研究者詳細 - 笠原　成

論文 - 笠原　成

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鉄系超伝導体BaFe2(As1-xPx)2にみる非フェルミ液体的電子輸送現象と量子臨界点的振る舞い

笠原成

京都大学低温物質科学研究センター誌 ( 17 ) 10 - 18 2010年12月

記述言語：日本語出版者・発行元：低温物質科学研究センター

Non-Fermi liquid like charge transport properties and quantum critical behaviors observed in high-quality single crystals of BaFe[2](As[1-x]Px)[2] are reviewed. Near the SDW end point, charge transport coefficients, including resistivity, Hall coefficient and magnetoresistance, exhibit striking deviations from the conventional Fermi liquid properties. De Haas-van Alphen effect measurements in a wide range of superconducting dome reveal that thevolume of the Fermi surfaces shrink and the effective masses are enhanced as x approaches the critical concentration with highest Tc. It is also shown that antiferromagnetic fluctuations deduced from [31]P-NMR measurements are notably enhanced near this optimal composition, where magnetically ordered temperature θ deduced from relaxation rate is found to vanish. It is likely that these trends originate from the many-body interaction which gives rise to high-temperature superconductivity in iron-pnictides.

DOI： 10.14989/153265

Chemical Pressure and Physical Pressure in BaFe2(As1-xPx)(2) 査読

Lina E. Klintberg, Swee K. Goh, Shigeru Kasahara, Yusuke Nakai, Kenji Ishida, Michael Sutherland, Takasada Shibauchi, Yuji Matsuda, Takahito Terashima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 ( 12 ) 1 - 123706 2010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：PHYSICAL SOC JAPAN

Measurements of the superconducting transition temperature, T-c, under hydrostatic pressure via bulk AC susceptibility were carried out on several concentrations of phosphorous substitution in BaFe2-(As1-xRx)(2). The pressure dependence of unsubstituted BaFe2As2, phosphorous concentration dependence of BaFe2(As1-xPx)(2), as well as the pressure dependence of BaFe2(As1-xPx)(2) all point towards an identical maximum T-c of 31 K. This demonstrates that phosphorous substitution and physical pressure result in similar superconducting phase diagrams, and that phosphorous substitution does not induce substantial impurity scattering.

DOI： 10.1143/JPSJ.79.123706

Quasiparticle Scattering Induced by Charge Doping of Iron-Pnictide Superconductors Probed by Collective Vortex Pinning 査読

Cornelis J. van der Beek, Marcin Konczykowski, Shigeru Kasahara, Takahito Terashima, Ryuji Okazaki, Takasada Shibauchi, Yuji Matsuda

PHYSICAL REVIEW LETTERS 105 ( 26 ) 1 - 267002 2010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 PHYSICAL SOC

Charge doping of iron-pnictide superconductors leads to collective pinning of flux vortices, whereas isovalent doping does not. Moreover, flux pinning in the charge-doped compounds is consistently described by the mean-free path fluctuations introduced by the dopant atoms, allowing for the extraction of the elastic quasiparticle scattering rate. The absence of scattering by dopant atoms in isovalently doped BaFe(2)(As(1-x)P(x))(2) is consistent with the observation of a linear temperature dependence of the low-temperature penetration depth in this material.

DOI： 10.1103/PhysRevLett.105.267002

Superconductivity induced by isovalent doping in single crystals of BaFe2(As1-xPx)(2) 査読

S. Kasahara, K. Hashimoto, R. Okazaki, H. Shishido, M. Yamashita, K. Ikada, S. Tonegawa, N. Nakata, Y. Sensyu, H. Takeya, K. Hirata, T. Shibauchi, T. Terashima, Y. Matsuda

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( SUPPL.1 ) S462 - S463 2010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：ELSEVIER SCIENCE BV

Single crystals of BaFe2(As1-xPx)(2) are successfully grown. Resistivity measurements show a systematic reduction of structural and antiferromagnetic spin-density-wave (SOW) transition temperatures and a subsequent emergence of superconductivity upon P-doping. A dome shaped superconducting phase is shown in a wide range of x, with the highest transition temperature T-c approximate to 31 K locating near the end of SDW phase. A pronounced T-linear resistivity in the normal state is found in the vicinity of the optimally doping, showing a clear distinction from the conventional Fermi-liquid picture. The evolution of the resistivity and the phase diagram resemble those found in the parent BaFe2As2 under pressures, indicating that the substitution of P for As serve as chemical pressures. (c) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2009.10.137

Characterization of FeSe single crystals 査読

Hiroyuki Takeya, Shigeru Kasahara, Kazuto Hirata, Takashi Mochiku, Akira Sato, Yoshihiko Takano

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 S497 - S498 2010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：ELSEVIER SCIENCE BV

Superconductivity at 8 K was reported in beta-FeSe with a tetragonal PbO structure but not in delta-FeSe with a hexagonal NiAs structure. The superconducting transition temperature was then increased up to 37 K (on-set) by high pressure on polycrystalline samples. We report a study of the characterization on single crystals of FeSe superconductors. FeSe single crystals were grown using two methods, simple cooling from stoichiometric melt and flux using NaCl/KCl. While a ball-shaped aggregation composed of thick FeSe crystals was grown from the stoichiometric melt, thin hexagonal-shaped crystals with a size up to 1 mm were grown using the NaCl/KCl flux. The two different crystals indicated superconductivity around at 8 K in spite of their hexagonal shape, suggesting a non-superconducting compound with the NiAs-type hexagonal structure. According to the analyses using an X-ray diffractometer and a scanning electron microscope, the crystals contain microcracks that could be caused by stress. We assume that the hexagonal-shaped crystals grown at high temperature may turn partly to tetragonal beta-FeSe at the beta-delta structure transition temperature. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2009.10.041

Antiferromagnetic fluctuations in iron pnictide superconductor BaFe2(As0.67P0.33)(2) investigated by P-31 NMR 査読

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

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 S420 - S421 2010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：ELSEVIER SCIENCE BV

P-31 NMR was performed on the normal state in the newly discovered iron pnictide superconductor BaFe2(As0.67P0.33)(2) with maximum T-c of 30 K. The Knight shift is temperature-independent while the nuclear spin-lattice relaxation rate divided by temperature (T-1 T)(-1) exhibits a more than twofold increase on cooling. This contrasting behavior clearly indicates the development of low-lying antiferrornagnetic fluctuations in BaFe2(As0.67P0.33)(2) as observed in (Ba1-xKx)Fe2As2. The observed low-lying antiferromagnetic fluctuations may be universal in optimally doped "122" superconductors, in contrast to "1111" superconductors. (c) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.01.047

Unconventional Superconductivity and Antiferromagnetic Quantum Critical Behavior in the Isovalent-Doped BaFe2(As1-xPx)(2) 査読

Y. Nakai, T. Iye, S. Kitagawa, K. Ishida, H. Ikeda, S. Kasahara, H. Shishido, T. Shibauchi, Y. Matsuda, T. Terashima

PHYSICAL REVIEW LETTERS 105 ( 10 ) 107003 - 107003 2010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

Spin dynamics evolution of BaFe2(As1-xPx)(2) was probed as a function of P concentration via P-31 NMR. Our NMR study reveals that two-dimensional antiferromagnetic (AF) fluctuations are notably enhanced with little change in static susceptibility on approaching the AF phase from the superconducting dome. Moreover, the magnetically ordered temperature theta deduced from the relaxation rate vanishes at optimal doping. These results provide clear-cut evidence for a quantum-critical point, suggesting that the AF fluctuations associated with the quantum-critical point play a central role in the high-T-c superconductivity.

DOI： 10.1103/PhysRevLett.105.107003

Anisotropic superconducting properties of optimally doped BaFe2(As0.65P0.35)(2) under pressure 査読

Swee K. Goh, Y. Nakai, K. Ishida, L. E. Klintberg, Y. Ihara, S. Kasahara, T. Shibauchi, Y. Matsuda, T. Terashima

PHYSICAL REVIEW B 82 ( 9 ) 2010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

Magnetic measurements on optimally doped single crystals of BaFe2(As(1-x)Px)(2) (x approximate to 0.35) with magnetic fields applied along different crystallographic axes were performed under pressure, enabling the pressure evolution of coherence lengths and the anisotropy factor to be followed. Despite a decrease in the superconducting critical temperature, our studies reveal that the superconducting properties become more anisotropic under pressure. With appropriate scaling, we directly compare these properties with the values obtained for BaFe2(As1-xPx)(2) as a function of phosphorus content.

DOI： 10.1103/PhysRevB.82.094502

Specific heat versus field in the 30 K superconductor BaFe2(As0.7P0.3)(2) 査読

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

PHYSICAL REVIEW B 81 ( 21 ) 2010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 specific-heat measurements on well characterized single crystals of the Fe-based superconductor BaFe2(As0.7P0.3)(2), from the same batch on which previous penetration depth, NMR, and thermal-conductivity measurements have observed a high density of low-energy excitations, which have been interpreted in terms of order-parameter nodes. Within the resolution of our measurements, the low-temperature limiting C/T is found to be linear in field, i.e., we find no evidence for a Volovik effect associated with nodal quasiparticles in either the clean or dirty limit. We discuss possible reasons for this apparent contradiction, which may be an intrinsic feature of the multiple Fermi-surface sheets present in the iron pnictide superconductors.

DOI： 10.1103/PhysRevB.81.214507

Line nodes in the energy gap of superconducting BaFe2(As1-xPx)(2) single crystals as seen via penetration depth and thermal conductivity 査読

K. Hashimoto, M. Yamashita, S. Kasahara, Y. Senshu, N. Nakata, S. Tonegawa, K. Ikada, A. Serafin, A. Carrington, T. Terashima, H. Ikeda, T. Shibauchi, Y. Matsuda

PHYSICAL REVIEW B 81 ( 22 ) 2010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 magnetic penetration depth and thermal-conductivity data for high-quality single crystals of BaFe2(As1-xPx)(2)(T-c=30 K) which provide strong evidence that this material has line nodes in its energy gap. This is distinctly different from the nodeless gap found for (Ba, K)Fe2As2 which has similar T-c and phase diagram. Our results indicate that repulsive electronic interactions play an essential role for Fe-based high-T-c superconductivity but that uniquely there are distinctly different pairing states, with and without nodes, which have comparable T-c.

DOI： 10.1103/PhysRevB.81.220501

Evolution from Non-Fermi to Fermi Liquid Transport Properties by Isovalent Doping in BaFe2(As1-xPx)2 Superconductors 査読

S. Kasahara, T. Shibauchi, K. Hashimoto, K. Ikada, S. Tonegawa, R. Okazaki, H. Ikeda, H. Takeya, K. Hirata, T. Terashima, Y. Matsuda

Phys. Rev. B 81, 184519, (2010) 81 ( 18 ) 2010年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

The normal-state charge transport is studied systematically in high-quality<br />
single crystals of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ ($0 \leq x \leq 0.71$). By<br />
substituting isovalent P for As, the spin-density-wave (SDW) state is<br />
suppressed and the dome-shaped superconducting phase ($T_c \lesssim 31$ K)<br />
appears. Near the SDW end point ($x\approx0.3$), we observe striking linear<br />
temperature ($T$) dependence of resistivity in a wide $T$-range, and remarkable<br />
low-$T$ enhancement of Hall coefficient magnitude from the carrier number<br />
estimates. We also find that the magnetoresistance apparently violates the<br />
Kohler's rule and is well scaled by the Hall angle $\Theta_H$ as<br />
$\Delta\rho_{xx}/\rho_{xx} \propto \tan^2\Theta_H$. These non-Fermi liquid<br />
transport anomalies cannot be attributed to the simple multiband effects. These<br />
results capture universal features of correlated electron systems in the<br />
presence of strong antiferromagnetic fluctuations.

DOI： 10.1103/PhysRevB.81.184519

Evolution of the Fermi Surface of BaFe2(As1-xPx)(2) on Entering the Superconducting Dome 査読

H. Shishido, A. F. Bangura, A. I. Coldea, S. Tonegawa, K. Hashimoto, S. Kasahara, P. M. C. Rourke, H. Ikeda, T. Terashima, R. Settai, Y. Onuki, D. Vignolles, C. Proust, B. Vignolle, A. McCollam, Y. Matsuda, T. Shibauchi, A. Carrington

PHYSICAL REVIEW LETTERS 104 ( 5 ) 057008 - 57008 2010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

Using the de Haas-van Alphen effect we have measured the evolution of the Fermi surface of BaFe2(As1-xPx)(2) as a function of isoelectric substitution (As/P) for 0.41 < x < 1 (T-c up to 25 K). We find that the volumes of electron and hole Fermi surfaces shrink linearly with decreasing x. This shrinking is accompanied by a strong increase in the quasiparticle effective mass as x is tuned toward the maximum Tc. These results are not explained by simple band structure calculations, and it is likely that these trends originate from the same many-body interactions which give rise to superconductivity.

DOI： 10.1103/PhysRevLett.104.057008

P 31 and A 75 s NMR evidence for a residual density of states at zero energy in superconducting BaFe<inf>2</inf>( As<inf>0.67</inf>P <inf>0.33</inf>)<inf>2</inf> 査読

Nakai, Y., Iye, T., Kitagawa, S., Ishida, K., Kasahara, S., Shibauchi, T., Matsuda, Y., Terashima, T.

Physical Review B - Condensed Matter and Materials Physics 81 ( 2 ) 020503(R)-1 - 020503(R)-4 2010年1月

P-31 and As-75 NMR evidence for a residual density of states at zero energy in superconducting BaFe2(As0.67P0.33)(2) 査読

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

PHYSICAL REVIEW B 81 ( 2 ) 1 - 20503 2010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

P-31 and As-75 NMR measurements were performed in superconducting BaFe2(As0.67P0.33)(2) with T-c = 30 K. The nuclear-spin-lattice relaxation rate T-1(-1) and the Knight shift in the normal state indicate the development of antiferromagnetic fluctuations, and T-1(-1) in the superconducting (SC) state decreases without a coherence peak just below T-c, as observed in (Ba1-xKx)Fe2As2. In contrast to other iron arsenide superconductors, the T-1(-1) proportional to T behavior is observed below 4 K, indicating the presence of a residual density of states at zero energy. Our results suggest that strikingly different SC gaps appear in BaFe2(As1-xPx)(2) despite a comparable T-c value, an analogous phase diagram, and similar Fermi surfaces to (Ba1-xKx)Fe2As2.

DOI： 10.1103/PhysRevB.81.020503

Crystal Growth and Characterization of FeAs-based Superconductors 査読

Hiroyuki Takeya, Shigeru Kasahara, Kazuto Hirata

THERMEC 2009, PTS 1-4 638-642 ( Pt.2 ) 1412 - + 2010年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：TRANS TECH PUBLICATIONS LTD

FeAs-based single crystals of Ba1-xKxFe2As2 and Sr1-xKxFe2As2 were grown in a Mo capsule at the temperatures from 1200 degrees C down to 850 degrees C by a FeAs-self-flux method Most of their sizes were approximately 0.2-0 5 mm. A larger single crystal of Sr Fe2As2 about 7mm in diameter was obtained by the same procedure, as appeared in a round-shape Most of the time, potassium-doped ;crystals tends to be smaller than undoped ones. An example of T-c for a Ba1-xKxFexAs2 single crystal measured with a SQUID magnetometer, which indicates T-c at 38 K. T-c s are sometimes lower dependent on the potassium composition The substitution reaction between Srfe(2)As(2) and potassium was examined. An undoped crystal absorbed potassium at around 600 degrees C and showed superconductivity by the reaction.

DOI： 10.4028/www.scientific.net/MSF.638-642.1412

Rotationally resolved high-resolution spectrum of the S-1-S-0 transition of jet-cooled thioanisole 査読

Hoshino-Nagasaka, Mariko, Suzuki, Tadashi, Ichimura, Teijiro, Kasahara, Shunji, Baba, Masaaki, Kawauchi, Susumu

Physical Chemistry Chemical Physics 12 ( 40 ) 2010年

Microwave Surface-Impedance Measurements of the Magnetic Penetration Depth in Single Crystal Ba1-xKxFe2As2 Superconductors: Evidence for a Disorder-Dependent Superfluid Density 査読

K. Hashimoto, T. Shibauchi, S. Kasahara, K. Ikada, S. Tonegawa, T. Kato, R. Okazaki, C. J. van der Beek, M. Konczykowski, H. Takeya, K. Hirata, T. Terashima, Y. Matsuda

PHYSICAL REVIEW LETTERS 102 ( 20 ) 207001 - 207001 2009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

We report high-sensitivity microwave measurements of the in-plane penetration depth lambda(ab) and quasiparticle scattering rate 1/tau in several single crystals of the hole-doped Fe-based superconductor Ba1-xKxFe2As2 (x approximate to 0.55). While a power-law temperature dependence of lambda(ab) with a power similar to 2 is found in crystals with large 1/tau, we observe an exponential temperature dependence of the superfluid density consistent with the existence of fully opened two gaps in the cleanest crystal we studied. The difference may be a consequence of different levels of disorder inherent in the crystals. We also find a linear relation between the low-temperature scattering rate and the density of quasiparticles, which shows a clear contrast to the case of d-wave cuprate superconductors with nodes in the gap. These results demonstrate intrinsically nodeless order parameters in the Fe arsenides.

DOI： 10.1103/PhysRevLett.102.207001

Specific heat of novel ternary superconductors La3Ni4X4 (X = Si and Ge) 査読

S. Kasahara, H. Fujii, T. Mochiku, H. Takeya, K. Hirata

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 468 ( 15-20 ) 1231 - 1233 2008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：ELSEVIER SCIENCE BV

A new superconductivity in ternary intermetallics of La3Ni4X4, where X = Si and Ge, has been found. The superconducting critical temperatures, TcS, of La3Ni4Si4 and La3Ni4Ge4 defined as the onset of diamagnetism are 1.0 and 0.70 K, respectively. These superconductors have U3Ni4Si4-type crystal structure, with a combination of BaAl4-(ThCr2Si2-) and AlB2-type alternating layers. In this work, we present studies on low temperature specific heat in these nickel compounds to shed light on the superconducting natures. The Sommerfeld coefficient, gamma(n) for both compounds showed relatively high values: gamma(n) = 37.4 mJ/mol K-2 and 36.9 mJ/mol K-2 are derived for La3Ni4Si4 and La3Ni4Ge4, respectively. The Debye temperature Theta(D) in La3Ni4Si4 is estimated as 321 K, while that in La3Ni4Ge4 is given as 284 K. As well as the electron-phonon coupling constant, the electronic density of states at the Fermi level is estimated. It turned out that these materials have high density of states, which is in common to the analogous of La3Pd4Ge4. A new superconductivity in the compounds with U3Ni4Si4-type structure is discussed based on the thermodynamic properties. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2008.05.267

Low temperature specific heat of superconducting ternary intermetallics La(3)Pd(4)Ge(4), La(3)Ni(4)Si(4), and La(3)Ni(4)Ge(4) with U(3)Ni(4)Si(4)-type structure 査読

S. Kasahara, H. Fujii, H. Takeya, T. Mochiku, A. D. Thakur, K. Hirata

JOURNAL OF PHYSICS-CONDENSED MATTER 20 ( 38 ) 2008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：IOP PUBLISHING LTD

A systematic investigation on the thermodynamic properties of La-based ternary intermetallic superconductors crystallizing in a U(3)Ni(4)Si(4)-type structure is presented. The U(3)Ni(4)Si(4)-type structure consists of a characteristic intergrowth of periodic BaAl(4) (ThCr(2)Si(2))- and AlB(2)-type segments. Pristine low temperature specific heat data for recently discovered members La(3)Ni(4)Si(4) and La(3)Ni(4)Ge(4) with T(c)s of 1.0 and 0.7 K, respectively, are presented as well as La(3)Pd(4)Ge(4) with the highest T(c) of 2.5 K in the U(3)Ni(4)Si(4)-type group. Owing to the higher Tcs of U(3)Ni(4)Si(4)-type superconductors than the related ThCr(2)Si(2)-type compounds, comparisons are drawn in our investigations of the ternary intermetallics of LaPd(2)Ge(2), LaNi(2)Si(2), and LaNi(2)Ge(2) having a ThCr(2)Si(2)-type structure. Our investigations of the thermodynamic properties show that La(3)Ni(4)Si(4) and La(3)Ni(4)Ge(4) have higher values gamma(n), N(E(F)), and Theta(D) than La(3)Pd(4)Ge(4). The same trend was found in ThCr(2)Si(2)-type compounds of LaPd(2)Ge(2), LaNi(2)Si(2), and LaNi(2)Ge(2). It turns out that the difference in Tc between La(3)Pd(4)Ge(4), La(3)Ni(4)Si(4), and La(3)Ni(4)Ge(4), as well as the relatively higher Tc of the U(3)Ni(4)Si(4)-type superconductors than of the related ThCr(2)Si(2)-type compounds, are largely due to the strength of electron-phonon coupling.

DOI： 10.1088/0953-8984/20/38/385204

Low temperature specific heat of ternary germanide superconductor La3Pd4Ge4 査読

Shigeru Kasahara, Hiroki Fujil, Takashi Mochiku, Hiroyuki Takeya, Kazuto Hirata

PHYSICA B-CONDENSED MATTER 403 ( 5-9 ) 1119 - 1121 2008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：ELSEVIER SCIENCE BV

Low temperature specific heat measurements are performed in a novel ternary superconductor La3Pd4Ge4, which forms U3Ni4Si4-type crystal structure consisting of the combination of alternating units of AlB2- and BaAl4 (ThCr2Si2)-type layers. The Sommerfeld coefficient gamma(n) = 27.0mJ/molK(2) and the Debye temperature Theta(D) = 256K are derived from the normal state specific heat. The electron-phonon coupling constant and the electronic density of states at the Fermi level are also derived. Temperature dependence of the superconducting electronic specific heat is well described by the BCS exponential behavior with gap Delta(0) = 0.30meV. The results suggest La3Pd4Ge4 has fully opened isotropic gap in the superconducting state. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2007.10.347

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