Harmonic generation predominantly from a single spin channel in a half metal

Abstract

Harmonic generation in atoms and molecules has reshaped our understanding of ultrafast phenomena beyond the traditional nonlinear optics and has launched attosecond physics. Harmonics from solids represent a new frontier, where both majority and minority spin channels contribute to harmonics.} This is true even in a ferromagnet whose electronic states are equally available to optical excitation. Here, we demonstrate that harmonics can be generated {mostly} from a single spin channel in half metallic chromium dioxide. {An energy gap in the minority channel greatly reduces the harmonic generation}, so harmonics predominantly emit from the majority channel, with a small contribution from the minority channel. However, this is only possible when the incident photon energy is well below the energy gap in the minority channel, so all the transitions in the minority channel are virtual. The onset of the photon energy is determined by the transition energy between the dipole-allowed transition between the O-$2p$ and Cr-$3d$ states. Harmonics {mainly} from a single spin channel can be detected, regardless of laser field strength, as far as the photon energy is below the minority band energy gap. This prediction should be tested experimentally.

arXiv comment18 pages and four figures, Accepted to Physical Review B

References in corpus (11)

• Symmetries and selection rules in Floquet systems: application to harmonic generation in nonlinear optics
• Ultrafast modification of Hubbard $U$ in a strongly correlated material: ab initio high-harmonic generation in NiO
• Transport, optical and electronic properties of the half metal CrO2
• Strong-field physics in three-dimensional topological insulators
• Generating high-order optical and spin harmonics from ferromagnetic monolayers
• Laser induced THz emission from femtosecond photocurrents in Co/ZnO/Pt and Co/Cu/Pt multilayers
• High-harmonic generation in quantum spin systems
• High-harmonic generation in spin-orbit coupled systems
• Ultrafast reduction of exchange splitting in ferromagnetic nickel
• High-order harmonic generation in solid ${\mathbf{C}}_{60}$
• Magic high-order harmonics from a quasi-one-dimensional hexagonal solid