Andrea Cavalleri

Abstract:

Using ultrafast resonant soft x-ray diffraction, we demonstrate photoinduced melting of antiferromagnetic order in the correlated electron insulator NdNiO3. Time-dependent analysis of the resonant diffraction spectra allows us to follow the temporal evolution of the charge imbalance between adjacent Ni sites. A direct correlation between the melting of magnetic order and charge rebalancing is found. Furthermore, we demonstrate that the magnetic ordering on the Ni and Nd sites, which are locked together in equilibrium, become decoupled during this nonthermal process. © 2013 American Physical Society.

Abstract:

Materials with strongly correlated electrons often show rich phase diagramswith dramatic differences in physical properties as doping, applied pressure, or magnetic fields are changed. Even subtle perturbations can cause colossal rearrangements in the electronic spectrum, and irradiation with light can be used to drive spectacular rearrangements in the structural, electronic, and magnetic properties. Here, we discuss the use of THz radiation to selectively excite one single degree of freedom at a time to drive a phase change. This is in contrast to what is done in most studies, which achieve photo-induced phase transitions by non-specific excitation in the visible spectral range. This chapter will combine a summary of developments in instrumentation for strong THz fields with some selected scientific applications of THz control of correlated electron systems. © Springer-Verlag Berlin Heidelberg 2013.