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

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.