scholarly journals Optically induced transient enhancement of a structural order parameter

2019 ◽  
Vol 205 ◽  
pp. 07001
Author(s):  
M. Porer ◽  
M. Fechner ◽  
E. M. Bothschafter ◽  
L. Rettig ◽  
A. Narayan ◽  
...  
Keyword(s):  
Order Parameter ◽  
Soft Mode ◽  
X Rays ◽  
Rapid Decay ◽  
Structural Order ◽  
Distorted Phase ◽  
Optically Induced

We photoexcite SrTiO3 and EuTiO3 in their purely soft-mode-driven structurally distorted phase and trace the structural order parameter via ultra-short x-rays. We observe a rapid decay for SrTiO3 and an intriguing transient enhancement for EuTiO3.

scholarly journals Manifestation of magnetoelastic interactions in Raman spectra of HoxNd1−xFe3(BO3)4 crystals

2018 ◽  
Vol 08 (02) ◽  
pp. 1850011 ◽  
Author(s):  
A. S. Krylov ◽  
S. N. Sofronova ◽  
I. A. Gudim ◽  
S. N. Krylova ◽  
Rajesh Kumar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectra ◽  
Structural Phase Transition ◽  
Solid Solutions ◽  
Order Parameter ◽  
Soft Mode ◽  
Magnetic Phase ◽  
Structural Phase ◽  
Exchange Interactions ◽  
Magnetoelastic Interaction

Raman spectra of Ho[Formula: see text]NdxFe(BO3)4 ([Formula: see text], 0.75, 0.5, 0.25) have been studied in temperature range 10–400[Formula: see text]K. Two compositions ([Formula: see text], [Formula: see text]) demonstrate structural phase transition with soft mode restoration. The addition of Nd atoms increases interatomic spacing and decreases the temperature of structural phase transition. The solid solutions ([Formula: see text], 0.5, 0.25) demonstrate the emergence of the peaks corresponding to magnetoelastic interaction below Néel temperature. The order parameter of the magnetic phase transition has been determined. The equal concentrations of holmium and neodymium atoms prevent magnon soft modes condensation caused by exchange interactions in Fe–O–Fe chains are observed. Calculations confirm the data obtained in the experiment.

Calculation of the Raman Linewidths of Lattice Modes Close to the α-β Transition in Quartz

2012 ◽  
Vol 31 (6) ◽  
pp. 741-747 ◽  
Author(s):  
Mustafa Cem Lider ◽  
Hamit Yurtseven
Keyword(s):  
Experimental Data ◽  
Critical Exponent ◽  
Power Law ◽  
Order Parameter ◽  
Quartz Crystal ◽  
Soft Mode ◽  
Energy Fluctuation ◽  
Mode Behavior ◽  
Lattice Mode ◽  
Lattice Modes

AbstractThe Raman frequencies of the lattice modes (147 cm−1 and 207 cm−1) are analyzed for the α-β transition in quartz according to a power-law formula with the critical exponent by using the experimental data. The temperature dependence of the Raman frequency is associated with the order parameter (polarization P) for this transition in the quartz crystal.The damping constant of the lattice modes studied here is calculated using the Raman frequencies at various temperatures for the α-β transition in quartz (Tc = 846 K) using the soft mode – hard mode and the energy fluctuation models. Our calculations for the damping constant (bandwidths) give an evidence that the lattice mode of the 147 cm−1 exhibits a soft mode behavior for the α-β transition in quartz.

Effect of dislocations on the structural order parameter in a crystal upon torsional strain

2017 ◽  
Vol 59 (11) ◽  
pp. 2290-2295 ◽  
Author(s):  
Yu. D. Zavorotnev ◽  
A. Yu. Zakharov ◽  
L. S. Metlov
Keyword(s):  
Order Parameter ◽  
Torsional Strain ◽  
Structural Order

Désordre linéaire dans les cristaux (cas du silicium, du quartz, et des pérovskites ferroélectriques)

1970 ◽  
Vol 26 (2) ◽  
pp. 244-254 ◽  
Author(s):  
R. Comès ◽  
M. Lambert ◽  
A. Guinier
Keyword(s):  
Inelastic Scattering ◽  
Radiation Damage ◽  
Elastic Properties ◽  
Diffuse Scattering ◽  
Major Part ◽  
Alternative Explanation ◽  
Soft Mode ◽  
X Rays ◽  
Neutron Inelastic Scattering ◽  
Thermal Vibrations

Many crystals produce a diffuse scattering of X-rays which is localized in a series of relplanes. It is shown that the corresponding linear disorder in the crystal may have various origins. In silicon, the scattering is due to thermal vibrations and is well explained by the elastic properties of the crystal. In neutron irradiated quartz the radiation damage is responsible for the major part of the scattering. The case of BaTiO3 and KNbO3 is discussed in detail. A linear disorder is proposed which accounts better for the different distributions of the scattering in the 4 allotropic phases than the alternative explanation of the soft mode. In spite of some neutron inelastic scattering results it is not yet possible to distinguish between static and dynamic disorder.

scholarly journals Autonomously revealing hidden local structures in supercooled liquids

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Emanuele Boattini ◽  
Susana Marín-Aguilar ◽  
Saheli Mitra ◽  
Giuseppe Foffi ◽  
Frank Smallenburg ◽  
...  
Keyword(s):  
Machine Learning ◽  
Disordered Systems ◽  
Order Parameter ◽  
Learning Algorithm ◽  
Structural Characteristics ◽  
Supercooled Liquids ◽  
Machine Learning Techniques ◽  
Unsupervised Machine Learning ◽  
Local Structures ◽  
Structural Order

Abstract Few questions in condensed matter science have proven as difficult to unravel as the interplay between structure and dynamics in supercooled liquids. To explore this link, much research has been devoted to pinpointing local structures and order parameters that correlate strongly with dynamics. Here we use an unsupervised machine learning algorithm to identify structural heterogeneities in three archetypical glass formers—without using any dynamical information. In each system, the unsupervised machine learning approach autonomously designs a purely structural order parameter within a single snapshot. Comparing the structural order parameter with the dynamics, we find strong correlations with the dynamical heterogeneities. Moreover, the structural characteristics linked to slow particles disappear further away from the glass transition. Our results demonstrate the power of machine learning techniques to detect structural patterns even in disordered systems, and provide a new way forward for unraveling the structural origins of the slow dynamics of glassy materials.

scholarly journals Structural order as a genuine control parameter of dynamics in simple glass formers

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Hua Tong ◽  
Hajime Tanaka
Keyword(s):  
Glass Transition ◽  
Order Parameter ◽  
Liquid Structure ◽  
Coarse Grained ◽  
Glassy Dynamics ◽  
Slowing Down ◽  
Structural Order ◽  
Particle Level ◽  
Complex Structural ◽  
Unified Description

AbstractGlass transition is characterised by drastic dynamical slowing down upon cooling, accompanied by growing spatial heterogeneity. Its rationalisation by subtle changes in the liquid structure has been long debated but remains elusive, due to intrinsic difficulty in detecting the underlying complex structural ordering. Here we report that structural order parameter characterising local packing capability can well describe the glassy dynamics not only macroscopically but also microscopically, no matter whether it is driven by temperature or density. A Vogel-Fulcher-Tammann (VFT)-like relation is universally identified between the structural relaxation time and the order parameter for supercooled liquids with isotropic interactions. More importantly, we find such an intriguing VFT-like relation to be statistically valid even at a particle level, between spatially coarse-grained structural order and microscopic particle-level dynamics. Such a unified description of glassy dynamics based solely on structural order is expected to contribute to the ultimate understanding of the long-standing glass-transition problem.

TEMPERATURE DEPENDENCE OF THE DAMPING CONSTANT CLOSE TO THE I–II PHASE TRANSITION IN s-TRIAZINE

2010 ◽  
Vol 24 (03) ◽  
pp. 369-380 ◽  
Author(s):  
D. KAVRUK ◽  
H. YURTSEVEN
Keyword(s):  
Phase Transition ◽  
Temperature Dependence ◽  
Mode Coupling ◽  
Order Parameter ◽  
Input Data ◽  
Soft Mode ◽  
Coupling Model ◽  
Acoustic Mode ◽  
Raman Mode ◽  
Mode Ii

The damping constant is calculated here at various temperatures for the Raman mode II in s-triazine using the soft mode–hard mode coupling model. The temperature dependence of the order parameter is used as the input data to calculate the damping constant of the Raman mode studied in this coupling model for s-triazine close to the I–II transition (Tc = 198 K ). The soft mode–hard mode coupling model which considers the coupling of the soft acoustic mode with the optic modes in s-triazine, is fitted to the observed halfwidths of the Raman mode II close to the I–II phase transition in this crystal.

scholarly journals Microscopic order parameter of two nematogenic compounds using X-rays

1999 ◽  
Vol 22 (2) ◽  
pp. 129-132 ◽  
Author(s):  
A P Divya ◽  
D Revannasiddaiah ◽  
R Somashekar ◽  
M S Madhava
Keyword(s):  
Order Parameter ◽  
X Rays
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