Ultrafast Quantum Relaxation Dynamics of Magnetically Ordered Systems with Spin Crossover in an Excited State under a Su
- PDF / 651,486 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 171 Views
D MATTER
Ultrafast Quantum Relaxation Dynamics of Magnetically Ordered Systems with Spin Crossover in an Excited State under a Sudden Perturbation Yu. S. Orlova, b, *, S. V. Nikolaevb, S. G. Ovchinnikova, b, and A. I. Nesterovc a Kirensky
Institute of Physics, Federal Research Center KSC, Siberian Branch, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036 Russia b Siberian Federal University, Krasnoyarsk, 660041 Russia c Centro Universitario de Ciencias Exactas e Ingenierías (CUCEI), Universidad de Guadalajara, Guadalajara, 44420 Jalisco, Mexico *e-mail: [email protected] Received July 19, 2020; revised July 19, 2020; accepted July 29, 2020
A theoretical model based on the relaxation equation for the density matrix has been proposed to describe the ultrafast time dynamics of magnetically ordered systems with spin crossover in an excited state under a sudden perturbation. Oscillations of the magnetization, the population of the high-spin state, and the generation of local vibrons at a transition of the system from the light-excited Franck–Condon low-spin state to the highspin ground state. DOI: 10.1134/S0021364020160109
1. A new field called ultrafast magnetism has appeared and developed in the last decade in condensed matter physics [1–5]. Intense ultrashort laser pulses can excite spin dynamics in magnetic materials, which is of great fundamental and applied interest. The main experimental method in this field is the pump–probe technique [6, 7]. Depending on the properties of a magnetic medium, the pump pulse results in ultrafast demagnetization or magnetization reversal of a sample or in the excitation of the precession of the magnetization. The exchange interaction can change because of the interaction with light [8]. Systems with spin crossover [9–11], which can exist in a crystal phase and in the form of complexmolecular aperiodic compounds, are among nonstandard systems interesting for the study of ultrafast magnetic switching. In particular, the authors of [12] studied the light induced spin state trapping (LIESST) effect in the Fe(phen)2(NCS)2 compound [9, 10] by X-ray absorption near edge spectroscopy (XANES) and time-resolved optical spectroscopy. They detected local deformations of ligands and the excitation of various vibron modes at the transition of the Fe2+ ion from a low-spin (LS) to high-spin (HS) state. Iron oxides with the Fe3+ and Fe2+ ions with the HS ground state, where the spin crossover to the LS state occurs at high pressures, constitute another important class of compounds with spin crossover [13].
In this work, we consider the ultrafast quantum relaxation dynamics of the photoexcited state with the spin different from the spin of the ground state (which can be called the dynamic spin crossover) in magnetically ordered materials with allowance for the spin– orbit coupling between the HS and LS states and the electron–vibration interaction beyond the adiabatic approximation. A feature of magnetically ordered systems is the interatomic exchange interaction, which, together wi
Data Loading...
