Superconductor-Insulator Transition in disordered 2D-Superconductor

无序二维超导中的超导-绝缘体转变

• 批准号: 04452038
• 负责人: NISHIDA Nobuhiko
• 金额: $ 5.25万
• 依托单位: Deot. of Physics, Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452038/
• 关键词: superconductor-insilator transition,; Kosterlitz-Thouless transition,; 2D-superconductors; amorphous superconductors,; superconducting fluctuations; 近接効果; Kostelitz-Thouless転移; 超伝導揺らぎ; Kosterlitz-Thouless転移; グラニュラー超伝導体; Kosteritz-Thouless転移; アモ

In a 2D superconducting system a superconductor-insulator transition occuras at absolute zero as disorderness is increased. We have studied this problem in amorphous Nb ultra-thin films system which are prepared by quecnch-condensation of Nb on a cold Al_2O_3 substarate of liquid helium temperanture. We were able to prepare a-Nb films with thickness from about 3 - 4 * with and the thickness was able to varied in a fine steo of 0.1 *. Furtermore, we have developed a technique to measure electrical resistances of a-Nb thin films in situ in high vacuum and at tempertaures down to 1.6 K.Mean field superconducting transition temperatures (T_<c0>) and Kosterlitz-Thouless transition temperatures (T_<KT>) have been measured with varying film thickness. It has been found that both T_<CO> and T_<KT> decrease with decreasing film thickness, but T_<KT> seems to vanish faster than T_<c0>. This is the first measurement of the dependence of T_<KT> on the thickness of superconducting films. The fast vanishing of T_<KT> means that at absolute zero we have found a new phase where cooper pair exists in the 2D superconducting film, but global phase coherence is absent. This result has been reported in 20 th. Int Conf. on low temperature physics (Eugene, 1993) and reported as a doctor thesis of Atsushi Asamitsu in March of 1994 at Tokyo Institute of Technology. To confirm this result, experiments at temperatures below 1 K are now in progress.

在二维超导系统中，随着位错的增加，在绝对零度处发生超导体-绝缘体转变。我们在液氦温度下的Al_2O_3基片上，用急冷法制备了非晶Nb超薄膜系统，研究了这个问题。我们能够制备厚度为约3 - 4 * 的a-Nb膜，并且厚度能够在0.1 * 的精细范围内变化。此外，我们还发展了一种在高真空和低至1.6K温度下原位测量α-Nb薄膜电阻的技术，测量了不同膜厚下的平均场超导转变温度（T_<c0>）和Kosterlitz-Alzheimer转变温度（T_<KT>）。发现T_1<CO>和T_2<KT>都随膜厚的减小而减小，但<KT>T_1消失得比T_2快<c0>。这是第一次测量T_c<KT>与超导膜厚度的关系。T_0的快速消失<KT>意味着在绝对零度下我们发现了一个新的相，在这个相中，二维超导薄膜中存在库珀对，但不存在全局相相干。这一结果已于20日报道。低温物理国际会议（尤金，1993），并于1994年3月在东京工业大学以Asamitsu的博士论文身份进行了报告。为了证实这一结果，目前正在进行低于1 K的实验。

项目成果

A.Asamitsu, M.Iguchi, A.Ichikawa and N.Nishida: "Disappearance of Superconductivity in Ultra Thin Amorphous Nb films" Physica. 1649. B194-196 (1994)

A.Asamitsu、M.Iguchi、A.Ichikawa 和 N.Nishida：“超薄非晶铌薄膜中超导性的消失”Physica。

A.Asamitsu and N.Nishida: "Disappearance of Superconductivity in Ultra-Thin Amorphous Nb Films" Physica B. (in press). (1994)

A.Asamitsu 和 N.Nishida：“超薄非晶铌薄膜中超导性的消失”Physica B.（出版中）。

A.Asamitsu and N.Nishida: "Disappearance of Superconductivity in Ultra-Thin Amorphous Nb Films" Physica B. 194-196. 1649-1650 (1994)

A.Asamitsu 和 N.Nishida：“超薄非晶铌薄膜中超导性的消失”Physica B. 194-196。

A.Asamitsu: "Disappearance of Superconductivity in Ultra Thin Amorphous Nb Films" Doctor Thesis Tokyo Institute of Technology. (1994)

A.Asamitsu：“超薄非晶铌薄膜中超导性的消失”东京工业大学博士论文。

朝光敦 他3名: "Nb超薄膜の磁場中での絶縁体-超伝導転移II" 日本物理学会年会講演予稿集. 3. (1993)

Atsushi Asamitsu 等 3 人：“磁场中超薄 Nb 薄膜的绝缘体-超导体转变 II”日本物理学会年会论文集 3。（1993 年）。