研究者詳細 - 後藤　秀徳

論文 - 後藤　秀徳

分割表示 102 件中 41 - 60 件目／全件表示 >>

Superconducting properties of (NH3)yLixFeSe0.5Te0.5 under pressure 査読

Xiaofan Yang, Tong He, Tomoya Taguchi, Huan Li, Yanan Wang, Hidenori Goto, Ritsuko Eguchi, Takafumi Miyazaki, Hitoshi Yamaoka, Hirofumi Ishii, Yen Fa Liao, Yoshihiro Kubozono

New Journal of Physics 21 ( 11 ) 113010 2019年11月

Preparation and characterization of superconducting Ba1-xCsxTi2Sb2O, and its pressure dependence of superconductivity 査読

Wang Yanan, Yang Xiaofan, Taguchi Tomoya, Li Huan, He Tong, Goto Hidenori, Eguchi Ritsuko, Miyazaki Takafumi, Liao Yen-Fa, Ishii Hirofumi, Kubozono Yoshihiro

JAPANESE JOURNAL OF APPLIED PHYSICS 58 ( 11 ) 110603-1 - 110603-7 2019年10月

Superconducting behavior of a new metal iridate compound, SrIr2, under pressure 査読

Xiaofan Yang, Huan Li, Tong He, Tomoya Taguchi, Yanan Wang, Hidenori Goto, Ritsuko Eguchi, Rie Horie, Kazumasa Horigane, Kaya Kobayashi, Jun Akimitsu, Hirofumi Ishii, Yen Fa Liao, Hitoshi Yamaoka, Yoshihiro Kubozono

Journal of Physics Condensed Matter 32 ( 2 ) 2019年10月

Pressure-induced superconductivity in Bi2-xSbxTe3-ySey 査読

Tong He, Xiaofan Yang, Tomoya Taguchi, Teppei Ueno, Kaya Kobayashi, Jun Akimitsu, Hitoshi Yamaoka, Hirofumi Ishii, Yen Fa Liao, Hiromi Ota, Hidenori Goto, Ritsuko Eguchi, Kensei Terashima, Takayoshi Yokoya, Harald O. Jeschke, Xianxin Wu, Yoshihiro Kubozono

Physical Review B 100 ( 9 ) 094525-1 - 094525-11 2019年9月

Fabrication of flexible high-performance organic field-effect transistors using phenacene molecules and their application toward flexible CMOS inverters 査読

Emanuela Pompei, Claudio Turchetti, Shino Hamao, Akari Miura, Hidenori Goto, Hideki Okamoto, Akihiko Fujiwara, Ritsuko Eguchi, Yoshihiro Kubozono

Journal of Materials Chemistry C 7 ( 20 ) 6022 - 6033 2019年4月

Fermi level tuning of Ag-doped Bi2Se3 topological insulator 査読

Eri Uesugi, Takaki Uchiyama, Hidenori Goto, Hiromi Ota, Teppei Ueno, Hirokazu Fujiwara, Kensei Terashima, Takayoshi Yokoya, Fumihiko Matsui, Jun Akimitsu, Kaya Kobayashi, Yoshihiro Kubozono

Scientific Reports 9 ( 1 ) 5376 2019年3月

Synthesis of the extended phenacene molecules, [10]phenacene and [11]phenacene, and their performance in a field-effect transistor 査読

Hideki Okamoto, Shino Hamao, Ritsuko Eguchi, Hidenori Goto, Yasuhiro Takabayashi, Paul Yu, Hsiang Yen, Luo Uei Liang, Chia Wei Chou, Germar Hoffmann, Shin Gohda, Hisako Sugino, Yen Fa Liao, Hirofumi Ishii, Yoshihiro Kubozono

Scientific Reports 9 ( 1 ) 4009 2019年3月

Materials for organic electronics and bioelectronics

Yoshihiro Kubozono, Hidenori Goto, Hiroko Yamada

3d Local Structure And Functionality Design Of Materials 173 - 195 2018年12月

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：World Scientific Publishing Co.

In this chapter, the principles behind the mechanism of operation of organic transistors are described, as they are both important in their own right and also a representative example of organic electronics. Accordingly, the recent progress in organic transistors will be explored in depth. The term “organic transistor” generally refers to the field-effect transistor (FET), which uses thin films of organic materials. The study of these “organic FETs” began in the 1980s.1 Initially, the available fieldeffect mobility (µ), which is one determinant of the performance of an FET, was ca. 10-5 cm2 V-1 s-1, a value that is insufficient for practical applications. In the late 1990s, it was found that pentacene, in which five benzene rings are connected in a linear structure (Fig. 8.1.1), and C60, in which 60 carbon atoms form a spherical structure, were good candidates for the active layer of an FET device. The µ value became ~1 cm2 V-1 s-1 in FETs using these molecules.2, 3 This µ value raised the expectation that organic FETs might in the future become practical devices. On the other hand, since the year 2000, some work on FETs has demonstrated that the physical properties of materials can be controlled by carrier accumulation, such as the field-induced carrier doping of C60 for inducing superconductivity. These studies were not the case, but the interest in field-induced carrier doping to control the physical properties of materials has attracted much attention from researchers in solid-state physics. Consequently, some control of the physical properties of inorganic materials has been achieved by field-induced carrier accumulation using a device with the structure of an FET.4, 5 Research on organic FETs has been brought to a new stage by the participation of many researchers from other fields, where FET performance was pursued not only to find practical applications, but also to investigate fundamental physics. In 2003, a device with excellent FET properties that used a single crystal was fabricated using rubrene (Fig. 8.1.1).6 This showed that transistor operation in an organic FET could be achieved using not only thin films but also single crystals. An FET using a single crystal is superior to a thin-film FET for studying the intrinsic nature of organic materials because many interfering factors such as structural defects, grain boundaries, and impurities can be removed from the active layer. Generally, FET performance is also higher in a single-crystal FET than in a thin-film FET. Clearly, these studies have led to remarkable advances in the research on organic FETs. Furthermore, Hall-effect measurements were achieved in single crystals of organic molecules, 7, 8 and angle-resolved photoemission spectroscopy (ARPES) was performed on some organic single crystals.9, 10 Based on these results, it was suggested that electron transport in organic singlecrystal FETs occurs by band transport rather than hopping transport. Since then, the idea that electron transport in an organic thin-film FET is explained by simple hopping transport has been modified due to analyses based on the multiple shallow trap-and-release (MTR) model for the temperature-dependence of transport properties in organic thinfilm FETs exhibiting a high µ value.11-13 The MTR model assumes that the carriers in a band are captured by trap states and thermally excited up to the conduction (or valence) band, i.e. this concept is substantially based on band transport. Furthermore, the reduction of µ value caused by thermal scattering of phonons was determined from the temperature-dependence of µ in organic single-crystal FETs.14, 15 This constituted the direct observation of band transport in organic single-crystal FETs. These studies have enabled the full discussion of the mechanism of organic FET operation. An FET using pentacene (Fig. 8.1.1) as the active layer shows typical pchannel operation with Au source/drain electrodes, but shows n-channel operation with Ca source/drain electrodes.16 So an organic FET can operate both as p-channel and n-channel depending on the electrode metal, a flexibility termed “ambipolar”. Thus, an organic FET can operate in an ambipolar way by changing the metal of the source/drain electrodes (or changing the work function of the electrodes), unlike the operation of Si MOSFETs, which can operate in either p-channel or n-channel through the formation of an inversion layer in which minority carriers in the bulk become the majority in the channel region. Also, neither organic thin films nor crystals are doped with any impurities, unlike the Si crystal used in Si MOSFETs, which can be doped with an acceptor (p-type Si) or with a donor (n-type Si) material. In Section 8.1.1, we will fully examine organic FETs based on the background described above.

DOI： 10.1142/9789813273672_0010

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Preparation and characterization of a new metal-intercalated graphite superconductor 査読

Yang Xiaofan, Taguchi Tomoya, Wang Yanan, He Tong, Uchiyama Takaki, Takai Akihisa, Zhi Lei, Miyazaki Takafumi, Goto Hidenori, Eguchi Ritsuko, Ishii Hirofumi, Liao Yen-Fa, Yamaoka Hitoshi, Kubozono Yoshihiro

MATERIALS RESEARCH EXPRESS 6 ( 1 ) 016003 2018年10月

Pressure dependence of superconductivity in low- and high- T c phases of (NH3)yNaxFeSe 査読

Takahiro Terao, Xiaofan Yang, Xiao Miao, Lu Zheng, Hidenori Goto, Takafumi Miyazaki, Hitoshi Yamaoka, Hirofumi Ishii, Yen-Fa Liao, Yoshihiro Kubozono

Physical Review B 97 ( 9 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Physical Society

We prepared two superconducting phases, which are called "low-Tc phase" and "high-Tc phase" of (NH3)yNaxFeSe showing Tc's of 35 and 44 K, respectively, at ambient pressure, and studied the superconducting behavior and structure of each phase under pressure. The Tc of the 35 K at ambient pressure rapidly decreases with increasing pressure up to 10 GPa, and it remains unchanged up to 22 GPa. Finally, superconductivity was not observed down to 1.4 K at 29 GPa, i.e., Tc&lt
1.4K. The Tc of the 44 K phase also shows a monotonic decrease up to 15 GPa and it weakly decreases up to 25 GPa. These behaviors suggest no pressure-driven high-Tc phase (called "SC-II") between 0 and 25 GPa for the low-Tc and high-Tc phases of (NH3)yNaxFeSe, differing from the behavior of (NH3)yCsxFeSe, which has a pressure-driven high-Tc phase (SC-II) in addition to the superconducting phase (SC-I) observed at ambient and low pressures. The Tc-c phase diagram for both low-Tc and high-Tc phases shows that the Tc can be linearly scaled with c (or FeSe plane spacing), where c is a lattice constant. The reason why a pressure-driven high-Tc phase (SC-II) was found for neither low-Tc nor high-Tc phases of (NH3)yNaxFeSe is fully discussed, suggesting a critical c value as the key to forming the pressure-driven high-Tc phase (SC-II). Finally, the precise Tc-c phase diagram is depicted using the data obtained thus far from FeSe codoped with a metal and NH3 or amine, indicating two distinct Tc-c lines below c=17.5Å.

DOI： 10.1103/PhysRevB.97.094505

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Pressure-induced superconductivity in AgxBi2-xSe3 査読

Tong He, Xiaofan Yang, Takahiro Terao, Takaki Uchiyama, Teppei Ueno, Kaya Kobayashi, Jun Akimitsu, Takafumi Miyazaki, Takumi Nishioka, Koji Kimura, Kouichi Hayashi, Naohisa Happo, Hitoshi Yamaoka, Hirofumi Ishii, Yen-Fa Liao, Hiromi Ota, Hidenori Goto, Yoshihiro Kubozono

Physical Review B 97 ( 10 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Physical Society

We investigated the pressure dependence of electric transport and crystal structure of Ag-doped Bi2Se3. In the sample prepared by Ag doping of Bi2Se3, the Bi atom was partially replaced by Ag, i.e., Ag0.05Bi1.95Se3. X-ray diffraction patterns of Ag0.05Bi1.95Se3 measured at 0-30 GPa showed three different structural phases, with rhombohedral, monoclinic, and tetragonal structures forming in turn as pressure increased, and structural phase transitions at 8.8 and 24 GPa. Ag0.05Bi1.95Se3 showed no superconductivity down to 2.0 K at 0 GPa, but under pressure, superconductivity suddenly appeared at 11 GPa. The magnetic field (H) dependence of the superconducting transition temperature Tc was measured at 11 and 20.5 GPa, in order to investigate whether the pressure-induced superconducting phase is explained by either p-wave polar model or s-wave model.

DOI： 10.1103/PhysRevB.97.104503

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Preparation and characterization of a new graphite superconductor: Ca0.5Sr0.5C6 査読

Saki Nishiyama, Hidenori Fujita, Masatoshi Hoshi, Xiao Miao, Takahiro Terao, Xiaofan Yang, Takafumi Miyazaki, Hidenori Goto, Tomoko Kagayama, Katsuya Shimizu, Hitoshi Yamaoka, Hirofumi Ishii, Yen-Fa Liao, Yoshihiro Kubozono

SCIENTIFIC REPORTS 7 2017年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

We have produced a superconducting binary-elements intercalated graphite, CaxSr1-xCy, with the intercalation of Sr and Ca in highly-oriented pyrolytic graphite; the superconducting transition temperature, T(c1)was similar to 3 K. The superconducting CaxSr1-xCy sample was fabricated with the nominal x value of 0.8, i.e., Ca0.8Sr0.2Cy. Energy dispersive X-ray (EDX) spectroscopy provided the stoichiometry of Ca0.5(2)Sr0.5(2)C-y for this sample, and the X-ray powder diffraction (XRD) pattern showed that Ca0.5(2)Sr0.5(2)Cy took the SrC6-type hexagonal-structure rather than CaC6-type rhombohedral-structure. Consequently, the chemical formula of CaxSr1-xCy sample could be expressed as 'Ca0.5(2)Sr0.5(2)C6'. The XRD pattern of Ca0.5(2)Sr0.5(2)C6 was measured at 0-31 GPa, showing that the lattice shrank monotonically with increasing pressure up to 8.6 GPa, with the structural phase transition occurring above 8.6 GPa. The pressure dependence of Tc was determined from the DC magnetic susceptibility and resistance up to 15 GPa, which exhibited a positive pressure dependence of T-c up to 8.3 GPa, as in YbC6, SrC6, KC8, CaC6 and Ca0.6K0.4C8. The further application of pressure caused the rapid decrease of Tc. In this study, the fabrication and superconducting properties of new binary-elements intercalated graphite, CaxSr1-xCy, are fully investigated, and suitable combinations of elements are suggested for binaryelements intercalated graphite.

DOI： 10.1038/s41598-017-07763-y

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Preparation of new superconductors by metal doping of two-dimensional layered materials using ethylenediamine 査読

Xiao Miao, Takahiro Terao, Xiaofan Yang, Saki Nishiyama, Takafumi Miyazaki, Hidenori Goto, Yoshihiro Iwasa, Yoshihiro Kubozono

PHYSICAL REVIEW B 96 ( 1 ) 2017年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We have studied new superconductors prepared by metal doping of two-dimensional (2D) layered materials, FeSe and FeSe0.5Te0.5, using ethylenediamine (EDA). The superconducting transition temperatures (T(c)s) of metal-doped FeSe and metal-doped FeSe0.5Te0.5, i.e., (EDA)(y)MxFeSe and (EDA)(y)MxFeSe0.5Te0.5 (M: Li, Na, and K), were 31-45 K and 19-25 K, respectively. The stoichiometry of each sample was clarified by energy dispersive x-ray (EDX) spectroscopy, and the x-ray powder diffraction pattern indicated a large expansion of lattice constant c, indicating the cointercalation of metal atoms and EDA. The pressure dependence of superconductivity in (EDA)(y)NaxFeSe0.5Te0.5 has been investigated at a pressure of 0-0.8GPa, showing negative pressure dependence in the same manner as (NH3)(y)NaxFeSe0.5Te0.5. The T-c-c phase diagrams of MxFeSe and MxFeSe0.5Te0.5 were drawn afresh from the T-c and c of (EDA)(y)MxFeSe and (EDA)(y)MxFeSe0.5Te0.5, showing that the T-c increases with increasing c but that extreme expansion of c reverses the T-c trend.

DOI： 10.1103/PhysRevB.96.014502

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Transistor properties of exfoliated single crystals of 2H-Mo(Se1-x Te-x) 2 ( 0 <= x <= 1) 査読

Eri Uesugi, Xiao Miao, Hiromi Ota, Hidenori Goto, Yoshihiro Kubozono

PHYSICAL REVIEW B 95 ( 24 ) 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Field-effect transistors (FETs) were fabricated using exfoliated single crystals of Mo(Se1-x Te-x)(2) with an x range of 0 to 1, and the transistor properties fully investigated at 295 K in four-terminal measurement mode. The chemical composition and crystal structure of exfoliated single crystals were identified by energy-dispersive x-ray spectroscopy (EDX), single-crystal x-ray diffraction, and Raman scattering, suggesting the 2H - structure in all Mo(Se1-x Te-x)(2). The lattice constants of a and c increase monotonically with increasing x, indicating the substitution of Se by Te. When x < 0.4 in a FET with a thin single crystal of Mo(Se1-x Te-x)(2), n-channel FET properties were observed, changing to p-channelor ambipolar operation for x > 0.4. In contrast, the polarity of a thick single-crystal Mo(Se1-x Te-x)(2) FET did not change despite an increase in x. The change of polarity in a thin single-crystal FET was well explained by the variation of electronic structure. The absence of such change in the thick single-crystal FET can be reasonably interpreted based on the large bulk conduction due to naturally accumulated electrons. The mu value in the thin single-crystal FET showed a parabolic variation, with a minimum mu at around x = 0.4, which probably originates from the disorder of the single crystal caused by the partial replacement of Se by Te, i.e., a disorder that may be due to ionic size difference of Se and Te.

DOI： 10.1103/PhysRevB.95.245310

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Electrostatic electron-doping yields superconductivity in LaOBiS2 査読

Eri Uesugi, Saki Nishiyama, Hidenori Goto, Hiromi Ota, Yoshihiro Kubozono

APPLIED PHYSICS LETTERS 109 ( 25 ) 2016年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Electrostatic carrier-doping is attracting serious attention as a meaningful technique for producing interesting electronic states in two-dimensional (2D) layered materials. Ionic-liquid gating can provide the critical carrier density required to induce the metal-insulator transition and superconductivity. However, the physical properties of only a few materials have been controlled by the electrostatic carrier-doping during the past decade. Here, we report an observation of superconductivity in a 2D layered material, LaOBiS2, achieved by the electrostatic electron-doping. The electron doping of LaOBiS2 induced metallic conductivity in the normally insulating LaOBiS2, ultimately led to superconductivity. The superconducting transition temperature, T-c, was 3.6 K, higher than the 2.7K seen in LaO1-xFxBiS2 with an electron-doped BiS2 layer. A rapid drop in resistance (R) was observed at low temperature, which disappeared with the application of high magnetic fields, implying a superconducting state. This study reveals that electron-doping is an important technique for inducing superconductivity in 2D layered BiS2 materials. Published by AIP Publishing.

DOI： 10.1063/1.4972400

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Photoelectron Holographic Atomic Arrangement Imaging of Cleaved Bimetal-intercalated Graphite Superconductor Surface 査読

Fumihiko Matsui, Ritsuko Eguchi, Saki Nishiyama, Masanari Izumi, Eri Uesugi, Hidenori Goto, Tomohiro Matsushita, Kenji Sugita, Hiroshi Daimon, Yuji Hamamoto, Ikutaro Hamada, Yoshitada Morikawa, Yoshihiro Kubozono

SCIENTIFIC REPORTS 6 2016年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

From the C 1s and K 2p photoelectron holograms, we directly reconstructed atomic images of the cleaved surface of a bimetal-intercalated graphite superconductor, (Ca, K) C-8, which differed substantially from the expected bulk crystal structure based on x-ray diffraction (XRD) measurements. Graphene atomic images were collected in the in-plane cross sections of the layers 3.3 angstrom and 5.7 angstrom above the photoelectron emitter C atom and the stacking structures were determined as AB-and AA-type, respectively. The intercalant metal atom layer was found between two AA-stacked graphenes. The K atomic image revealing 2 x 2 periodicity, occupying every second centre site of C hexagonal columns, was reconstructed, and the Ca 2p peak intensity in the photoelectron spectra of (Ca, K) C-8 from the cleaved surface was less than a few hundredths of the K 2p peak intensity. These observations indicated that cleavage preferentially occurs at the KC8 layers containing no Ca atoms.

DOI： 10.1038/srep36258

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Superconductivity in (NH3)(y)NaxFeSe0.5Te0.5 査読

Lu Zheng, Yusuke Sakai, Xiao Miao, Saki Nishiyama, Takahiro Terao, Ritsuko Eguchi, Hidenori Goto, Yoshihiro Kubozono

PHYSICAL REVIEW B 94 ( 17 ) 2016年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Na-intercalated FeSe0.5Te0.5 was prepared using the liquid NH3 technique, and a superconducting phase exhibiting a superconducting transition temperature (T-c) as high as 27 K was discovered. This can be called the high-T-c phase since a 21 K superconducting phase was previously obtained in (NH3)(y)NaxFeSe0.5Te0.5. The chemical composition of the high-T-c phase was determined to be (NH3)(0.61(4))Na-0.63(5) Fe0.85Se0.55(3) Te-0.44(2). The x-ray diffraction patterns of both phases show that a larger lattice constant c (i.e., FeSe0.5Te0.5 plane spacing) produces a higher T-c. This behavior is the same as that of metal-doped FeSe, suggesting that improved Fermi-surface nesting produces the higher T-c. The high-T-c phase converted to the low-T-c phase within several days, indicating that it is a metastable phase. The temperature dependence of resistance for both phases was recorded at different magnetic fields, and the critical fields were determined for both phases. Finally, the T-c versus c phase diagram was prepared for the metal-doped FeSe0.5Te0.5, which is similar to that of metal-doped FeSe, although the T-c is lower.

DOI： 10.1103/PhysRevB.94.174505

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Chemical analysis of superconducting phase in K-doped picene 査読

Takashi Kambe, Saki Nishiyama, Huyen L. T. Nguyen, Takahiro Terao, Masanari Izumi, Yusuke Sakai, Lu Zheng, Hidenori Goto, Yugo Itoh, Taiki Onji, Tatsuo C. Kobayashi, Hisako Sugino, Shin Gohda, Hideki Okamoto, Yoshihiro Kubozono

JOURNAL OF PHYSICS-CONDENSED MATTER 28 ( 44 ) 2016年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Potassium-doped picene (K(3.0)picene) with a superconducting transition temperature (TC) as high as 14 K at ambient pressure has been prepared using an annealing technique. The shielding fraction of this sample was 5.4% at 0 GPa. The TC showed a positive pressure-dependence and reached 19 K at 1.13 GPa. The shielding fraction also reached 18.5%. To investigate the chemical composition and the state of the picene skeleton in the superconducting sample, we used energy-dispersive x-ray (EDX) spectroscopy, MALDI-time-of-flight (MALDI-TOF) mass spectroscopy and x-ray diffraction (XRD). Both EDX and MALDI-TOF indicated no contamination with materials other than K-doped picene or K-doped picene fragments, and supported the preservation of the picene skeleton. However, it was also found that a magnetic K-doped picene sample consisted mainly of picene fragments or K-doped picene fragments. Thus, removal of the component contributing the magnetic quality to a superconducting sample should enhance the volume fraction.

DOI： 10.1088/0953-8984/28/44/444001

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Recent progress on carbon-based superconductors 査読

Yoshihiro Kubozono, Ritsuko Eguchi, Hidenori Goto, Shino Hamao, Takashi Kambe, Takahiro Terao, Saki Nishiyama, Lu Zheng, Xiao Miao, Hideki Okamoto

JOURNAL OF PHYSICS-CONDENSED MATTER 28 ( 33 ) 2016年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

This article reviews new superconducting phases of carbon-based materials. During the past decade, new carbon-based superconductors have been extensively developed through the use of intercalation chemistry, electrostatic carrier doping, and surface-proving techniques. The superconducting transition temperature T-c of these materials has been rapidly elevated, and the variety of superconductors has been increased. This review fully introduces graphite, graphene, and hydrocarbon superconductors and future perspectives of high-T-c superconductors based on these materials, including present problems. Carbon-based superconductors show various types of interesting behavior, such as a positive pressure dependence of T-c. At present, experimental information on superconductors is still insufficient, and theoretical treatment is also incomplete. In particular, experimental results are still lacking for graphene and hydrocarbon superconductors. Therefore, it is very important to review experimental results in detail and introduce theoretical approaches, for the sake of advances in condensed matter physics. Furthermore, the recent experimental results on hydrocarbon superconductors obtained by our group are also included in this article. Consequently, this review article may provide a hint to designing new carbon-based superconductors exhibiting higher T-c and interesting physical features.

DOI： 10.1088/0953-8984/28/33/334001

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Emergence of superconductivity in (NH3)(y)MxMoSe2 (M: Li, Na and K) 査読

Xiao Miao, Saki Nishiyama, Lu Zheng, Hidenori Goto, Ritsuko Eguchi, Hiromi Ota, Takashi Kambe, Kensei Terashima, Takayoshi Yokoya, Huyen T. L. Nguyen, Tomoko Kagayama, Naohisa Hirao, Yasuo Ohishi, Hirofumi Ishii, Yen-Fa Liao, Yoshihiro Kubozono

SCIENTIFIC REPORTS 6 2016年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

We report syntheses of new superconducting metal-doped MoSe2 materials (MxMoSe2). The superconducting MxMoSe2 samples were prepared using a liquid NH3 technique, and can be represented as '(NH3)(y)MxMoSe2'. The T(c)s of these materials were approximately 5.0 K, independent of x and the specific metal atom. X-ray diffraction patterns of (NH3)(y)NaxMoSe2 were recorded using polycrystalline powders. An increase in lattice constant c showed that the Na atom was intercalated between MoSe2 layers. The x-independence of c was observed in (NH3)(y)NaxMoSe2, indicating the formation of a stoichiometric compound in the entire x range, which is consistent with the x-independence of T-c. A metallic edge of the Fermi level was observed in the photoemission spectrum at 30 K, demonstrating its metallic character in the normal state. Doping of MoSe2 with Li and K also yielded superconductivity. Thus, MoSe2 is a promising material for designing new superconductors, as are other transition metal dichalcogenides.

DOI： 10.1038/srep29292

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