990 research outputs found
Low-Frequency Raman Modes and Electronic Excitations In Atomically Thin MoS2 Crystals
Atomically thin MoS crystals have been recognized as a quasi-2D
semiconductor with remarkable physics properties. This letter reports our Raman
scattering measurements on multilayer and monolayer MoS, especially in
the low-frequency range (50 cm). We find two low-frequency Raman
modes with contrasting thickness dependence. With increasing the number of
MoS layers, one shows a significant increase in frequency while the other
decreases following a 1/N (N denotes layer-number) trend. With the aid of
first-principle calculations we assign the former as the shear mode
and the latter as the compression vibrational mode. The opposite
evolution of the two modes with thickness demonstrates novel vibrational modes
in atomically thin crystal as well as a new and more precise way to
characterize thickness of atomically thin MoS films. In addition, we
observe a broad feature around 38 cm (~5 meV) which is visible only
under near-resonance excitation and pinned at the fixed energy independent of
thickness. We interpret the feature as an electronic Raman scattering
associated with the spin-orbit coupling induced splitting in conduction band at
K points in their Brillouin zone.Comment: 5 pages, 4 figure
Improving Cell Surface Functional Expression of Delta F508 CFTR: A Quest for Therapeutic Targets
Model reduction of synchronized homogeneous Lur'e networks with incrementally sector-bounded nonlinearities
This paper proposes a model order reduction scheme that reduces the complexity of diffusively coupled homogeneous Lur'e systems. We aim to reduce the dimension of each subsystem and meanwhile preserve the synchronization property of the overall network. Using the Laplacian spectral radius, we characterize the robust synchronization of the Lur'e network by a linear matrix inequality (LMI), whose solutions then are treated as generalized Gramians for the balanced truncation of the linear component of each Lur'e subsystem. It is verified that, with the same communication topology, the resulting reduced-order network system is still robustly synchronized, and an a priori bound on the approximation error is guaranteed to compare the behaviors of the full-order and reduced-order Lur'e subsystems
- β¦