Eley S, Khilstrom K, Fotovat R, Xiao Z L, Chen A, Chen D, Leroux M, Welp U, Kwok W K, Civale L
Condensed Matter and Magnet Science, MPA, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
Department of Physics, Colorado School of Mines, Golden, CO, 80401, USA.
Sci Rep. 2018 Sep 3;8(1):13162. doi: 10.1038/s41598-018-31203-0.
Fascination with glassy states has persisted since Fisher introduced the vortex-glass as a new thermodynamic phase that is a true superconductor that lacks conventional long-range order. Though Fisher's original model considered point disorder, it was later predicted that columnar defects (CDs) could also induce glassiness - specifically, a Bose-glass phase. In YBaCuO (YBCO), glassy states can cause distinct behavior in the temperature (T ) dependent rate of thermally activated vortex motion (S). The vortex-glass state produces a plateau in S(T ) whereas a Bose-glass can transition into a state hosting vortex excitations called double-kinks that can expand, creating a large peak in S(T ). Although glass phases have been well-studied in YBCO, few studies exist of other materials containing CDs that could contribute to distinguishing universal behavior. Here, we report on the effectiveness of CDs tilted ~30° from the c-axis in reducing S in a NbSe crystal. The magnetization is 5 times higher and S is minimized when the field is parallel to the defects versus aligned with the c-axis. We see signatures of glassiness in both field orientations, but do not observe a peak in S(T ) nor a plateau at values observed in YBCO. Finally, we discuss the possibility that competing disorder induces a field-orientation-driven transition from a Bose-glass to an anisotropic glass involving both point and columnar disorder.
自从费舍尔将涡旋玻璃作为一种新的热力学相引入以来，人们一直对玻璃态着迷，这种相是一种真正的超导体，缺乏传统的长程有序。尽管费舍尔的原始模型考虑的是点无序，但后来有人预测柱状缺陷（CDs）也会诱发玻璃态——具体来说，是玻色玻璃相。在钇钡铜氧（YBCO）中，玻璃态会在热激活涡旋运动（S）的温度（T）依赖速率中导致不同的行为。涡旋玻璃态在S（T）中产生一个平台，而玻色玻璃可以转变为一种承载称为双扭结的涡旋激发的状态，双扭结可以扩展，在S（T）中产生一个大的峰值。尽管玻璃相在YBCO中已经得到了充分研究，但对于其他含有可能有助于区分普遍行为的CDs的材料，研究却很少。在这里，我们报告了在NbSe晶体中，与c轴倾斜约30°的CDs在降低S方面的有效性。当磁场平行于缺陷而不是与c轴对齐时，磁化强度高出5倍，且S最小化。我们在两个磁场方向上都看到了玻璃态的特征，但没有观察到S（T）中的峰值，也没有观察到在YBCO中所观察到的值处的平台。最后，我们讨论了竞争无序诱导从玻色玻璃到涉及点无序和柱状无序的各向异性玻璃的场取向驱动转变的可能性。
