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

研究了含时塞曼场作用下Rashba系统的驰豫动力学。我们系的研究人员的实验结果表明，在显示出强烈的拉什巴自旋-轨道耦合的各种系统中，在亚开尔文温度下存在超慢磁阻动力学。这些动态显示出一条惊人的磁阻曲线，该曲线根据磁场扫描的方向和速度遵循不同的轨迹。这种新的效应不能用磁化或磁热效应来解释。我们认为，这种动力学是由于两个Rashba带的费米能级的失谐以及它们的弛豫到平衡的缓慢过程，这是由于传统系统中预期的带间散射机制的抑制。令人惊讶的是，这种非平衡态的驰豫时间是10秒，因此比典型的电子驰豫时间高出几个数量级，这使得这种效应引起了人们的兴趣，并与信息处理中的潜在应用相关。我们的理论研究发现，在低温下，由于动量分裂KR和Rashba系统的手征自旋织构的共同作用，带间跃迁受到强烈的抑制。具体地说，我们现在正在分析在热声子动量小于KR的温度下，载流子和声子池之间的动量交换是如何变得无效的，并且由于Rashba带相反的自旋结构，通过载流子间散射的动量转移被减弱。

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.