Seminars Archive

Femtosecond Stimulated Raman Scattering

Abstract
Manipulating the macroscopic phases of solids via optical stimuli is a fascinating perspective. Indeed, the optical control of fundamental interactions has aroused growing interest in condensed matter physics, such as metal-insulator transitions and superconductivity [1]. Femtosecond Stimulated Raman Scattering (FSRS) is a vibrational sensitive experimental technique with unrestricted time precision and energy resolution; it allows detecting optically-driven dynamics of solid phase in the sub-picosecond timescale. I will briefly introduce the FSRS experimental setup developed at the Femtoscopy labs in Rome, and then focus on a time resolved study of the exchange energy (Eex) photo-induced dynamics in a prototype Heisenberg antiferromagnet, namely the cubic perovskite KNiF₃. Tracking the temporal evolution of the two-magnon line (2ML) in the blue and red side of the Raman excitation, we unveil a sub-100 fs photo-induced dynamics of the 2ML [2]. Such result provides an estimate of the 2ML dissipative dynamics, setting an experimental benchmark for theoretical descriptions of ultrafast laser-induced magnetic dynamics beyond the Heisenberg model. Moreover, we establish a protocol to obtain the correct dynamics of a Raman mode from FSRS measurements, when timescales are as short as the duration of the pump and probe pulses. We anticipate that an investigation of the 2ML dynamics, triggered by resonant excitation of the charge-transfer transition would reveal different pathways for optical control of the exchange energy.

References:
[1] A. Kirilyuk, A. V. Kimel, T. Rasing, Rev. Mod. Phys. 82, 2731–2784 (2010).
[2] G. Batignani, D. Bossini, N. Di Palo, C. Ferrante, E. Pontecorvo, G. Cerullo, A. Kimel, T. Scopigno, Nature Photonics, 9, 506-510 (2015)