Research of Quantum tunneling phenomena in mesoscopic Josephson superlattice

介观约瑟夫森超晶格量子隧道现象研究

基本信息

批准号：
16360147
负责人：
IRIE Akinobu
金额：
$ 9.66万
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：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360147/
关键词：
high Te superconductor intrinsic Josephson junctions mesoscopic phenomena vortex flow SQUID magnet superconductor structure spin injection Bi_2Sr_2CaCu_2O_y vortex flow 超伝導ギャップ超伝導体接合サブミクロン帯電効果熱活性モデル

项目摘要

We studied quantum tunneling phenomena in intrinsic Josephson superlattice of (Bil-xPbx)_2Sr_2CaCu_2O_y single crystals. In this study, we obtained the following results.1. We developed the new fabricated process to make a stack of small intrinsic Josephson junctions. By using this process, samples with lateral dimensions ranging from sub-μm^2 to several tens μm^2 were successfully fabricated.2. The current-voltage characteristics of BPSCCO intrinsic Josephson junctions showed clear multiple branches with high hysteresis and a well-defined gap structure without negative resistance. The quasiparticle I-V characteristics were in agreement with the feature of a weighted, momentum-averaged d-wave model.3. At intermediate temperature the switching mechanism from zero voltage state to a finite voltage state is due to thermal activation process. At lower temperature switching current distribution became wider due to the influence of multiple switching modes.4. To analyze the vortex dynamics, the inductive coupling model taking into account thermal fluctuations was proposed. The model reproduced the previous experimental results and suggests that the out-of-phase flow of vortices is stable rather than the in-phase flow, and the oscillations of the vortex flow resistance are not directly related to the structure of the vortex lattice.5. The dc SQUIDs with in-plane loop geometry and two stacks of intrinsic Josephson junctions were successfully fabricated using the developed process. The fabricated SQUID showed clear periodic and symmetric flux-voltage characteristics due to the quantum interference between the stacks.6. The hybrid Fe/BSCCO structure was fabricated. After an application of a magnetic field, the suppression of the critical current of intrinsic Josephson junctions due to the spin injection was observed.

我们研究了(Bil-xPbx)_2Sr_2CaCu_2O_y单晶的本征约瑟夫森超晶格中的量子隧道现象，我们得到了以下结果： 1．成功制备了横向尺寸从亚μm^2到几十μm^2的样品。2．BPSCCO本征约瑟夫森电流电压特性。结显示出明显的多分支，具有高滞后和明确的间隙结构，无负电阻。准粒子 I-V 特性与加权动量平均 d 波模型的特征一致。 3．零电压状态到有限电压状态是由于热激活过程，在较低温度下，由于多种开关模式的影响，开关电流分布变得更宽。4．该模型再现了先前的实验结果，表明涡流的异相流比同相流是稳定的，并且涡流阻力的振荡与涡流晶格的结构没有直接关系。 .5. 使用所开发的工艺成功制造了具有面内环路几何形状和两层本征约瑟夫森结的直流 SQUID。由于堆叠之间的量子干涉而产生的通量-电压特性。6．在施加磁场后，观察到由于自旋注入而抑制了本征约瑟夫森结的临界电流。