Nonlinear magneto-optical response to light carrying orbital angular momentum

Abstract

We predict a non-thermal magneto-optical effect for magnetic insulators subject to intense light carrying orbital angular momentum (OAM). Using a classical approach to second harmonic generation in non-linear media with specific symmetry properties we predict a significant nonlinear contribution to the local magnetic field triggered by light with OAM. The resulting magnetic field originates from the displacement of electrons driven by the electrical field (with amplitude E 0 ) of the spatially inhomogeneous optical pulse, modeled here as a Laguerre-Gaussian beam carrying OAM. In particular, the symmetry properties of the irradiated magnet allow for magnetic field responses which are second-order (∼ E 2 0 ) and fourth-order (∼ E 4 0 ) in electric-field strength and have opposite signs. For sufficiently high laser intensities, terms ∼ E 4 0 dominate and generate magnetic field strengths which can be as large as several Tesla. Moreover, changing the OAM of the laser beam is shown to determine the direction of the total light-induced magnetic field, which is further utilized to study theoretically the non-thermal magnetization dynamics.

Heisenberg representation of nonthermal ultrafast laser excitation of magnetic precessions

“…It avoids problems caused by material heating, which limits a repetition frequency due to a required cooling time and a recording density due to heat diffusion. Therefore, the demonstration of the UIFE, in which magnetic oscillations in canted antiferromagnet DyFeO 3 were induced by circularly polarized ultrashort laser pulses [5], motivated intensive theoretical [6][7][8][9][10][11][12][13][14][15][16][17][18] and experimental [19][20][21][22][23] studies of this process. A significant progress in development of techniques of ultrafast spin control using femtosecond laser pulses based on the UIFE was demonstrated in recent years [22,[24][25][26][27][28][29][30][31][32][33].…”

Tunable Tesla-Scale Magnetic Attosecond Pulses through Ring-Current Gating

“…Up until this stage, our results fully validate previous works on magnetic fields and impulses generated by strong-fielddriven currents in other systems. 30,35,36,[38][39][40]43 However, as the currents are expected to be relatively long-lived, with electronic coherence times on scales of tens of femtoseconds that would only decay as the electron population in the valence orbitals equilibrates as a result of scattering processes, the magnetic field emission extends for several tens of femtoseconds, or longer. In order to generate shorter pulses, other strategies must be employed.…”

“…Alternatively, optical methods based on femtosecond laser pulses have made substantial progress in producing shorter magnetic bursts through laser-induced currents in plasmas, − plasmonic nanostructures, , semiconductors, − molecules, ,,− or atoms . Interestingly, additional control over the magnetic field features can be gained by shaping the spatial structure of the laser beams. ,,− ,, Nevertheless, to our knowledge the perspective of attosecond time scales has only been theoretically foreseen in relation to the attosecond electromagnetic pulses, ,, where the dominance of the electric field overshadows the magnetic component. Therefore, the generation of isolated, strong, ultrashort magnetic fields is highly desirable to advance the control of purely magnetic phenomena, spintronics, chirotronics, − or even HHG. , Indeed, attosecond magnetic pulses would open up new avenues for the study and manipulation of magnetic phenomena on ultrafast time scales by accessing the fastest magnetic, spin, and chiral dynamics. ,,− For instance, magnetic sources reaching the attosecond scale could boost scientific and technological breakthroughs in ultrafast magnetometry, magnetic phase transitions, materials science, plasma physics, topological systems, and high-speed data storage.…”

“…After reproducing the appearance of stationary ring currents with our theoretical approach, we explore their buildup and their connection to magnetic field emission. Differently from previous approaches to obtain the magnetic field based on particle-in-cell codes, , the induced magnetic moment, or generalized Biot-Savart laws like the Jefimenko equation, , we couple TDDFT and the microscopic Maxwell equations via the Riemann–Silberstein representation using the multisystem framework of Octopus . This formalism allows a reformulation of Maxwell’s equations in Schrödinger-like form, resulting in efficient coupled propagation in real-time and real-space of both the TDDFT KS equations and Maxwell’s equations. , …”

Light-Induced Magnetization at the Nanoscale

“…There are theory proposals for petahertz current generation, including the use of structured laser beams [16,17] or plasmonic excitations in metamaterials [18]. Optical rectification [19] or interference of two copropagation beams [20] were studied, as well as intense circularly polarized laser pulses to trigger charge currents [21]. The distinctive feature of our scheme is the all-optical noninvasive (one XUV and one IR photons) generation of nanoscale [Fig.…”