Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNanoscale Bandgap Tuning across an Inhomogeneous Ferroelectric Interface
182
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report nanoscale bandgap engineering via a local strain across the inhomogeneous ferroelectric interface, which is controlled by the visible-light-excited probe voltage. Switchable photovolatic effects and the spectral response of the photocurrent were explore to illustrate the reversible bandgap variation (~0.3eV). This local-strain-engineered bandgap has been further revealed by in situ probe-voltage-assisted valence electron energy-loss spectroscopy (EELS). Phase-field simulations and first-principle calculations were also employed for illustration of the large local strain and the bandgap variation in ferroelectric perovskite oxides. This reversible bandgap tuning in complex oxides demonstrates a framework for the understanding of the opticallyrelated behaviors (photovoltaic, photoemission, and photocatalyst effects) affected by order parameters such as charge, orbital, and lattice parameters.
rate research
Read More
Despite the ubiquity of applications of heat transport across nanoscale interfaces, including integrated circuits, thermoelectrics, and nanotheranostics, an accurate description of phonon transport in these systems remains elusive. Here we present a theoretical and computational framework to describe phonon transport with position, momentum and scattering event resolution. We apply this framework to a single material spherical nanoparticle for which the multidimensional resolution offers insight into the physical origin of phonon thermalization, and length-scale dependent anisotropy of steady-state phonon distributions. We extend the formalism to handle interfaces explicitly and investigate the specific case of semi-coherent materials interfaces by computing the coupling between phonons and interfacial strain resulting from aperiodic array of misfit dislocations. Our framework quantitatively describes the thermal interface resistance within the technologically relevant Si-Ge heterostructures. In future, this formalism could provide new insight into coherent and driven phonon effects in nanoscale materials increasingly accessible via ultrafast, THz and near-field spectroscopies.
Nanoplasmonic systems combined with optically-active two-dimensional materials provide intriguing opportunities to explore and control light-matter interactions at extreme sub-wavelength lengthscales approaching the exciton Bohr radius. Here, we present room- and cryogenic-temperature investigations of light-matter interactions between an MoSe$_2$ monolayer and individual lithographically defined gold dipole nanoantennas having sub-10 nm feed gaps. By progressively tuning the nanoantenna size, their dipolar resonance is tuned relative to the A-exciton transition in a proximal MoSe$_2$ monolayer achieving a total tuning of $sim 130;mathrm{meV}$. Differential reflectance measurements performed on $> 100$ structures reveal an apparent avoided crossing between exciton and dipolar mode and an exciton-plasmon coupling constant of $g= 55;mathrm{meV}$, representing $g/(hbaromega_X)geq3%$ of the transition energy. This places our hybrid system in the intermediate-coupling regime where spectra exhibit a characteristic Fano-like shape, indicative of the interplay between pronounced light-matter coupling and significant damping. We also demonstrate active control of the optical response by varying the polarization of the excitation light to programmably suppress coupling to the dipole mode. We further study the emerging optical signatures of the monolayer localized at dipole nanoantennas at $10;mathrm{K}$. Our findings represent a key step towards realizing non-linear photonic devices based on 2D materials with potential for low-energy and ultrafast performance.
Topological spin textures can serve as non-volatile information carriers. Here we study the current-induced dynamics of magnetic skyrmions on a nanoscale square grid formed by orthogonal defect lines with reduced magnetic anisotropy. A skyrmion on the square grid is pixelated with a quantized size of the grid. We demonstrate that the position, size, and shape of skyrmions on the square grid are electrically configurable, which can be used to store digital information. The skyrmion center is quantized to be on the grid and the skyrmion shows a hopping motion instead of a continuous motion. We find that the skyrmion Hall effect can be perfectly prohibited due to the pinning effect of the grid. The pixelated skyrmions can be harnessed to build the programmable racetrack memory, multistate memory, and logic computing device. Our results will be a basis for future digital computation based on pixelated topological spin textures.
The interface between graphene and the ferroelectric superlattice $mathrm{PbTiO_3/SrTiO_3}$ (PTO/STO) is studied. Tuning the transition temperature through the PTO/STO volume fraction minimizes the adsorbates at the graphene-ferroelectric interface, allowing robust ferroelectric hysteresis to be demonstrated. Intrinsic charge traps from the ferroelectric surface defects can adversely affect the graphene channel hysteresis, and can be controlled by careful sample processing, enabling systematic study of the charge trapping mechanism.
Phonon transmission across an interface between dissimilar crystalline solids is calculated using molecular dynamics simulations with interatomic force constants obtained from first principles. The results reveal that although inelastic phonon-transmission right at the geometrical interface can become far greater than the elastic one, its contribution to thermal boundary conductance (TBC) is severely limited by the transition regions, where local phonon states at the interface recover the bulk state over a finite thickness. This suggests TBC can be increased by enhancing phonon equilibration in the transition region for instance by phonon scattering, which is demonstrated by increasing the lattice anharmonicity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
