论文标题
对BKT转变的量子几何贡献：超出平均场理论
Quantum Geometric Contributions to the BKT Transition: Beyond Mean Field Theory
论文作者
论文摘要
我们研究对Berezinskii-Kosterlitz-thouless（BKT）过渡温度的量子几何贡献，$ t _ {\ mathrm {bkt}} $，在BCS理论之外的波动存在下。由于量子几何效应在更强的配对吸引力中变得越来越重要，因此对2D多轨超导性的完全理解需要掺入预制的对。我们发现，通过这些对的有效质量，量子几何形状进入了理论，这表明量子几何效应也存在于非驱动伪随相位阶段中。增加这些几何贡献倾向于提高$ t _ {\ mathrm {bkt}} $，然后以通常压低它的波动效应竞争。我们认为，从配对开始温度$ t^*$与$ t _ {\ mathrm {bkt}} $的比率方面，实际上量化了这些几何项的幅度的方法。我们的论文引起了一项实验研究的关注，该研究表明了温度以及当前如何访问其比率。它们可以从通常用于建立BKT物理的相同电压测量值中提取。我们使用这些观察结果来提供对魔术角扭曲双层石墨烯的几何贡献大小的粗略初步估计。
We study quantum geometric contributions to the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature, $T_{\mathrm{BKT}}$, in the presence of fluctuations beyond BCS theory. Because quantum geometric effects become progressively more important with stronger pairing attraction, a full understanding of 2D multi-orbital superconductivity requires the incorporation of preformed pairs. We find it is through the effective mass of these pairs that quantum geometry enters the theory and this suggests that the quantum geometric effects are present in the non-superconducting pseudogap phase as well. Increasing these geometric contributions tends to raise $T_{\mathrm{BKT}}$ which then competes with fluctuation effects that generally depress it. We argue that a way to physically quantify the magnitude of these geometric terms is in terms of the ratio of the pairing onset temperature $T^*$ to $T_{\mathrm{BKT}}$. Our paper calls attention to an experimental study demonstrating how both temperatures and, thus, their ratio may be currently accessible. They can be extracted from the same voltage-current measurements which are generally used to establish BKT physics. We use these observations to provide rough preliminary estimates of the magnitude of the geometric contributions in, for example, magic angle twisted bilayer graphene.
