研究者詳細 - 笠原　成

論文 - 笠原　成

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Thermodynamic phase diagram, phase competition, and uniaxial pressure effects in BaFe2(As1-xPx)(2) studied by thermal expansion 査読

A. E. Boehmer, P. Burger, F. Hardy, T. Wolf, P. Schweiss, R. Fromknecht, H. von Loehneysen, C. Meingast, H. K. Mak, R. Lortz, S. Kasahara, T. Terashima, T. Shibauchi, Y. Matsuda

PHYSICAL REVIEW B 86 ( 9 ) 2012年9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

High-resolution thermal-expansion and specific-heat data of isovalently substituted single-crystalline BaFe2(As1-xPx)(2) (0 <= x <= 0.33, x = 1) are presented. We show that crystals can be detwinned in situ in the capacitance dilatometer, allowing a study of all three independent crystallographic directions. From the thermal-expansion data, we determine the phase diagram via a thermodynamic probe, study the coupling of the spin-density wave (SDW) and superconducting order parameters, and determine various pressure dependencies of the normal and superconducting states. Our results show that in the underdoped region, superconductivity and SDW order coexist and compete with each other. The resulting phase diagram, however, exhibits a smaller coexistence region of SDW and superconductivity with a steeper rise of T-c on the underdoped side than in, e. g., Ba(Fe1-xCox)(2)As-2. On the overdoped side, where there is no sign of SDW order, the lattice parameters respond to superconductivity in much the same way as to the SDW on the underdoped side, which demonstrates the intimate connection between both kinds of order. Using thermodynamic relations, the uniaxial pressure derivatives of the superconducting critical temperature and the electronic Sommerfeld coefficient are determined from our thermal-expansion data together with the specific-heat data. We find that uniaxial pressure is proportional to P substitution and that the electronic density of states has a maximum at optimal doping. Overall, the coupling of the SDW and superconducting order to the lattice parameters of BaFe2(As1-xPx)(2) is found to be qualitatively very similar to that of the well-studied, supposedly electron-doped Ba(Fe1-xCox)(2)As-2 system.

DOI： 10.1103/PhysRevB.86.094521

Infrared Measurement of the Pseudogap of P-Doped and Co-Doped High-Temperature BaFe2As2 Superconductors 査読

S. J. Moon, A. A. Schafgans, S. Kasahara, T. Shibauchi, T. Terashima, Y. Matsuda, M. A. Tanatar, R. Prozorov, A. Thaler, P. C. Canfield, A. S. Sefat, D. Mandrus, D. N. Basov

PHYSICAL REVIEW LETTERS 109 ( 2 ) 2012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 report on infrared studies of charge dynamics in a prototypical pnictide system: the BaFe2As2 family. Our experiments have identified hallmarks of the pseudogap state in the BaFe2As2 system that mirror the spectroscopic manifestations of the pseudogap in the cuprates. The magnitude of the infrared pseudogap is in accord with that of the spin-density-wave gap of the parent compound. By monitoring the superconducting gap of both P- and Co-doped compounds, we find that the infrared pseudogap is unrelated to superconductivity. The appearance of the pseudogap is found to correlate with the evolution of the antiferromagnetic fluctuations associated with the spin-density-wave instability. The strong-coupling analysis of infrared data further reveals the interdependence between the magnetism and the pseudogap in the iron pnictides.

DOI： 10.1103/PhysRevLett.109.027006

Electronic nematicity above the structural and superconducting transition in BaFe2(As1-xPx)(2) 査読

S. Kasahara, H. J. Shi, K. Hashimoto, S. Tonegawa, Y. Mizukami, T. Shibauchi, K. Sugimoto, T. Fukuda, T. Terashima, Andriy H. Nevidomskyy, Y. Matsuda

NATURE 486 ( 7403 ) 382 - 385 2012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：NATURE PUBLISHING GROUP

Electronic nematicity, a unidirectional self-organized state that breaks the rotational symmetry of the underlying lattice(1,2), has been observed in the iron pnictide(3-7) and copper oxide(8-11) high-temperature superconductors. Whether nematicity plays an equally important role in these two systems is highly controversial. In iron pnictides, the nematicity has usually been associated with the tetragonal-to-orthorhombic structural transition at temperature T-s. Although recent experiments(3-7) have provided hints of nematicity, they were performed either in the low-temperature orthorhombic phase(3,5) or in the tetragonal phase under uniaxial strain(4,6,7), both of which break the 90 degrees rotational C-4 symmetry. Therefore, the question remains open whether the nematicity can exist above T-s without an external driving force. Here we report magnetic torque measurements of the isovalent-doping system BaFe2(As1-xPx)(2), showing that the nematicity develops well above T-s and, moreover, persists to the non-magnetic superconducting regime, resulting in a phase diagram similar to the pseudogap phase diagram of the copper oxides(8,12). By combining these results with synchrotron X-ray measurements, we identify two distinct temperatures-one at T*, signifying a true nematic transition, and the other at T-s (<T*), which we show not to be a true phase transition, but rather what we refer to as a 'meta-nematic transition', in analogy to the well-known meta-magnetic transition in the theory of magnetism.

DOI： 10.1038/nature11178

A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)(2) 査読

K. Hashimoto, K. Cho, T. Shibauchi, S. Kasahara, Y. Mizukami, R. Katsumata, Y. Tsuruhara, T. Terashima, H. Ikeda, M. A. Tanatar, H. Kitano, N. Salovich, R. W. Giannetta, P. Walmsley, A. Carrington, R. Prozorov, Y. Matsuda

SCIENCE 336 ( 6088 ) 1554 - 1557 2012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 ASSOC ADVANCEMENT SCIENCE

In a superconductor, the ratio of the carrier density, n, to its effective mass, m*, is a fundamental property directly reflecting the length scale of the superfluid flow, the London penetration depth, lambda(L). In two-dimensional systems, this ratio n/m* (similar to 1/lambda(2)(L)) determines the effective Fermi temperature, T-F. We report a sharp peak in the x-dependence of lambda(L) at zero temperature in clean samples of BaFe2(As1-xPx)(2) at the optimum composition x = 0.30, where the superconducting transition temperature T-c reaches a maximum of 30 kelvin. This structure may arise from quantum fluctuations associated with a quantum critical point. The ratio of T-c/T-F at x = 0.30 is enhanced, implying a possible crossover toward the Bose-Einstein condensate limit driven by quantum criticality.

DOI： 10.1126/science.1219821

Gradual suppression of antiferromagnetism in BaFe2(As1-xPx)(2): Zero-temperature evidence for a quantum critical point 査読

Tetsuya Iye, Yusuke Nakai, Shunsaku Kitagawa, Kenji Ishida, Shigeru Kasahara, Takasada Shibauchi, Yuji Matsuda, Takahito Terashima

PHYSICAL REVIEW B 85 ( 18 ) 2012年5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

Static and dynamic magnetic properties of lightly P-substituted BaFe2(As1-xPx)(2) were systematically investigated by P-31 NMR. The averaged internal magnetic field at the P site in the zero-temperature limit evaluated from the broadening of NMR spectra in the antiferromagnetic (AFM) phase is gradually suppressed toward x similar to 0.35 with increasing x, which provides definitive evidence for the existence of an AFM quantum critical point (QCP) at x similar to 0.35. The location of the AFM QCP is consistent with the previous estimation from temperature dependence of spin dynamics in the normal state, and the superconducting transition temperature T-c takes the maximum around the QCP. Our experiments, revealing a signature of a QCP extending up to room temperature, establish BaFe2(As1-xPx)(2) as one of the most accessible systems for unraveling the nature of quantum criticality and the relationship between AFM quantum criticality and unconventional superconductivity.

DOI： 10.1103/PhysRevB.85.184505

Epitaxial Thin Films of ATiO(3-x)H(x) (A = Ba, Sr, Ca) with Metallic Conductivity 査読

Takeshi Yajima, Atsushi Kitada, Yoji Kobayashi, Tatsunori Sakaguchi, Guillaume. Bouilly, Shigeru Kasahara, Takahito Terashima, Mikio Takano, Hiroshi Kageyama

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 ( 21 ) 8782 - 8785 2012年5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 CHEMICAL SOC

Epitaxial thin films of titanium perovskite oxyhydride ATiO(3-x)H(x) (A = Ba, Sr, Ca) were prepared by CaH2 reduction of epitaxial ATiO(3) thin films deposited on a (LaAlO3)(0.3)(SrAl0.5Ta0.5O3)(0.7) substrate. Secondary ion mass spectroscopy detected a substantial amount and uniform distribution of hydride within the film. SrTiO3/LSAT thin film hydridized at 530 degrees C for 1 day had hydride concentration of 4.0 X 10(21) atoms/cm(3) (i.e., SrTiO2.75H0.25). The electric resistivity of all the ATiO(3-x)H(x) films exhibited metallic (positive) temperature dependence, as opposed to negative as in BaTiO3-xHx powder, revealing that ATiO(3-x)H(x) are intrinsically metallic, with high conductivity of 10(2)-10(4) S/cm. Treatment with D-2 gas results in hydride/deuteride exchange of the films; these films should be valuable in further studies on hydride diffusion kinetics. Combined with the materials' inherent high electronic conductivity, new mixed electron/hydride ion conductors may also be possible.

DOI： 10.1021/ja302465c

Angle-resolved photoemission study on the superconducting iron-pnictides of BaFe2(As, P)(2) with low energy photons 査読

T. Shimojima, F. Sakaguchi, K. Ishizaka, Y. Ishida, W. Malaeb, T. Yoshida, S. Ideta, A. Fujimori, T. Kiss, M. Okawa, T. Togashi, C. -T. Chen, S. Watanabe, Y. Nakashima, A. Ino, H. Anzai, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, S. Kasahara, T. Terashima, T. Shibauchi, Y. Matsuda, M. Nakajima, S. Uchida, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki, A. Chainani, S. Shin

SOLID STATE COMMUNICATIONS 152 ( 8 ) 695 - 700 2012年4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：PERGAMON-ELSEVIER SCIENCE LTD

We investigate the k(z) dispersion in the hole Fermi surfaces (FSs) and the superconducting (SC) gaps of BaFe2(As0.65P0.35)(2) by employing bulk-sensitive angle-resolved photoemission spectroscopy (ARPES) with low energy photons. We find that this material exhibits a comparable magnitude of SC gaps for three-hole FSs at k(z) similar to pi. The comparable magnitude of the SC gap is observed also at k(z) similar to 0. Since each FS sheet has a distinct orbital character, these observations are an indication of the orbital-independent SC gaps in the hole FSs. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ssc.2011.12.032

Microscopic Evidence of Direct Coupling between Magnetic and Superconducting Order Parameters in BaFe2(As1-xPx)(2) 査読

Tetsuya Iye, Yusuke Nakai, Shunsaku Kitagawa, Kenji Ishida, Shigeru Kasahara, Takasada Shibauchi, Yuji Matsuda, Takahito Terashima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 ( 3 ) 2012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：PHYSICAL SOC JAPAN

The coexistence of magnetism and superconductivity in the isovalent-P-substituted BaFe2(As1-xPx)(2) has been investigated microscopically by P-31-NMR measurements. We found that superconducting (SC) transition occurs in a magnetic region with static ordered moments and that the moments are reduced below the SC transition temperature T-c in the samples near the phase boundary of magnetism and superconductivity. Our results indicate that magnetism and superconductivity coexist spatially but compete with each other on the same Fermi surfaces. The coexistence state is qualitatively different from that observed in other unconventional superconductors and gives a strict constraint on the theoretical model for superconductivity in BaFe2(As1-xPx)(2).

DOI： 10.1143/JPSJ.81.033701

Contrasts in electron correlations and inelastic scattering between LiFeP and LiFeAs revealed by charge transport 査読

S. Kasahara, K. Hashimoto, H. Ikeda, T. Terashima, Y. Matsuda, T. Shibauchi

Physical Review B - Condensed Matter and Materials Physics 85 ( 6 ) 2012年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

By using high-quality single crystals, we quantitatively compare the transport properties between LiFeP and LiFeAs superconductors with compensated electron and hole carriers. The low-temperature resistivity follows the Fermi-liquid AT2 dependence with a factor of ∼3 difference in the coefficient A. This highlights weaker electron correlations in LiFeP, which is consistent with its ∼70 times lower upper critical field than that of LiFeAs. Our analysis of the magnetotransport data indicates that in LiFeP, the electron carriers with lighter masses exhibit stronger temperature dependence of inelastic scattering rate than the holes, which is the opposite to the LiFeAs case. This stark difference in the band-dependent inelastic scattering may be relevant to the recently reported contrasting superconducting gap structures in these two superconductors. © 2012 American Physical Society.

DOI： 10.1103/PhysRevB.85.060503

Contrasts in electron correlations and inelastic scattering between LiFeP and LiFeAs revealed by charge transport 査読

S. Kasahara, K. Hashimoto, H. Ikeda, T. Terashima, Y. Matsuda, T. Shibauchi

PHYSICAL REVIEW B 85 ( 6 ) 2012年2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

By using high-quality single crystals, we quantitatively compare the transport properties between LiFeP and LiFeAs superconductors with compensated electron and hole carriers. The low-temperature resistivity follows the Fermi-liquid AT(2) dependence with a factor of similar to 3 difference in the coefficient A. This highlights weaker electron correlations in LiFeP, which is consistent with its similar to 70 times lower upper critical field than that of LiFeAs. Our analysis of the magnetotransport data indicates that in LiFeP, the electron carriers with lighter masses exhibit stronger temperature dependence of inelastic scattering rate than the holes, which is the opposite to the LiFeAs case. This stark difference in the band-dependent inelastic scattering may be relevant to the recently reported contrasting superconducting gap structures in these two superconductors.

DOI： 10.1103/PhysRevB.85.060503

de Haas-van Alphen Study of the Fermi Surfaces of Superconducting LiFeP and LiFeAs 査読

C. Putzke, A. I. Coldea, I. Guillamon, D. Vignolles, A. McCollam, D. LeBoeuf, M. D. Watson, I. I. Mazin, S. Kasahara, T. Terashima, T. Shibauchi, Y. Matsuda, A. Carrington

PHYSICAL REVIEW LETTERS 108 ( 4 ) 1 - 47002 2012年1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 report a de Haas-van Alphen oscillation study of the 111 iron pnictide superconductors LiFeAs with T-c approximate to 18 Kand LiFeP with T-c approximate to 5 K. We find that for both compounds the Fermi surface topology is in good agreement with density functional band-structure calculations and has almost nested electron and hole bands. The effective masses generally showsignificant enhancement, up to similar to 3 for LiFeP and similar to 5 for LiFeAs. However, one hole Fermi surface in LiFeP shows a very small enhancement, as compared with its other sheets. This difference probably results from k-dependent coupling to spin fluctuations and may be the origin of the different nodal and nodeless superconducting gap structures in LiFeP and LiFeAs, respectively.

DOI： 10.1103/PhysRevLett.108.047002

Nodal versus Nodeless Behaviors of the Order Parameters of LiFeP and LiFeAs Superconductors from Magnetic Penetration-Depth Measurements 査読

K. Hashimoto, S. Kasahara, R. Katsumata, Y. Mizukami, M. Yamashita, H. Ikeda, T. Terashima, A. Carrington, Y. Matsuda, T. Shibauchi

PHYSICAL REVIEW LETTERS 108 ( 4 ) 047003 - 47003 2012年1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

High-precision measurements of magnetic penetration depth lambda in clean single crystals of LiFeAs and LiFeP superconductors reveal contrasting behaviors. In LiFeAs the low-temperature lambda(T) shows a flat dependence indicative of a fully gapped state, which is consistent with previous studies. In contrast, LiFeP exhibits a T-linear dependence of superfluid density alpha lambda(-2), indicating a nodal superconducting order parameter. A systematic comparison of quasiparticle excitations in the 1111, 122, and 111 families of iron-pnictide superconductors implies that the nodal state is induced when the pnictogen height from the iron plane decreases below a threshold value of similar to 1.33 angstrom.

DOI： 10.1103/PhysRevLett.108.047003

Volovik effect in a highly anisotropic multiband superconductor: Experiment and theory 査読

Y. Wang, J. S. Kim, G. R. Stewart, P. J. Hirschfeld, S. Graser, S. Kasahara, T. Terashima, Y. Matsuda, T. Shibauchi, I. Vekhter

PHYSICAL REVIEW B 84 ( 18 ) 2011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

We present measurements of the specific heat coefficient gamma (equivalent to C/T) in the low-temperature limit as a function of an applied magnetic field for the Fe-based superconductor BaFe2(As0.7P0.3)(2). We find both a linear regime at higher fields and a limiting square root H behavior at very low fields. The crossover from a Volovik-like root H to a linear field dependence can be understood from a multiband calculation in the quasiclassical approximation assuming gaps with different momentum dependence on the hole-and electronlike Fermi surface sheets.

DOI： 10.1103/PhysRevB.84.184524

Nodal gap structure of superconducting BaFe2(As1-xPx)(2) from angle-resolved thermal conductivity in a magnetic field 査読

M. Yamashita, Y. Senshu, T. Shibauchi, S. Kasahara, K. Hashimoto, D. Watanabe, H. Ikeda, T. Terashima, I. Vekhter, A. B. Vorontsov, Y. Matsuda

PHYSICAL REVIEW B 84 ( 6 ) 2011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：AMER PHYSICAL SOC

The structure of the superconducting order parameter in the iron-pnictide superconductor BaFe2(As0.67P0.33)(2) (T-c = 31 K) with line nodes is studied by the angle-resolved thermal conductivity measurements in a magnetic field rotated within the basal plane. We find that the thermal conductivity displays distinct fourfold oscillations with minima when the field is directed at +/- 45 degrees with respect to the tetragonal a axis. We discuss possible gap structures that can account for the data, and conclude that the observed results are most consistent with the closed nodal loops located at the flat parts of the electron Fermi surface with high Fermi velocity.

DOI： 10.1103/PhysRevB.84.060507

Specific heat discontinuity, ΔC, at Tc in BaFe2(As0.7P0.3)2-consistent with unconventional superconductivity. 査読

Kim JS, Stewart GR, Kasahara S, Shibauchi T, Terashima T, Matsuda Y

Journal of physics. Condensed matter : an Institute of Physics journal 23 ( 22 ) 222201 - 5 2011年6月

Nesting of electron and hole Fermi surfaces in nonsuperconducting BaFe2P2 査読

B. J. Arnold, S. Kasahara, A. I. Coldea, T. Terashima, Y. Matsuda, T. Shibauchi, A. Carrington

PHYSICAL REVIEW B 83 ( 22 ) 2011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

We report detailed measurements of the de Haas-van Alphen ( dHvA) effect in BaFe2P2, which is the end member of the superconducting series, BaFe2(As1-xPx)(2). Using high-purity samples, we are able to observe dHvA oscillations from all the sheets of the Fermi surface and hence build up a detailed picture of its structure. The results show the existence of a highly warped section of hole surface, which may be the origin of the nodal superconducting gap structure in this series. Importantly, we find that even for this nonsuperconducting end member, one of the hole surfaces almost exactly nests with the inner electron surface. This suggests that improved geometric nesting does not drive the increase in pairing strength with decreasing x in this system.

DOI： 10.1103/PhysRevB.83.220504

Orbital-Independent Superconducting Gaps in Iron Pnictides 査読

T. Shimojima, F. Sakaguchi, K. Ishizaka, Y. Ishida, T. Kiss, M. Okawa, T. Togashi, C. -T. Chen, S. Watanabe, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, K. Ohgushi, S. Kasahara, T. Terashima, T. Shibauchi, Y. Matsuda, A. Chainani, S. Shin

SCIENCE 332 ( 6029 ) 564 - 567 2011年4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 ASSOC ADVANCEMENT SCIENCE

The origin of superconductivity in the iron pnictides has been attributed to antiferromagnetic spin ordering that occurs in close combination with a structural transition, but there are also proposals that link superconductivity to orbital ordering. We used bulk-sensitive laser angle-resolved photoemission spectroscopy on BaFe2(As0.65P0.35)(2) and Ba0.6K0.4Fe2As2 to elucidate the role of orbital degrees of freedom on the electron-pairing mechanism. In strong contrast to previous studies, an orbital-independent superconducting gap magnitude was found for the hole Fermi surfaces. Our result is not expected from the superconductivity associated with spin fluctuations and nesting, but it could be better explained invoking magnetism-induced interorbital pairing, orbital fluctuations, or a combination of orbital and spin fluctuations. Regardless of the interpretation, our results impose severe constraints on theories of iron pnictides.

DOI： 10.1126/science.1202150

Highly Reduced Anatase TiO2-delta Thin Films Obtained via Low-Temperature Reduction 査読

Atsushi Kitada, Shigeru Kasahara, Takahito Terashima, Kazuyoshi Yoshimura, Yoji Kobayashi, Hiroshi Kageyama

APPLIED PHYSICS EXPRESS 4 ( 3 ) 1 - 35801 2011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：JAPAN SOC APPLIED PHYSICS

We report the preparation and physical properties of reduced anatase TiO2-delta thin films obtained via a low-temperature (low-T) reduction using CaH2. The oxygen amounts were controlled in a wider range than ever reported. Some highly reduced anatase films showed resistivities as low as 10(-3) Omega cm at room temperature, both in metallic and semiconducting states. The most conducting metallic sample has very high carrier concentration of 1.6 x 10(21) cm(-3), comparable with those of metal-doped anatase films. Moreover, the magnetoresistance of the films changed its sign twice as a function of delta. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/APEX.4.035801

Two-Dimensional and Three-Dimensional Fermi Surfaces of Superconducting BaFe2(As1-xPx)(2) and Their Nesting Properties Revealed by Angle-Resolved Photoemission Spectroscopy 査読

T. Yoshida, I. Nishi, S. Ideta, A. Fujimori, M. Kubota, K. Ono, S. Kasahara, T. Shibauchi, T. Terashima, Y. Matsuda, H. Ikeda, R. Arita

PHYSICAL REVIEW LETTERS 106 ( 11 ) 117001 - 117001 2011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：AMER PHYSICAL SOC

We have studied the three-dimensional shapes of the Fermi surfaces (FSs) of BaFe2(As1-xPx)(2) (x = 0.38), where superconductivity is induced by isovalent P substitution and by angle-resolved photoemission spectroscopy. Moderately strong electron mass enhancement has been identified for both the electron and hole FSs. Among two observed hole FSs, the nearly two-dimensional one shows good nesting with the outer two-dimensional electron FS, but its orbital character is different from the outer electron FS. The three-dimensional hole FS shows poor nesting with the electron FSs. The present results suggest that the three dimensionality and the difference in the orbital character weaken FS nesting while partial nesting among the outer electron FSs of d(xy) character and/or that within the three-dimensional hole FS becomes dominant, which may lead to the nodal superconductivity.

DOI： 10.1103/PhysRevLett.106.117001

Abrupt recovery of Fermi-liquid transport following the collapse of the c axis in CaFe2(As1-xPx)(2) single crystals 査読

S. Kasahara, T. Shibauchi, K. Hashimoto, Y. Nakai, H. Ikeda, T. Terashima, Y. Matsuda

PHYSICAL REVIEW B 83 ( 6 ) 2011年2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

Single crystals of CaFe2(As1-xPx)(2) are found to exhibit the tetragonal (T) to collapsed-tetragonal (cT) transition at T-cT less than or similar to 100 K for x > 0.05. The c-axis shrinks by similar to 9% below T-cT, which substantially diminishes the interband nesting between the hole and electron bands. In sharp contrast to the superconducting T phase of AFe(2)(As1-xPx)(2) (A = Ba, Sr), where the anomalous non-Fermi liquid transport properties are observed, the resistivity, Hall coefficient, and magnetoresistance data in the Ca-based system all indicate that the standard Fermi liquid behaviors are recovered abruptly below T-cT, and the superconductivity disappears completely. The simultaneous disappearance of the superconductivity and the non-Fermi liquid transport enlightens the essential role of interband-associated fluctuations to the superconductivity in Fe pnictides.

DOI： 10.1103/PhysRevB.83.060505

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