Crossover between 0.7-anomaly and Kondo effect - theory, transport measurements and all-optical spin detection

vDelft小组最近的理论进展表明（与Y Meir的情景一致），量子点接触（QPC）电导率的0.7-异常与量子点（QD）的近道效应具有相同的微观起源：两者都是由自旋和相互作用的微妙相互作用引起的，这些相互作用导致QPC或QD低电子密度附近的局部自旋磁化率增强。我们建议通过结合三个小组的专业知识对这两种现象之间的关系进行深入研究：(I)理论（vDelft）：研究一维Hubbard模型来描述QPC-QD交叉，我们将我们的功能重正化群计算推广到有限温度和源漏电压；我们也将致力于模拟实际的QPC/QD约束势。（二）输运实验（路德维希）：我们将制作样品并对其进行研究，使用输运光谱对理论预测进行精确的实验测试；完全表征的样品将用于光学自旋检测，（ii）光学自旋检测（Högele）：我们将扩展我们的光学自旋检测技术，使其具有^m空间分辨率，可以在亚开尔文温度下工作，并使用它来测量我们的横向定义量子点和量子点中的局部自旋极化。通过这种独特的方法组合，我们不仅计划最终揭示0.7异常的微观起源，而且还计划建立一种光学自旋检测的新技术，其在自旋电子学领域的潜在影响远远超出了本提案的范围。

Recent theoretical progress from the vDelft group shows (in accord with a scenario due to Y Meir) that the 0.7- anomaly in the conductance of a quantum point contact (QPC) has the same microscopic origin as the Kondo effect for a quantum dot (QD): both arise from a subtle interplay of spin and interaction effects that cause an enhanced local spin susceptibility in the vicinity of low electron density in the QPC or QD. We propose to conduct an in-depth study of the relation between these two phenomena by combining the expertise of three groups: (I) Theory (vDelft): Studying a one-dimensional Hubbard model to describe the QPC-QD crossover, we will generalize our functional renormalization group calculations to finite temperatures and source-drain voltages; we will also aim to model realistically the QPC/QD confinement potentials. (II) Transport experiments (Ludwig): We will fabricate samples and study them, using transport spectroscopy to conduct precise experimental tests of theoretical predictions; thoroughly characterized samples will then be used for optical spin detection, (ill) Optical spin detection (Högele): We will extend our optical spin detection technique with ^m spatial resolution for operation at sub-Kelvin temperatures, and use it to measure local spin polarization in our lateral defined QDs and QPCs. By this unique combination of methods we plan not only to conclusively unravel the microscopic origin of the 0.7-anomaly but also to establish a new technique for optical spin detection whose potential impact in the field of spintronics goes far beyond the scope of the present proposal.