Dissecting spin-phonon equilibration in ferrimagnetic insulators by ultrafast lattice excitation

Abstract

Ultrafast heating of a ferrimagnet’s crystal lattice leads to a new state of matter with hot spins yet unchanged magnetization.

Laser‐Driven Strong‐Field Terahertz Sources

“…Examples include magnon-magnon interactions, [177] electron-phonon coupling in semiconductors [178,179] and superconductors, [11] and the coupling of collective nuclear modes of solvents such as water. [21,22] An intense THz pump pulse is used to resonantly excite optical phonons. [21,22] An intense THz pump pulse is used to resonantly excite optical phonons.…”

“…[122,180] In particular, to reveal interactions between the crystal lattice and spins in magnetically ordered solids, one can make use of the generic pump-probe scheme shown in Figure 26. [22] By applying this scheme to the rareearth orthoferrite ErFeO 3 , a new coupling channel through anharmonic phonon coupling was discovered. The impact on the spin subsystem is monitored by measuring the transient Faraday effect, potentially over multiple time scales from femtoseconds to milliseconds.…”

“…The impact on the spin subsystem is monitored by measuring the transient Faraday effect, potentially over multiple time scales from femtoseconds to milliseconds. [22] Adv. [21] In the model insulating ferrimagnet YIG, the equilibration of crystal lattice and spins was revealed and shown to proceed on distinctly different time scales as fast as 1 ps (in terms of energy exchange) and as slow as 100 ns (in terms of angular-momentum exchange).…”

“…For example, in solids, the THz range overlaps with the frequency of lattice vibrations (phonons), the collision rates of conduction electrons, the binding energy of bound electron-hole pairs (excitons), and the precession frequency of spin waves (magnons). [17] Remarkable experimental results such as switching of magnetic order, [18,19] parametric amplification of optical phonons, [20] novel insights into spin-lattice coupling, [21,22] and acceleration of free electrons in a THz linear accelerator [23] were achieved only recently. The majority of these studies used relatively weak THz fields and, thus, probed the linear response of the material, without inducing notable material modifications.…”

“…[3][4][5][6][7][8][9][10][11][12][13] Instead of using weak fields to primarily observe selected THz modes such as phonons or magnons, strong fields allow one to actively drive them to unprecedentedly large amplitudes, potentially thereby resulting in novel states of matter. [17] Remarkable experimental results such as switching of magnetic order, [18,19] parametric amplification of optical phonons, [20] novel insights into spin-lattice coupling, [21,22] and acceleration of free electrons in a THz linear accelerator [23] were achieved only recently. [17] Remarkable experimental results such as switching of magnetic order, [18,19] parametric amplification of optical phonons, [20] novel insights into spin-lattice coupling, [21,22] and acceleration of free electrons in a THz linear accelerator [23] were achieved only recently.…”