Unusual vortex dynamics in the quantum-liquid phase of superconductors

超导体量子液相中不寻常的涡旋动力学

基本信息

批准号：
18340099
负责人：
OKUMA Satoshi
金额：
$ 10.12万
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：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

How do quantum fluctuations affect the vortex dynamics in type-II superconductors? How do driven vortices flow in the quantum-vortex-liquid (QVL) phase? These are very interesting questions, because they may be closely related to superfluidity (quantum liquid) of^4He and macroscopic quantum tunneling of vortices. However, these questions have not yet been answered experimentally or theoretically. In this work, we study the change in vortex dynamics associated with the change in static vortex states from the thermal to quantum liquid by measuring voltage noise generated by vortex flow. We have prepared amorphous (a)-Mo_xSi_<1-x> and a-Mg_xB_<1-x> films with moderately strong pinning to examine a material dependence. We have also studied a-MoxGe_<1-x> films with weaker pinning to clarify possible effects of pinning on the equilibrium vortex states and vortex dynamics.We find that the vortex liquid states for these amorphous films are similar to each other, involving the QVL phase at low temperature T. We commonly detect the unusual noisy vortex flow in the QVL phase for these films. These results indicate that the presence of the QVL phase and unusual vortex dynamics in QVL are universal, independent of the pinning strength as well as the material of amorphous films. We propose based on noise spectra that the origin of noisy flow is due to vortex bundles that are depinned and pinned randomly, dominated by quantum tunneling, in the stationary flow of QVL.We also study the vortex dynamics in the solid phase of a-Mo_xGe_<1-x> films by using a mode-locking resonance. Dynamic ordering of driven vortex matter is observed down to the lowest T (=0.1 K) measured. We find that at low T, the dynamic melting field is significantly suppressed compared to the static melting field B_c, indicative of quantum-fluctuation induced melting of moving crystals or intrinsic (pin-free) quantum-driven melting of vortex lattice, which occurs below B_c.

量子波动如何影响II型超导体中的涡流动力学？量子涡流（QVL）相中的驱动涡流如何流动？这些是非常有趣的问题，因为它们可能与涡旋的^4HE和宏观量子隧道的超流体（量子液体）密切相关。但是，这些问题尚未在实验或理论上得到回答。在这项工作中，我们研究了通过测量由涡流流产生的电压噪声，与静态涡流状态从热液的变化相关的涡流动力学变化。我们已经准备了无定形（A）-MO_XSI_ <1-X>和A-MG_XB_ <1-X>胶片中适中固定的胶片以检查材料依赖性。 We have also studied a-MoxGe_<1-x> films with weaker pinning to clarify possible effects of pinning on the equilibrium vortex states and vortex dynamics.We find that the vortex liquid states for these amorphous films are similar to each other, involving the QVL phase at low temperature T. We commonly detect the unusual noisy vortex flow in the QVL phase for these films.这些结果表明，QVL中QVL相和异常涡流动力学的存在是通用的，与固定强度以及无定形膜的材料无关。我们基于噪声谱提出，噪声流的起源是由于QVL的固定流动中的涡旋束被扣除和固定为量子，以量子隧道为主。观察到驱动涡流物质的动态排序，以至于测得的最低t（= 0.1 K）。我们发现，与静态熔融场B_C相比，在低t下，动态熔融场受到了显着抑制，这表明量子裂开诱导运动晶体的熔化或固有（无PIN）量子驱动的涡旋晶状体熔化，而涡旋晶状体的熔融在B_C以下出现。

项目成果

期刊论文数量（0）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Vortex Phase Diagram and Dynamics near T=0 in the Liquid Phase of a Thick α-Mo_xGe_<1-x> Film

α-Mo_xGe_<1-x> 厚膜液相中 T=0 附近的涡旋相图和动力学

DOI：
发表时间：
2007
期刊：
Int. J. Mod. Phys. B 21
影响因子：
0
作者：
M. Izaki;H. Shishido;T. Kato;T. Shibauchi;Y. Matsuda and T. Terashima;S. Okuma;S. Okuma
通讯作者：
S. Okuma

Vortex Phase Diagram and Vortex Dynamics at Low Temperature in a Thick a-MegB1-x film

a-MegB1-x 厚膜中低温下的涡旋相图和涡旋动力学