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）电导的0.7异常与量子点（QD）的近藤效应具有相同的微观起源（雅阁）：两者都是由自旋和相互作用效应的微妙相互作用引起的，这种相互作用效应在QPC中的低电子密度附近引起局部自旋磁化率的增强，一日一次我们建议通过结合三个小组的专业知识来深入研究这两种现象之间的关系：（I）理论（vDelft）：研究一维Hubbard模型来描述QPC-QD交叉，我们将把我们的泛函重整化群计算推广到有限温度和源漏电压;我们还将致力于现实地模拟QPC/QD约束势。(II)传输实验（路德维希）：我们将制造样品并对其进行研究，使用传输光谱对理论预测进行精确的实验测试;然后将彻底表征的样品用于光学自旋检测，（iii）光学自旋检测（Högele）：我们将把我们的光学自旋探测技术扩展到μ m的空间分辨率，以便在亚开尔文温度下工作，并用它来测量我们横向定义的量子点和量子光子晶体中的局域自旋极化。通过这种独特的方法组合，我们计划不仅最终解开0.7异常的微观起源，而且还建立了一种新的光学自旋探测技术，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.