Laser-Induced Ferroelectric Structural Order in an Organic Charge-Transfer Crystal

Abstract

We report the direct observation by x-ray diffraction of a photoinduced paraelectric-to-ferroelectric structural phase transition using monochromatic 100-picosecond synchrotron pulses. It occurs in tetrathiafulvalene-p-chloranil, a charge-transfer molecular material in which electronic and structural changes are strongly coupled. An optical 300-femtosecond laser pulse switches the material from a neutral to an ionic state on a 500-picosecond time scale and, by virtue of intrinsic cooperativity, generates self-organized long-range structural order. The x-ray data indicate a macroscopic ferroelectric reorganization after the laser irradiation. Refinement of the structures before and after laser irradiation indicates structural changes at the molecular level.

Colossal positive and negative thermal expansion and thermosalient effect in a pentamorphic organometallic martensite

“…18). The progression of the habit plane vindicates activation of cooperative processes 23,24 . Taken together with the displacive, diffusionless transition with miniscule rearrangement incurred from the comparative analysis of the molecular packing in a and g, this result strongly supports the view that the TS effect appears in effect of a transition similar to the martensitic transitions in inorganic materials.…”

Picosecond soft x-ray absorption measurement of the photoinduced insulator-to-metal transition inVO2

“…This has been driven in part by developments in tabletop plasma-sources 3,4 , early laser-e-beam interaction schemes 5,6 , fast x-ray detectors 7 and synchrotron instrumentation 8 . Direct detection of photo-excited coherent acoustic 9,10,11 and optical phonons 12 , solid-liquid 13,14,15 and solid-solid 16,17 phase transitions have been recently demonstrated.…”

Aperiodic Spin State Ordering of Bistable Molecules and Its Photoinduced Erasing

“…The control of the functionality of a material requires understanding the complex organization of its atomic or electronic constituents, but also understanding the bi-stable or multi-stable processes addressable by external stimulation, including light for the photo-control 1,2,3,4 . On the one hand, macroscopic ordering is manifested by the appearance of regular patterns, which in some cases never repeat themselves periodically in 3D space but only in a higher dimension space: this so-called aperiodicity 5,6,7 plays a central role in the structure and physical properties of materials as diverse as quasicrystals 8 , charge-density 1 and spin-density waves 9,10 , or new superconductors 11 for instance.…”