1999 Fiscal Year Annual Research Report

ボルテックス液体状態の準粒子状態およびそのダイナミクス

Research Project

Project/Area Number	11129204
Research Institution	The University of Tokyo
Principal Investigator	前田京剛東京大学, 大学院・総合文化研究科, 助教授 (70183605)
Co-Investigator(Kenkyū-buntansha)	北野晴久東京大学, 大学院・総合文化研究科, 助手 (00313164)
Keywords	ボルテックス・ダイナミクス / 準粒子 / 電子状態 / 高周波伝導度 / 洗濯板ノイズ / 動的相図 / 粘性係数
Research Abstract	高温超伝導体の混合状態におけるボルテックスおよびボルテックス格子のダイナミクス(前者はボルテックスコアーの電子状態と密接に関連)を,高周波複素インピーダンスおよび雑音測定を主な手段として探るのが,本プロジェクトにおける,我々の目的である。このような背景を踏まえて,今年度は,(1)YBCO系の磁束の粘性係数の測定(2)同一試料を用いた熱伝導度と高周波インピーダンスの比較(3)これまで,局所ホール素子を用いてボルテックス格子のダイナミクスの研究を行ってきたBi_2Sr_2CaCa_2O_y(BSCCO)単結晶において,伝導雑音の測定を行った。これらの研究により,以下の成果が得られた。 (1)YBCO系で,表面インピーダンスの磁場依存性は,従来超伝導体を念頭においた磁束の運動を表現する表式(Coffy-Clem Model)でよく表現されることがわかり,これより,磁束格子の粘性係数ηが求まった。ηは,複数の周波数でほぼ同じ値をしめし,この値より,磁束格子コアーのエネルギー準位間隔ωoとレベルの広がり1/τの比ωoτは約0.3となり,古典的コアーと考えてもよい状況にあることがわかった。BSCCO系においても同様の測定を,様々なキャリヤ濃度の試料について行い,やはりωoτが0.1程度の値を,いずれの試料においても得た。これらのことから,高温超伝導体ボルテックスコアーが古典的であるという描像は,かなり普遍的なものであると考えられる。 (2)熱伝導度に「異常」のある磁場,あるいは,それ以上の磁場でも,高周波表面インピーダンスには特に何の「異常」もなく,また,熱伝導度に異常のある試料とない試料問で,高周波表面インピーダンスに特に差異は見られなかった。従って,熱伝導の「異常」は相転移によるものではないと示唆される。 (3)あらゆる超伝導体で初めて,いわゆる「選択板」ノイズを観測することに成功し,これにより,動的相図におけるmoving Bragg Glass相の存在が明らかになった。

Research Products
(20 results)

All Other

All Publications (20 results)

[Publications] T. Tsuboi: ""Study of dynamical phase of Bi_2Sr_2CaCu_2Oy by local noise measurement";"Physica B, in press..
[Publications] H. Kitano: ""A collective excitation on the slightly hole-doped ladders of Sr_<14>-xCa_xCu_<24>O_<41> in the microwave and millimeter wave regions";"Physica B, in press..
[Publications] T. Hanaguri: ""Effect of first-order vortex phase transition on the electronic states of Bi_2Sr_2CaCu_2Oy";"J. Low Temp. Phys.. 117. 1405-1409 (1999)
[Publications] A. Maeda: ""Site sensitive measurement of local fluctuation of driven vortex density in Bi_2Sr_2CaCu_2Oy";"J. Low Temp. Phys.. 117. 1329-1333 (1999)
[Publications] H. Kitano: ""Study of both intralayer and interlayer electrodynamics of Bi_2Sr_2CaCu_2Oy in the superconducting state";"J. Low Temp. Phys.. 117. 1241-1245 (1999)
[Publications] A. Maeda: ""Dynamics of vortices and quasiparticles in the mixed state of Bi_2Sr_2CaCu_2Oy""Physica C, in press..
[Publications] A. Maeda: ""Field dependence of penetration depth in an electron-doped cuprate superconductor Nd_<2-x>Ce_xCuO_4 with x=0.16";"J. Phys. Soc. Jpn.. 68. 594-598 (1999)
[Publications] T. Hanaguri: ""Reduction of the superfluid density in the vortex-liquid phase of Bi_2Sr_2CaCu_2Oy";"Phys. Rev. Lett.. 82. 1273-1276 (1999)
[Publications] Y. Tsuchiya: ""Interlayer phase correlation of the vortex system around at the coupling transition in Bi_2Sr_2CaCu_2Oy containing columnar defects";"Phys. Rev. B. 59. 11568-11574 (1999)
[Publications] S. Tajima: ""In-plane charge dynamics in La_<1.6-x>Nd_<0.4>Sr_xCuO_4: Absence of charge gap in the spin/charge ordered state";"Euro Phys. Lett.. 47. 715-721 (1999)
[Publications] A. Maeda: ""Ac charge dynamics in the meissner state and the vortex state of Bi_2Sr_2CaCu_2Oy";"in "Proceedings of the 11th International Symposium on Superconductivity (ISS '98). 193-198 (1999)
[Publications] R. Inoue: ""Microwave and millimeter-wave conductivity of Sr_<14>Cu_<24>O_<41>":"in "Proceedings of the 11th International Symposium on Superconductivity (ISS '98). 121-124 (1999)
[Publications] Y. Tsuchiya: ""High-frequency electromagnetic response in the mixed state of Yba_2Cu_3Oy.";"Physica C, in press..
[Publications] Y. Togawa: ""Conduction noise in Bi_2Sr_2CaCu_2Oy";"Physica C, in press..
[Publications] H. Kitano: ""Observation of collective excitation in Sr_<14-x>Ca_xCu_<24>O_<41>";"Physica C, in press..
[Publications] A. Maeda: ""Comparative study of thermal conductivity and surface impedance of Bi_2Sr_2CaCu_2Oy".:"Physica C, in press..
[Publications] Y. Tsuchiya: ""High frequency surface impedance measurement in the mixed state of Bi_2Sr_2CaCu_2Oy";"ISS ''99 Proc., in press..
[Publications] Y. Togawa: ""The conduction noise observed in Bi_2Sr_2CaCu_2Oy single crystal";"ISS ''99 Proc., in press..
[Publications] H. Kitano: ""Study of highly anisotropic conductivity and penetration depth of Bi_2Sr_2CaCu_2Oy by using a cavity perturbation technique";"ISS ''99 Proc., in press..
[Publications] S. Tajima: ""Optical responses of the stripe phase in high-Tc cuprates";"Physica C, in press..

1999 Fiscal Year Annual Research Report

ボルテックス液体状態の準粒子状態およびそのダイナミクス

Principal Investigator

前田 京剛 東京大学, 大学院・総合文化研究科, 助教授 (70183605)

Research Products

[Publications] T. Tsuboi: ""Study of dynamical phase of Bi_2Sr_2CaCu_2Oy by local noise measurement";"Physica B, in press..

[Publications] H. Kitano: ""A collective excitation on the slightly hole-doped ladders of Sr_<14>-xCa_xCu_<24>O_<41> in the microwave and millimeter wave regions";"Physica B, in press..

[Publications] T. Hanaguri: ""Effect of first-order vortex phase transition on the electronic states of Bi_2Sr_2CaCu_2Oy";"J. Low Temp. Phys.. 117. 1405-1409 (1999)

[Publications] A. Maeda: ""Site sensitive measurement of local fluctuation of driven vortex density in Bi_2Sr_2CaCu_2Oy";"J. Low Temp. Phys.. 117. 1329-1333 (1999)

[Publications] H. Kitano: ""Study of both intralayer and interlayer electrodynamics of Bi_2Sr_2CaCu_2Oy in the superconducting state";"J. Low Temp. Phys.. 117. 1241-1245 (1999)

[Publications] A. Maeda: ""Dynamics of vortices and quasiparticles in the mixed state of Bi_2Sr_2CaCu_2Oy""Physica C, in press..

[Publications] A. Maeda: ""Field dependence of penetration depth in an electron-doped cuprate superconductor Nd_<2-x>Ce_xCuO_4 with x=0.16";"J. Phys. Soc. Jpn.. 68. 594-598 (1999)

[Publications] T. Hanaguri: ""Reduction of the superfluid density in the vortex-liquid phase of Bi_2Sr_2CaCu_2Oy";"Phys. Rev. Lett.. 82. 1273-1276 (1999)

[Publications] Y. Tsuchiya: ""Interlayer phase correlation of the vortex system around at the coupling transition in Bi_2Sr_2CaCu_2Oy containing columnar defects";"Phys. Rev. B. 59. 11568-11574 (1999)

[Publications] S. Tajima: ""In-plane charge dynamics in La_<1.6-x>Nd_<0.4>Sr_xCuO_4: Absence of charge gap in the spin/charge ordered state";"Euro Phys. Lett.. 47. 715-721 (1999)

[Publications] A. Maeda: ""Ac charge dynamics in the meissner state and the vortex state of Bi_2Sr_2CaCu_2Oy";"in "Proceedings of the 11th International Symposium on Superconductivity (ISS '98). 193-198 (1999)

[Publications] R. Inoue: ""Microwave and millimeter-wave conductivity of Sr_<14>Cu_<24>O_<41>":"in "Proceedings of the 11th International Symposium on Superconductivity (ISS '98). 121-124 (1999)

[Publications] Y. Tsuchiya: ""High-frequency electromagnetic response in the mixed state of Yba_2Cu_3Oy.";"Physica C, in press..

[Publications] Y. Togawa: ""Conduction noise in Bi_2Sr_2CaCu_2Oy";"Physica C, in press..

[Publications] H. Kitano: ""Observation of collective excitation in Sr_<14-x>Ca_xCu_<24>O_<41>";"Physica C, in press..

[Publications] A. Maeda: ""Comparative study of thermal conductivity and surface impedance of Bi_2Sr_2CaCu_2Oy".:"Physica C, in press..

[Publications] Y. Tsuchiya: ""High frequency surface impedance measurement in the mixed state of Bi_2Sr_2CaCu_2Oy";"ISS ''99 Proc., in press..

[Publications] Y. Togawa: ""The conduction noise observed in Bi_2Sr_2CaCu_2Oy single crystal";"ISS ''99 Proc., in press..

[Publications] H. Kitano: ""Study of highly anisotropic conductivity and penetration depth of Bi_2Sr_2CaCu_2Oy by using a cavity perturbation technique";"ISS ''99 Proc., in press..

[Publications] S. Tajima: ""Optical responses of the stripe phase in high-Tc cuprates";"Physica C, in press..

前田京剛東京大学, 大学院・総合文化研究科, 助教授 (70183605)