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Slowly-decaying chirality states in low-temperature strongly Rashba-coupled systems.

低温强拉什巴耦合系统中缓慢衰减的手性态。

基本信息

批准号：
2138907
负责人：
金额：
--
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-2138907
关键词：
Slowly decaying chirality states low

项目摘要

We study the relaxation dynamics of Rashba systems under a time-dependent Zeeman field. Experimental findings by researchers in our department indicate ultra-slow magnetoresistance dynamics at sub-Kelvin temperatures in various systems that display strong Rashba spin-orbit coupling. These dynamics display a striking magnetoresistance curve that follows different traces depending on direction and speed of a magnetic field sweep. This novel effect cannot be explained by magnetisation or magnetocaloric effects. We suggest that the dynamics arise from detuning of the Fermi levels of the two Rashba bands and the slowness of their relaxation into equilibrium due to the suppression of interband scattering mechanisms that would be expected in conventional systems. Surprisingly, the relaxation timescale of this non-equilibrium state is 10 seconds so exceeds typical electronic relaxation timescales by several orders of magnitude, which makes this effect intriguing to study and relevant for potential applications in information processing. Our theoretical study finds that at low temperature inter-band transitions become strongly suppressed due to the combined effect of the momentum split kR and the chiral spin texture of a Rashba system. Specifically, we are now analysing how momentum exchange between carriers and the phonon bath becomes ineffective at temperatures where the momentum of thermal phonons is less than kR, and that momentum transfer via inter-carrier scattering is diminished due to the opposing spin structure of the Rashba bands.

研究了含时塞曼场作用下Rashba系统的弛豫动力学。我们部门的研究人员的实验结果表明，在各种系统中，在亚开尔文温度下，超慢的磁阻动力学表现出强烈的Rashba自旋轨道耦合。这些动态显示了惊人的磁阻曲线，根据磁场扫描的方向和速度，该曲线遵循不同的轨迹。这种新的效应不能用磁化或磁热效应来解释。我们认为，动力学产生的两个Rashba带的费米能级的失谐和缓慢的松弛到平衡，由于抑制带间散射机制，将在传统的系统中预期。令人惊讶的是，这种非平衡态的弛豫时间尺度是10秒，因此超过了典型的电子弛豫时间尺度几个数量级，这使得这种效应对研究很有吸引力，并且与信息处理中的潜在应用有关。我们的理论研究发现，在低温下，带间跃迁成为强烈的抑制，由于动量分裂kR和手征自旋纹理的Rashba系统的综合作用。具体地说，我们现在正在分析如何在热声子的动量小于kR的温度下，载流子和声子浴之间的动量交换变得无效，并且由于Rashba带的相反自旋结构，通过载流子间散射的动量传递减少。