Basic studies on the small-sized Josephson superlattices for the occurrence of mesoscopic phenomena and for the application to electronic devices

小尺寸约瑟夫森超晶格介观现象发生及其在电子器件中的应用的基础研究

• 批准号: 13450119
• 负责人: OYA Gin-ichiro
• 金额: $ 8.13万
• 依托单位: Utsunomiya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450119/
• 关键词: high-T_c oxide superconductor; (Bi_<1-x>Pb_x)_2Sr_2CaCu_2O_y; intrinsic Josephson junction; Josephson effect; quasiparticle tunneling; d-wave superconductor; Coulomb blockade; subgap structure; 酸化物高温超電導体; トンネル効果; 超伝導量子干渉素子; エネルギーギャップ; 高温超伝導体 /

The purpose of this study is to clarify the essential tunneling properties and further develop the mesoscopic phenomena of small-sized natural superlattices of intrinsic Josephson junctions with lateral dimensions decreased down to submicron in layered high-temperature (high-T_c) oxide superconductor (Bi_<1-x>Pb_x)_2Sr_2CaCu_2O_y (0【less than or equal】x【less than or equal】0.2) single crystals (with transition temperatures T_c of〜85K), which consist of the stacking of superconducting CuO_2 layers of 0.3nm thickness alternating with other semiconducting or insulating layers of 1.2nm thickness, with the Josephson coupling between every adjacent superconducting layers via nonmetallic layers, and also to get information for the application of the superlattices to electronic devices.The obtained results are as follows :1.A fabrication technology of a small-sized rectangular mesa shape of superlattice devices composed of intrinsic Josephson junctions with lateral dimensions decreased down to … More 0.7×0.7μm^2 has been developed for the single crystals.2.Clear superconducting gaps have been successfully observed on the current-voltage characteristics of the small-sized devices. The values of gaps Δ(4.2K) have been found to be 25-30meV, independent of x.3.A theoretical model to explain the overall profile of the quasiparticle tunneling current-voltage characteristics, which shows the superconducting gap, has been established.4.Fine subgap structures have also been observed on the quasiparticle branches of the current-voltage characteristics, independent of x, temperature and weak magnetic field. This has been interpreted to be due to an interaction between Raman-active optical phonons and ac Josephson oscillation in the intrinsic Josephson junction.5.Critical current densities J_c at 4.2K have been observed to decrease controllably with decreasing the lateral dimensions to submicron and increasing the number of junctions in the small-sized devices of Bi_2Sr_2CaCu_2O_y. This may be considered to be due to the Coulomb blockade effect. However, the single Cooper-pair tunneling has not been clearly confirmed for the devices. Less

本研究的目的是阐明高温（高T_c）氧化物超导体（Bi_<1-x>Pb_x）_2Sr_2CaCu_2O_y（0【小于等于】x【小于等于】0.2）单晶（T_c为~ 85K）中固有Josephson结横向尺寸降至亚微米的小尺寸天然超晶格的基本隧穿特性，并进一步发展其介观现象。将厚度为0.3nm的超导CuO_2层与其他厚度为1.2nm的半导体或绝缘层交替堆叠，并通过非金属层在相邻的超导层之间进行约瑟夫森耦合，从而为超晶格在电子器件中的应用提供信息。得到的结果如下：1。本文提出了一种由内禀约瑟夫森结组成的小尺寸矩形台状超晶格器件的制造技术，其横向尺寸减小到…More 0.7×0.7μm^2。在小尺寸器件的电流-电压特性上成功地观察到明显的超导间隙。发现间隙Δ（4.2K）的值为25-30meV，与x.3无关。建立了一个理论模型来解释显示超导间隙的准粒子隧穿电流-电压特性的总体轮廓。在准粒子分支上还观察到精细的亚隙结构，其电流电压特性不受x、温度和弱磁场的影响。这被解释为由于拉曼主动光学声子与内在约瑟夫森结中的交流约瑟夫森振荡之间的相互作用。在小尺寸Bi_2Sr_2CaCu_2O_y器件中，4.2K时的临界电流密度J_c随着横向尺寸减小到亚微米和结数的增加而可控地降低。这可以认为是由于库仑封锁效应。然而，该器件的单库珀对隧道效应尚未得到明确证实。少

项目成果

Saito, Atsushi: "1/f noise of Bi_2Sr_2CaCu_2O_y intrinsic Josephson junctions"J.Appl.Phys.. 90. 2911-2914 (2001)

Saito，Atsushi：“Bi_2Sr_2CaCu_2O_y 固有约瑟夫森结的 1/f 噪声”J.Appl.Phys.. 90. 2911-2914 (2001)

Kitamura, Michihide: "Quaspparticle tunneling current-voltage characteristics of intrinsic Josephson junctions in Bi_2Sr_2CaCu_2O_<8+δ>"Phys.Rev.B. 66. 054519-1-054519-10 (2002)

Kitamura, Michihide：“Bi_2Sr_2CaCu_2O_<8+δ> 中本征约瑟夫森结的四粒子隧道电流-电压特性”Phys.Rev.B. 66. 054519-1-054519-10 (2002)

Oya, Gin-ichiro: "The influence of microwave irradiation on the pronounced subgap structures in intrinsic Josephson junctions of (Bi_<1-x>Pb_x)_2Sr_2CaCu_2O_y"Physica C. 372-376. 110-114 (2002)

Oya，Gin-ichiro：“微波辐射对 (Bi_<1-x>Pb_x)_2Sr_2CaCu_2O_y 固有约瑟夫森结中明显亚间隙结构的影响”Physica C. 372-376。

Au, Nazia Jabeen: "In-phase motion of vortices in intrinsic Josephson junctions in mesas of Bi_2Sr_2CaCu_2O_y single crystals"Trans.Mater.Res.Soc.Jpn.. 29(印刷中). (2004)

Au，Nazia Jabeen：“Bi_2Sr_2CaCu_2O_y 单晶台面中本征约瑟夫森结中涡流的同相运动”Trans.Mater.Res.Soc.Jpn.. 29（出版中）。

Gin-ichiro Oya: "Tunneling phenomena in the intrinsic Josephson junction of high-temperature superconducting Bi_2Sr_2CaCu_2O_<8+δ>"Recent Research Developments in Physics. (発表予定). (2004)

Gin-ichiro Oya：“高温超导 Bi_2Sr_2CaCu_2O_<8+δ> 的本征约瑟夫森结中的隧道现象”物理学的最新研究进展（即将发表）。