论文标题
超导薄膜中涡流动力学和相变的研究
Study of Vortex Dynamics and Phase Transitions in Superconducting Thin Films
论文作者
论文摘要
我的博士学位论文中报道的工作是对II型超导体薄膜涡流动力学和相变的实验研究，该研究使用扫描隧道谱图，低频AC易感性测量和免费运输测量。第一章和第二章涵盖了论文中使用的超导性和方法论的基础。第三章讨论了周期性固定中心对NBN薄膜中涡旋晶格的几何形状和动力学的影响。随之而来的研究描述了涡旋莫特样向涡流金属状态的动态过渡。在第四章中，研究了强障碍对NBN薄膜中涡旋晶格的影响。在这里，我们显示磁场引起的粒度引起的伪gap相，该相可用于解释较强疾病中绝缘体样过渡的超导体。第五章包含对A-Moge薄膜中二维涡旋晶格熔化的研究。在这种情况下，我们讨论了示象涡流液相和BKTHNY两步融化的观察。还描述了样品厚度对这一阶段的影响。在第六章中，我们研究了弱固定的A-Moge薄膜中涡度波动的可能性。还探讨了固定对这种波动的影响以及将量子量化为热交叉的可能性。
The work reported in my doctoral thesis is an experimental study of vortex dynamics and phase transitions in thin films of type II superconductors using scanning tunneling spectroscopy, low frequency ac susceptibility measurements and complimentary transport measurements. Chapter I and II cover basics of superconductivity and methodologies used in the thesis. Chapter III discusses the effect of periodic pinning centers on the geometry and dynamics of vortex lattice in NbN thin films. Consequent study of dynamic transition of vortex Mott-like to vortex metal-like state is described. In Chapter IV, effect of strong disorder on vortex lattice in NbN thin films is studied. Here we show magnetic field induced granularity gives rise to pseudogap phase which is utilized to explain superconductor to insulator-like transition in stronger disorder. Chapter V contains the study of 2-dimensional vortex lattice melting in a-MoGe thin films. We discuss the observation of hexatic vortex fluid phase and the BKTHNY two-step melting in this scenario. Effect of sample thickness on this phases is also described. In Chapter VI, we study the possibility of quantum fluctuation of vortices in weakly pinned a-MoGe thin films. Effect of pinning on this fluctuation and a possibility of a quantum to thermal crossover is also explored.
