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Study of the surface bound state of superfluid 3He-B by a new acrostic technique

利用新的离合技术研究超流体 3He-B 的表面束缚态

基本信息

批准号：
14340102
负责人：
OKUDA Yuichi
金额：
$ 9.09万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340102/
关键词：
Superfluid 3He-B P-wave super fluid surface bound state surface elastic wave transverse acoustic impedance pair breaking order parameter collective mode 粘弾性体超流動3He-B P-波超流動表面束縛状態表面弾性波横波音響インピーダンス対破壊オーダーパラメーター集団励起フェルミ液体

项目摘要

3He sets into the P-wave spin-triplet super fluid phase at around 1 mK. Order parameter of the super fluid has a lot of internal degrees of freedom and hence it can have many superfluid phases. Unfortunately, however, there are only two phases realized ; BW-state(B-phase) and ABM-state(A-phase). Superfluid 3He-B is very sensitive against the solid wall. The perpendicular component of the wave function of with respect to the wall, which is denoted as Δ_〓(k), has a property of odd function near the wall. That is, Δ_〓(-k)=-Δ_〓(k). Due to this property, Δ_〓(k) gradually recovers to the bulk value as the distance from the wall increases with the characteristic length of several times of the coherence length ξ, whereasΔ_// exhibits no effect of the wall. ξ is typically several nanometers. As a result of this spatial variation of Δ_〓(k), there comes out the surface state inside the gap at the wall position. This surface state is called as "Andreev surface bound state", which is a typical feature of P-wave superfluid at the boundary. The property of the surface bound state crucially depends on the boundary condition at the wall. If the reflection of quasi-particles at the wall is diffusive(which is often the case with the ordinary wall), the bound state is not δ-function like, but has wider energy width. These surface properties of superfluid 3He-B is, of course, predicted by the theory, has not been studied experimentally yet. The reason is that we had no relevant probing techniques. In the present project, we succeeded in detecting this surface bound state, by the precise measurement of the acoustic shear motion of AC-cut quarts transducer with proper resonance frequencies. The signature of the surface bound state was detected as a kink of in the real part of the impedance and in the cusp of the imaginary part of it. The experimental result is well reproduced by the numerical calculation of the shear impedance by the Green function model.

3在1mK左右，他进入P波自旋三重态超流体相。超流体的有序参数具有很大的内部自由度，因此可以有许多超流体相。然而，遗憾的是，只实现了两个阶段：BW状态(B阶段)和ABM状态(A阶段)。超流体3He-B对固体壁非常敏感。波函数相对于壁面的垂直分量，记为Δ_〓(K)，在壁面附近具有奇函数性质。也就是说，Δ_〓(-k)=-Δ_〓(K)。由于这一特性，Δ_〓(K)随着与壁的距离的增加而逐渐恢复到体积值，特征长度为相干长度ξ的几倍，而Δ_//不表现出壁的影响。ξ通常是几个纳米。由于Δ_〓(K)的这种空间变化，在壁处的缝隙内出现了表面态。这种表面态被称为“Andreev表面束缚态”，这是P波超流体在边界上的一个典型特征。表面束缚态的性质主要取决于壁面上的边界条件。如果准粒子在壁面上的反射是扩散的(这通常是普通壁面的情况)，则束缚态不是δ函数，而是具有更宽的能量宽度。当然，超流3He-B的这些表面性质是由理论预测的，目前还没有实验研究。原因是我们没有相关的探测技术。在本项目中，我们通过精确测量具有合适共振频率的交流切割石英换能器的声学剪切运动，成功地检测到了这种表面束缚状态。表面束缚态的特征被检测为阻抗的实部和虚部的尖端的扭结。用格林函数模型对剪切阻抗进行了数值计算，实验结果与实验结果吻合较好。