Fascinating optical properties governed by extremely confined excitons have been so far observed in 2D crystals like monolayers of transition metal dichalcogenides. These materials, however, are ...limited for production by epitaxial methods. Besides, they are not suitable for the development of optoelectronics for the challenging deep-ultraviolet spectral range. Here, we present a single monolayer of GaN in AlN as a heterostructure fabricated by molecular beam epitaxy, which provides extreme 2D confinement of excitons, being ideally suited for light generation in the deep-ultraviolet. Optical studies in the samples, supplemented by a group-theory analysis and first-principle calculations, make evident a giant enhancement of the splitting between the dark and bright excitons due to short-range electron–hole exchange interaction that is a fingerprint of the strongly confined excitons. The practical significance of our results is in the observation of the internal quantum yield of the room-temperature excitonic emission as high as ∼75% at 235 nm.
It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley ...relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 10(6) m s(-1) remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe.
Logistic sigmoids due to their flexibility seem to be natural candidates for modelling macrofinancial leverage behavior. The sigmoidal leverage transition towards its stationary value, which was ...driven by the yield spreads, could have replicated the dynamics of macrofinancial assets, debt and capital. The leverage transition, in its turn, has been a major factor in better balancing macrofinancial liabilities and assets. The sigmoidal leverage trajectories including their inflections and different phases were identified by a nonlinear transition function providing information necessary for steering the process towards its stable state. Solving the stationary Kolmogorov-Fokker-Plank logistic equation revealed that random leverage realizations might follow the gamma distribution. Parameters of its stationary probability density function, as well as the expected and the modal leverage, were dependent on the process variance and the yield spreads. Thus, the stochastic leverage behaviour reproduced a sequence of stylized phases similar to the observed in the US Treasuries market meltdown in 2020. In particular, larger yield spreads and smaller modal leverage signalled a "defensive" market response to sudden volatility increases. In addition, it was shown that the logistic leverage modelling could be helpful in the analysis of debt and money dynamics including some consequences of "minting a one trillion dollars coin".
The electronic properties of graphene depends on how many layers are involved. Monolayer graphene is a zero-gapped semi-metal. Bilayer graphene is a small-gapped semiconductor. Magnetotransport ...measurements indicate trilayer graphene can be both, depending on its stacking.
Much of computer‐generated animation is created by manipulating meshes with rigs. While this approach works well for animating articulated objects like animals, it has limited flexibility for ...animating less structured free‐form objects. We introduce Wassersplines, a novel trajectory inference method for animating unstructured densities based on recent advances in continuous normalizing flows and optimal transport. The key idea is to train a neurally‐parameterized velocity field that represents the motion between keyframes. Trajectories are then computed by advecting keyframes through the velocity field. We solve an additional Wasserstein barycenter interpolation problem to guarantee strict adherence to keyframes. Our tool can stylize trajectories through a variety of PDE‐based regularizers to create different visual effects. We demonstrate our tool on various keyframe interpolation problems to produce temporally‐coherent animations without meshing or rigging.
Spin Noise in Birefringent Media Kozlov, V. O.; Kuznetsov, N. S.; Smirnov, D. S. ...
Physical review letters,
08/2022, Letnik:
129, Številka:
7
Journal Article
Here, we present a temperature (T) dependent comparison between field-effect and Hall mobilities in field-effect transistors based on few-layered WSe2 exfoliated onto SiO2. Without dielectric ...engineering and beyond a T-dependent threshold gate-voltage, we observe maximum hole mobilities approaching 350 cm(2)/Vs at T = 300 K. The hole Hall mobility reaches a maximum value of 650 cm(2)/Vs as T is lowered below ~150 K, indicating that insofar WSe2-based field-effect transistors (FETs) display the largest Hall mobilities among the transition metal dichalcogenides. The gate capacitance, as extracted from the Hall-effect, reveals the presence of spurious charges in the channel, while the two-terminal sheet resistivity displays two-dimensional variable-range hopping behavior, indicating carrier localization induced by disorder at the interface between WSe2 and SiO2. We argue that improvements in the fabrication protocols as, for example, the use of a substrate free of dangling bonds are likely to produce WSe2-based FETs displaying higher room temperature mobilities, i.e. approaching those of p-doped Si, which would make it a suitable candidate for high performance opto-electronics.
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