Spin-phonon coupling parameters from maximally localized Wannier functions and first-principles electronic structure: Single-crystal durene

Abstract

Spin-orbit interaction is an important vehicle for spin relaxation. At finite temperature lattice vibrations modulate the spin-orbit interaction and thus generate a mechanism for spin-phonon coupling, which needs to be incorporated in any quantitative analysis of spin transport. Starting from a density functional theory ab initio electronic structure, we calculate spin-phonon matrix elements over the basis of maximally localized Wannier functions. Such coupling terms form an effective Hamiltonian to be used to extract thermodynamic quantities, within a multiscale approach particularly suitable for organic crystals. The symmetry of the various matrix elements are analyzed by using the Γ-point phonon modes of a one-dimensional chain of Pb atoms. Then the method is employed to extract the spin-phonon coupling of solid durene, a high-mobility crystal organic semiconducting. Owing to the small masses of carbon and hydrogen spin-orbit is weak in durene and so is the spin-phonon coupling. Most importantly we demonstrate that the largest contribution to the spin-phonon interaction originates from Holstein-like phonons, namely from internal molecular vibrations.arXiv:1807.04579v1 [cond-mat.mtrl-sci]

Unconventional Spin Relaxation Involving Localized Vibrational Modes in Ho Single-Atom Magnets

“…Motivated by these observations, we surmise that the peculiar magnetic behavior of Ho single atom magnets is influenced by the contribution of local vibrational modes to the spin-phonon coupling [15,40]. The relaxation process is thermally activated and occurs only at low magnetic fields, i.e., when the two spin levels of the lowest doublet are very close in energy.…”

Impurity band magnetism in organic semiconductors

“…Conversely, when the concentration of localized magnetic moments becomes large, spin waves will enable transport of pure spin currents. A quantitative estimate of the impurities required to observe charge and spin transport in real devices is unfortunately not possible from the calculations we have presented here as it would require multiscale simulations with materialspecific parameters obtained from first principles [60][61][62]. This task goes beyond the goal of the paper and we leave it for future studies.…”

Phono-magnetic analogs to opto-magnetic effects

“…As terahertz and mid-infrared sources are becoming widely available [59], we anticipate that future exper-iments will utilize ionic Raman scattering to generate coherent spin-waves. At the same time, recent improvements in ab-initio spin-lattice dynamics [60][61][62][63][64][65] will accelerate the prediction of phono-magnetic effects in a variety of materials. We believe that our analysis provided in this study makes the first step towards utilizing the physics of coherent optical phononics [18,66] in the field of spintronics [4,5].…”

“…Ionic Raman scattering was predicted half a century ago [39][40][41] and has been demonstrated recently for nonlinear phonon interactions [42][43][44]. The approach presented here can be straightforwardly extended for non-Raman mechanisms, such as one-photon and one-phonon [34,[45][46][47][48][49][50][51][52][53][54] as well as twomagnon processes [55,56], which will be the matter of future work. Our results pave the way for future experiments utilizing phono-magnetic effects in the ultrafast control of magnetic order.…”