Seminars Archive

Ultrafast Dynamics of Charge- and Spin-Stripes in La_1.75Sr_0.25NiO₄

Abstract
Ultrafast techniques provide the important ability to transiently excite correlated systems into non-thermal phases, and the ensuing relaxation dynamics can provide the ability to distinguish otherwise entangled degrees-of-freedom in the time domain. In this seminar I will report on the first ultrafast mid-infrared spectroscopy and time-resolved x-ray diffraction study of a charge and spin-ordered nickelate. The combination of the two techniques shines light on the complex dynamics of this correlated material, revealing a non-thermal response to optical excitation. While X-ray diffraction provides information on the dynamics of long-range ordering of both charge- and spin-stripes, ultrafast optical spectroscopy allows disentangling short-range charge correlations to the lattice degree-of-freedom by measuring the fast recovery (about 600 fs) of the correlation pseudogap. This result allows estimation of the electron-phonon coupling constant and comparison to polaronic models of charge localization in nickelates.