realize such rectification, devices that are made up of internal atomic asymmetry such as an asymmetric junction have been necessary so far. Here we report a material that spontaneously generates electricity by rectifying environmental fluctuations without using atomic asymmetry. The sample is a common superconductor without lowered crystalline symmetry, but, just by putting it in an asymmetric magnetic environment, it turns into a rectifier and starts generating electricity. Superconducting vortex strings only annihilate and nucleate at surfaces, and this allows the bulk electrons to feel surface fluctuations in an asymmetric environment: a vortex rectenna. The rectification and generation can be switched on and off with only a slight change in temperature or external magnetic fields.


Spherical neutron polarimetry under high pressure for a multiferroic delafossite ferrite

寺田 典樹*; Qureshi, N.*; Chapon, L. C.*; 長壁 豊隆

Nature Communications (Internet), 9, p.4368_1 - 4368_9, 2018/10

 パーセンタイル:100(Multidisciplinary Sciences)

We have succeeded in carrying out the first spherical neutron polarimetry (SNP) experiments in conjunction with the application of pressure, working with the multiferroic delafossite CuFeO$$_{2}$$ and using the newly developed nonmagnetic hybrid anvil high pressure cell (HAC). This work determined the detailed magnetic structures in the pressure-induced ferroelectric phases of this material, as well as nonpolar phases at ambient pressure. The present study provides evidence that SNP measurements are viable even in combination with high pressure conditions.


Improving atomic displacement and replacement calculations with physically realistic damage models

Nordlund, K.*; Zinkle, S. J.*; Sand, A. E.*; Granberg, F.*; Averback, R. S.*; Stoller, R.*; 鈴土 知明; Malerba, L.*; Banhart, F.*; Weber, W. J.*; et al.

Nature Communications (Internet), 9, p.1084_1 - 1084_8, 2018/03

 被引用回数:21 パーセンタイル:1.16(Multidisciplinary Sciences)



Maximizing $$T_c$$ by tuning nematicity and magnetism in FeSe$$_{1-x}$$S$$_x$$ superconductors

松浦 康平*; 水上 雄太*; 新井 佑基*; 杉村 優一*; 前島 尚行*; 町田 晃彦*; 綿貫 徹*; 福田 竜生; 矢島 健*; 広井 善二*; et al.

Nature Communications (Internet), 8, p.1143_1 - 1143_6, 2017/10

 被引用回数:16 パーセンタイル:12.89(Multidisciplinary Sciences)

A fundamental issue concerning iron-based superconductivity is the roles of electronic nematicity and magnetism in realising high transition temperature ($$T_c$$). To address this issue, FeSe is a key material, as it exhibits a unique pressure phase diagram involving nonmagnetic nematic and pressure-induced antiferromagnetic ordered phases. However, as these two phases in FeSe have considerable overlap, how each order affects superconductivity remains perplexing. Here we construct the three-dimensional electronic phase diagram, temperature ($$T$$) against pressure ($$P$$) and iso-valent S-substitution ($$x$$), for FeSe$$_{1-x}$$S$$_x$$. By simultaneously tuning chemical and physical pressures, against which the chalcogen height shows a contrasting variation, we achieve a complete separation of nematic and antiferromagnetic phases. In between, an extended nonmagnetic tetragonal phase emerges, where $$T_c$$ shows a striking enhancement. The completed phase diagram uncovers that high-$$T_c$$ superconductivity lies near both ends of the dome-shaped antiferromagnetic phase, whereas $$T_c$$ remainslow near the nematic critical point.


Structure of the magnetic excitations in the spin-1/2 triangular-lattice Heisenberg antiferromagnet Ba$$_{3}$$CoSb$$_{2}$$O$$_{9}$$

伊藤 沙也*; 栗田 伸之*; 田中 秀数*; 河村 聖子; 中島 健次; 伊藤 晋一*; 桑原 慶太郎*; 加倉井 和久*

Nature Communications (Internet), 8, p.235_1 - 235_6, 2017/08

 被引用回数:11 パーセンタイル:18.76(Multidisciplinary Sciences)

A spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) is a prototypical frustrated quantum magnet, which exhibits remarkable quantum many-body effects that arise from the synergy between spin frustration and quantum fluctuation. The ground-state properties of a spin-1/2 TLHAF are theoretically well understood. However, magnetic excitations are less well understood and the theoretical consensus is limited. The experimental study of the magnetic excitations in spin-1/2 TLHAFs has also been limited. Here we show the whole picture of magnetic excitations in the spin-1/2 TLHAF Ba$$_{3}$$CoSb$$_{2}$$O$$_{9}$$ investigated by inelastic neutron scattering. Significantly different from the theory, the excitation spectra have a three-stage energy structure. The lowest first stage is composed of dispersion branches of single-magnon excitations. The second and third stages are dispersive continua accompanied by columnar continuum extending above 10 meV, which is six times larger than the exchange interaction J=1.67 meV. Our results indicate the necessity of a new theoretical framework.


Non-aqueous selective synthesis of orthosilicic acid and its oligomers

五十嵐 正安*; 松本 朋浩*; 八木橋 不二夫*; 山下 浩*; 大原 高志; 花島 隆泰*; 中尾 朗子*; 茂吉 武人*; 佐藤 一彦*; 島田 茂*

Nature Communications (Internet), 8, p.140_1 - 140_8, 2017/07

 被引用回数:2 パーセンタイル:69.79(Multidisciplinary Sciences)

Orthosilicic acid (Si(OH)$$_{4}$$) and its small condensation compounds are among the most important silicon compounds but have never been isolated, despite the long history of intense research due to their instability. These compounds would be highly useful building blocks for advanced materials if they become available at high purity. We developed a simple procedure to selectively synthesize orthosilicic acid, its dimer, cyclic trimer, and tetramer, as well as appropriate conditions to stabilize these species, in organic solvents. Isolation of orthosilicic acid, the dimer and the cyclic tetramer as hydrogen-bonded crystals with tetrabutylammonium halides and of the cyclic trimer as solvent-containing crystals was achieved. The solid-state structures of these compounds were unambiguously clarified by single crystal X-ray diffraction analysis and also by neutron diffraction study for orthosilicic acid. Based on these results, we also succeeded in developing a more practical synthetic procedure for high concentrations of stable orthosilicic acid stably in organic solvents via a simple hydrolysis of tetraalkoxysilanes.


Polar rotor scattering as atomic-level origin of low mobility and thermal conductivity of perovskite CH$$_{3}$$NH$$_{3}$$PbI$$_{3}$$

Li, B.; 川北 至信; Liu, Y.*; Wang, M.*; 松浦 直人*; 柴田 薫; 河村 聖子; 山田 武*; Lin, S.*; 中島 健次; et al.

Nature Communications (Internet), 8, p.16086_1 - 16086_9, 2017/06

 被引用回数:24 パーセンタイル:6.04(Multidisciplinary Sciences)

Perovskite CH$$_{3}$$NH$$_{3}$$PbI$$_{3}$$ 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 approximately 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.


Hydrogenation of iron in the early stage of Earth's evolution

飯塚 理子*; 八木 健彦*; 後藤 弘匡*; 奥地 拓生*; 服部 高典; 佐野 亜沙美

Nature Communications (Internet), 8, p.14096_1 - 14096_7, 2017/01


 被引用回数:9 パーセンタイル:22.34(Multidisciplinary Sciences)



Thermal imaging of spin Peltier effect

大門 俊介*; 井口 亮*; 日置 友智*; 齊藤 英治; 内田 健一*

Nature Communications (Internet), 7, p.13754_1 - 13754_7, 2016/12

 被引用回数:27 パーセンタイル:7.61(Multidisciplinary Sciences)

The Peltier effect modulates the temperature of a junction comprising two different conductors in response to charge currents across the junction, which is used in solid-state heat pumps and temperature controllers in electronics. Recently, in spintronics, a spin counterpart of the Peltier effect was observed. The "spin Peltier effect" modulates the temperature of a magnetic junction in response to spin currents. Here we report thermal imaging of the spin Peltier effect; using active thermography technique, we visualize the temperature modulation induced by spin currents injected into a magnetic insulator from an adjacent metal. The thermal images reveal characteristic distribution of spin-current-induced heat sources, resulting in the temperature change confined only in the vicinity of themetal/insulator interface. This finding allows us to estimate the actual magnitude of the temperature modulation induced by the spin Peltier effect, which is more than one order of magnitude greater than previously believed.


Spontaneous decays of magneto-elastic excitations in non-collinear antiferromagnet (Y,Lu)MnO$$_{3}$$

Oh, J.*; Le, M. D.*; Nahm, H.-H.*; Sim, H.*; Jeong, J.*; Perring, T. G.*; Woo, H.*; 中島 健次; 河村 聖子; Yamani, Z.*; et al.

Nature Communications (Internet), 7, p.13146_1 - 13146_6, 2016/10

 被引用回数:14 パーセンタイル:14.01(Multidisciplinary Sciences)



Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

Frandsen, B. A.*; Liu, L.*; Cheung, S. C.*; Guguchia, Z.*; Khasanov, R.*; Morenzoni, E.*; Munsie, T. J. S.*; Hallas, A. M.*; Wilson, M. N.*; Cai, Y.*; et al.

Nature Communications (Internet), 7, p.12519_1 - 12519_8, 2016/08

 被引用回数:7 パーセンタイル:39.63(Multidisciplinary Sciences)

RENiO$$_3$$ (RE = rare-earth element) and V$$_2$$O$$_3$$ are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO$$_3$$) or pressure (V$$_2$$O$$_3$$), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation experiments that the QPT in RENiO$$_3$$ and V$$_2$$O$$_3$$ is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition.


Spin-current probe for phase transition in an insulator

Qiu, Z.*; Li, J.*; Hou, D.*; Arenholz, E.*; N'Diaye, A. T.*; Tan, A.*; 内田 健一*; 佐藤 浩司*; 岡本 聡*; Tserkovnyak, Y.*; et al.

Nature Communications (Internet), 7, p.12670_1 - 12670_6, 2016/08

 被引用回数:50 パーセンタイル:2.81(Multidisciplinary Sciences)

Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is a flux of spin without an electric charge and its transport reflects spin excitation. We demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices.


Observation of temperature-gradient-induced magnetization

Hou, D.*; Qiu, Z.*; 井口 亮*; 佐藤 浩司*; Vehstedt, E. K.*; 内田 健一*; Bauer, G. E. W.*; 齊藤 英治

Nature Communications (Internet), 7, p.12265_1 - 12265_6, 2016/07

 被引用回数:6 パーセンタイル:32.76(Multidisciplinary Sciences)

Applying magnetic fields has been the method of choice to magnetize non-magnetic materials, but they are difficult to focus. The magneto-electric effect and voltage-induced magnetization generate magnetization by applied electric fields, but only in special compounds or heterostructures. Here we demonstrate that a simple metal such as gold can be magnetized by a temperature gradient or magnetic resonance when in contact with a magnetic insulator by observing an anomalous Hall-like effect, which directly proves the breakdown of time-reversal symmetry. Such Hall measurements give experimental access to the spectral spin Hall conductance of the host metal, which is closely related to other spin caloritronics phenomena such as the spin Nernst effect and serves as a reference for theoretical calculation.


Origin of the spin Seebeck effect in compensated ferrimagnets

Gepr$"a$gs, S.*; Kehlberger, A.*; Coletta, F.*; Qiu, Z.*; Guo, E.-J.*; Schulz, T.*; Mix, C.*; Meyer, S.*; Kamra, A.*; Althammer, M.*; et al.

Nature Communications (Internet), 7, p.10452_1 - 10452_6, 2016/02

 被引用回数:49 パーセンタイル:3.02(Multidisciplinary Sciences)

Magnons are the elementary excitations of a magnetically ordered system. Here, we show that the spin Seebeck effect is sensitive to the complexities of the magnon spectrum. The spin Seebeck effect is caused by a thermally excited spin dynamics that is converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the spin Seebeck effect in the ferrimagnet gadlinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that high-energy exchange magnons play a key role in the spin Seebeck effect.


Carrier-mediated ferromagnetism in the magnetic topological insulator Cr-doped (Sb,Bi)$$_{2}$$Te$$_{3}$$

Ye, M.*; Li, W.*; Zhu, S.-Y.*; 竹田 幸治; 斎藤 祐児; Wang, J.*; Pan, H.*; Nurmamat, M.*; 角田 一樹*; Ji, F.*; et al.

Nature Communications (Internet), 6, p.8913_1 - 8913_7, 2015/11


 被引用回数:18 パーセンタイル:15.31(Multidisciplinary Sciences)



Single-photon emitting diode in silicon carbide

Lohrmann, A.*; 岩本 直也*; Bodrog, Z.*; Castelletto, S.*; 大島 武; Karle, T. J.*; Gali, A.*; Prawer, S.*; McCallum, J. C.*; Johnson, B. C.*

Nature Communications (Internet), 6, p.7783_1 - 7783_7, 2015/07

 被引用回数:54 パーセンタイル:4.09(Multidisciplinary Sciences)

A new single photon source (SPS) was found in hexagonal silicon carbide (SiC), and the luminescence from the SPS could be controlled by the operation of the pn diode. The SPS showed electro-luminescence (EL) with spectra between 700 and 850 nm (zero phonon line: 745 nm) and the EL could be easily observed at even room temperature (RT). Also, the SPS has very high thermal stability and can be observed even after 1800 $$^{circ}$$C annealing. The luminescence from the SPS was also observed by photo-luminescence measurements at RT. From Ab initio calculation, it was proposed that the silicon antisite defects beneath cubic SiC inclusion are a reasonable structure for the SPS although the identification of the SPS has not yet done.


Generation of spin currents by surface plasmon resonance

内田 健一*; 安立 裕人; 菊池 大介*; 伊藤 俊*; Qiu, Z.*; 前川 禎通; 齊藤 英治

Nature Communications (Internet), 6, p.5910_1 - 5910_8, 2015/01

 被引用回数:26 パーセンタイル:11.75(Multidisciplinary Sciences)

Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light; electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ interface.

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