Dynamics of photo-excited electrons in magnetically ordered TbMnO₃

Directly probing spin dynamics in insulating antiferromagnets using ultrashort terahertz pulses

“…Also, the formation and relaxation of optically excited polarons observed in other manganites and semiconductors typically takes place in < 1 ps [33][34][35] due to the small spatial scales involved. Considering these facts and that a range of different AFM systems all show similar monotonically decreasing spin-lattice thermalization times with temperature [11,13,14,28,36], we suggest that instead of involving excitations associated with a specific type of spin or lattice order (such as polarons), the microscopic mechanism governing spin-lattice relaxation in these compounds could instead more generally be related to the fact that they are all AFMs.…”

“…3 and 4 does not show the initial fast transfer of energy from electrons to phonons that is normally observed in most materials, most likely because of our limited time resolution (∼250 fs). However, optical-pump/opticalprobe measurements on TbMnO 3 , which are directly sensitive to electronic order, show that this process occurs within ∼30-100 fs of photoexcitation [14,28]; this is typical for manganites (see, e.g., [29,30]). Therefore, before the ∼18-25 ps relaxation process described by τ R occurs, the electrons and phonons have already thermalized, pointing towards a phonon-mediated transfer of energy from electrons to spins (also often seen in manganites [31]).…”

Magnetic order dynamics in optically excited multiferroicTbMnO3

“…Pumping either the p d charge transfer band [23] or the d-d transition peak [24] and probing via reflectivity reveals a sharp, time-resolution limited step observed only when the probe polarization was oriented along certain sample directions [24]. This fast step-like response is followed by a two-step relaxation process.…”

Spin-dependent polaron formation dynamics inEu0.75Y0.25MnO3probed by femtosecond pump-probe spectroscopy

“…They interpret it as the loss of kinetic energy by the photoexcited electron via the emission of spin waves (or magnon assisted hopping of the electron). The rise time of ∆R/R is then the amount of time it takes the photoinjected electron to stop hopping from site to site 26 . In our view, this picture does not account for the electron-phonon coupling that leads to the trapping of the polaron that we discussed earlier.…”