The effects of thermal and correlated noise on magnons in a quantum ferromagnet. (18th September 2018)

• Record Type: Journal Article
• Authors: Jeske, Jan; Rivas, Ángel; Ahmed, Muhammad H; Martin-Delgado, Miguel A; Cole, Jared H
• Is Part Of: New journal of physics. Volume 20:Number 9(2018:Sep.)
• Publication Date: 2018-09-18
• Subjects: quantum noise -- quantum ferromagnet -- magnons -- spin wave -- master equations; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aadecf
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: The dynamics and thermal equilibrium of spin waves (magnons) in a quantum ferromagnet as well as the macroscopic magnetisation are investigated. Thermal noise due to an interaction with lattice phonons and the effects of spatial correlations in the noise are considered. We first present a Markovian master equation approach with analytical solutions for any homogeneous spatial correlation function of the noise. We find that spatially correlated noise increases the decay rate of magnons with low wave vectors to their thermal equilibrium, which also leads to a faster decay of the ferromagnet's magnetisation to its steady-state value. For long correlation lengths and higher temperature we find that additionally there is a component of the magnetisation which decays very slowly, due to a reduced decay rate of fast magnons. This effect could be useful for fast and noise-protected quantum or classical information transfer and magnonics. We further compare ferromagnetic and antiferromagnetic behaviour in noisy environments and find qualitatively similar behaviour in Ohmic but fundamentally different behaviour in super-Ohmic environments.