Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAn Inelastic X-Ray investigation of the Ferroelectric Transition in SnTe
102
0
0.0
(
0
)
Added by
Christopher O'Neill
Publication date
2017
fields
Physics
and research's language is
English
Authors
Christopher D. ONeill
Ask ChatGPT about the research
No Arabic abstract
We report that the lowest energy transverse-optic phonon in metallic SnTe softens to near zero energy at the structural transition at $T_C=75 text{~K}$ and importantly show that the energy of this mode below $T_C$ increases as the temperature decreases. Since the mode is a polar displacement this proves unambiguously that SnTe undergoes a ferroelectric displacement below $T_C$. Concentration gradients and imperfect stoichiometry in large crystals may explain why this was not seen in previous inelastic neutron scattering studies. Despite SnTe being metallic we find that the ferroelectric transition is similar to that in ferroelectric insulators, unmodified by the presence of conduction electrons: we find that (i) the damping of the polar mode is dominated by coupling to acoustic phonons rather than electron-phonon coupling (ii) the transition is almost an ideal continuous transition (iii) comparison with density functional calculations identifies the importance of dipolar-dipolar screening for understanding this behaviour.
rate research
Read More
We present the full in-plane phonon dispersion of graphite obtained from inelastic x-ray scattering, including the optical and acoustic branches, as well as the mid-frequency range between the $K$ and $M$ points in the Brillouin zone, where experimental data have been unavailable so far. The existence of a Kohn anomaly at the $K$ point is further supported. We fit a fifth-nearest neighbour force-constants model to the experimental data, making improved force-constants calculations of the phonon dispersion in both graphite and carbon nanotubes available.
Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest. Here we show that the nonlinear interactions between two optical phonons in SnTe, a two-dimensional in-plane ferroelectric material, enables a dynamical amplification of the electric polarization within subpicoseconds time domain. Our first principles time dependent simulations show that the infrared-active out-of-plane phonon mode, pumped to nonlinear regimes, spontaneously generates in-plane motions, leading to rectified oscillations in the in-plane electric polarization. We suggest that this dynamical control of ferroelectric material, by nonlinear phonon excitation, can be utilized to achieve ultrafast control of the photovoltaic or other non-linear optical responses.
The structural investigations of nanomaterials motivated by their large variety and diverse set of applications have attracted considerable attention. In particular, the ever-improving machinery, both in laboratory and at large scale facilities, together with the methodical improvements available for studying nanostructures ranging from epitaxial nanomaterials, nanocrystalline thin films and coatings, to nanoparticles and colloidal nanocrystals allows us to gain a more detailed understanding of their structural properties. As the structure essentially determines the physical properties of the materials, this advances the possibilities of structural studies and also enables a deeper understanding of the structure to property relationships. In this special issue entitled Investigation of Nanostructures with X-ray Scattering Techniques five contributions show the recent progress in various research fields. Contributions cover topics as diverse as neutron scattering on magnetic multilayer films, epitaxial orientation of organic thin films, nanoparticle ordering and chemical composition analysis, and the combination of nanofocused X-ray beams with electrical measurements.
The realization of multiferroicity in 2D nanomaterials is crucially important for designing advanced nanoelectronic devices such as non-volatile multistate data storage. In this work, the coexistence of ferromagnetism and ferroelectricity is reported in monolayer SnTe system by transition metal (TM) doping. Based on first-principles calculations, the spontaneous spin polarization could be realized by TM doping in ferroelectric SnTe monolayer. In addition to in-plane ferroelectric polarization, the out-of-plane ferroelectric polarization emerges in Mn (Fe)-doped SnTe monolayer due to the internal displacement of TM from the surface. Interestingly, the crystalline field centered on TM and interaction between the dopant and Te gradually enhanced with the increment of atomic number of doping elements, which explains why the formation energy decreases. The realization of multiferroics in SnTe monolayer could provide theoretical guidance for experimental preparation of low-dimensional multiferroic materials.
Epitaxial BiFeO3/SrRuO3 superlattices have been grown by pulsed laser deposition on a (001) oriented LaAlO3 substrate and probed by X-ray diffraction and Raman spectroscopy. To investigate the structural competition between rhombohedral BiFeO3 and orthorhombic SrRuO3 the total thickness of all SLs was kept constant and the bilayer thickness (period) {Lambda} was varied. The interlayer strain effects are therefore tuned from large strain effects (short {Lambda} period) to quasi-relaxed structure (large {Lambda}). A complementary investigation using X-ray diffraction and phonon dynamics hints to change from a rhombohedral to a tetragonal structure in the superlattices with the increase of the interlayer strain effect.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
