Ultrafast and Fast Structural Dynamics
of Photoinduced Transformations in Molecular Materials
Outline 1 – Structural Dynamics and Photo-InducedTransformations in Materials 2 – Tracking the Time Evolution of Molecular Switching in the Solid State 3 – Capturing Precursors of a Photo- Induced Transformation in a Material
Outline 1 – Structural Dynamics and Photo-InducedTransformations in Materials 2 – Tracking the Time Evolution of Molecular Switching in the Solid State 3 – Capturing Precursors of a Photo- Induced Transformation in a Material
Not only to observe matter, on ever smallest scale, but also to direct its functionality at the relevant lenght, time and energy scales
ADVENT OF CONTROL SCIENCE
from BESAC report
Nanometric
Ground State
Transient state
Lattice Relaxation
False Ground State
New Lattice
Structure and
Electronic Order
cooperativity
from K.
Nasu Light pulse may direct the functionality of a material through collective and/or cooperative photoinduced phenomena. Due to interactions between photo-excited constituents, positive feedback can trigger the non-equilibrium transformation of the material towards another macroscopic state of different electronic and/or structural order.
« More is Different » (P. Anderson) response
Cooperativity Nonlinearity
Coherence Far away from Equilibrium
time
perturbation
configuration
system
feedback
Multiscale dynamical processes
In a given time scale, typical for the dynamics of certain degrees of freedom (for instance atomic motions), some other degrees of freedom are faster and acts by their quantum or statistical average, while other ones are slower and then frozen. This leads to decoupling effects and steps in the physical picture of the transformation. Therefore, there is not an unique dynamical description valid at every time scales (not an unique equation to describethe time evolution, not an unique potential energy landscape).
Shock wave Srain propagation
Electronic motion
1 s
10-3 s
10-6 s
10-15 s
days
Atomic motion Optical phonon
Different time-scales
10-9 s
10-12 s
10-15 s
Laser pump and X-ray probe
Watching how material
transforms
from K. Nelson Science (1999)
from 100 ps
to 100 fs
New avenue in structural dynamics
Bragg peaks : long range order position : lattice shape : size and shape of blocks intensity : average cell structure
Diffuse scattering : short range order position : local periodic fluctuation shape : spatial extend of correlation intensity : fluctuation amplitude
The instantaneous density of a given cell may again be decom- posed between an average over all cells in the crystal and its deviation ρn(r,t) = ρcell(r,t) + ∆ρn(r,t) scattering = Bragg + diffuse
Density and scattering
Outline 1 – Structural Dynamics and Photo-InducedTransformations in Materials 2 – Tracking the Time Evolution of Molecular Switching in the Solid State 3 – Capturing Precursors of a Photo- Induced Transformation in a Material
Spin transition
Spin crossover crystals are the proto-type of molecular bistabilityin the solid state. Molecules can cooperatively switch between two states, here from LS to HS under various external sollici-tations, at thermal equilibrium and out of equilibrium (for instance light irrradia-tion). In general, the phase transition are isostructural, i.e. without change of symmetry - no symmetry breaking. The situation is similar to the gas-liquid phase transition.
• C
P
T
LS HS
Structural dynamics of molecular switching in a Fe (III) compound
weakly cooperative
cf. Poster P2 M. L. Boillot et al.
Ultra-fast molecular relaxation
similar to molecules in solution
Watching swithching dynamics
3 main steps :
i) sub-ps molecular switching ii) unit cell volume expansion
on 10 ns time scale iii) significant thermal effect on µs time scale
Phys. Rev. Letters 103, 028301 (2009) Acta Crys. A 66, 189 (2010)
M. Lorenc et al., PRL 103, 028301 (2009)
1 s
10-3 s
10-6 s
10-9 s
10-12 s
10-15 s
Days
atomic motions optical phonons
acoustic phonons domain wall
motions
Electronic motions
ultra-fast molecular switching (local)
thermalization of lattice at constant volume (isolated)
volume expansion (adiabatic τ ≈ l/vs )
thermal molecular switching and heat diffusion
recovery of thermal equilibrium (τ ≈ C/K)
From the molecular to material scale Consecutive different dynamic processes at different length and time-scales
fs
ps
ns
µs
ms
Non-equilibrium (thermo)dynamics
Q W
H. Cailleau et al., Acta Cryst. A 66, 189 (2010)
<Fhkl(dt)> = XHS(dt) FhklHS(dt)
+ [1-XHS(dt)] FhklLS(dt)
Reorganisation and macroscopic homogeneity
E. Collet et al.,
Chem. Eur. J. 18, 2051 (2012)
X-ray
Light
Molecular switching triggered by volume expansion
M. Lorenc et al., PR B 85, 054302 (2012)
.
10µm / 100nm
Propagating and diffusive phenomena: size and
environment
Monocrystal vs Nanocrystals
MONO NANO .
R.Bertoni et al., Angew. Chem. Int. (2012) and in preparation.
Coherent collective dynamics
Bobsleigh effect
A. Martino, unpublished
Outline 1 – Structural Dynamics and Photo-InducedTransformations in Materials 2 – Tracking the Time Evolution of Molecular Switching in the Solid State 3 – Capturing Precursors of a Photo- Induced Transformation in a Material
from K. Nasu
1D exciton-strings in TTF-CA: detection by diffuse scattering
… A° D° A° (D+ A-) (D+ A-) (D+ A-) D° A° D°...
E. Collet et al, ERL 57(1) 67 (2002) M. Buron et al, PRL 96, 205503 (2006)
Diffuse scattering is very weak
Diffuse Scattering at thermal equilibrium
100 ps experiment at KEK (Japan) The intensity of the diffuse scattering signal increases just after the laser excitation
Time-resolved diffuse scattering
L. Guerin et al. PRL 105, 246101
(2010)
Concluding remarks
Very far to draw a global picture We need : - to extend existing theoretical approaches to new regimes and probably to develop fundamentally new concepts, - to perform challenging experiments using the great potential from advanced probes
IPR Rennes : Roman Bertoni, Hiroshi Watanabe, Ciro D’Amico, Wawrzeniec Kaszub, Andrea Marino,, Marina Servol, Marco Cammarata, Maciej Lorenc, Loic Toupet, Marylise Buron, Eric Collet ICMMO Orsay Marie-Laure Boillot ICMCB Bordeaux Jean-François Létard
ESRF, France Michael Wulff, Laurent Guérin
TITech & KEK Japan Shin-ichi Adachi, Shin-ya Koshihara
Synchrotron Soleil Claire Laulhe, Sylvain Ravy
APS Argonne USA Tim Graber
LCLS Stanford USA Henrik Lemke
Team, Collaborations, Funds
Thank you!