Spin-dependent THz oscillator based on hybrid graphene superlattices

We theoretically study the occurrence of Bloch oscillations in biased hybrid graphene systems with spin-dependent superlattices. The spin-dependent potential is realized by a set of ferromagnetic insulator strips deposited on top of a gapped graphene nanoribbon, which induce a proximity exchange splitting of the electronic states in the graphene monolayer. We numerically solve the Dirac equation and study Bloch oscillations in the lowest conduction band of the spin-dependent superlattice. While the Bloch frequency is the same for both spins, we find the Bloch amplitude to be spin dependent. This difference results in a spin-polarized ac electric current in the THz range.Comment: 4 pages, 6 figure

Speed of sound in disordered Bose-Einstein condensates

Disorder modifies the sound-wave excitation spectrum of Bose-Einstein condensates. We consider the classical hydrodynamic limit, where the disorder correlation length is much longer than the condensate healing length. By perturbation theory, we compute the phonon lifetime and correction to the speed of sound. This correction is found to be negative in all dimensions, with universal asymptotics for smooth correlations. Considering in detail optical speckle potentials, we find a quite rich intermediate structure. This has consequences for the average density of states, particularly in one dimension, where we find a "boson dip" next to a sharp "boson peak" as function of frequency. In one dimension, our prediction is verified in detail by a numerical integration of the Gross-Pitaevskii equation.Comment: final, extended version with 2 new figure

Femtosecond Pump-Probe Diagnostics Of Preformed Plasma Channels

We report on recent ultrafast pump-probe experiments 28 in He plasma waveguides using 800 nm, 80 fs pump pulses of 0.2 x 1018 W/cm2 peak guided intensity, and single orthogonally-polarized 800 nm probe pulses with similar to0.1% of pump intensity. The main results are: (1) We observe frequency-domain interference between the probe and a weak, depolarized component of the pump that differs substantially in mode shape from the injected pump pulse; (2) we observe spectral blue-shifts in the transmitted probe that are not evident in the transmitted pump. The evidence indicates that pump depolarization and probe blue-shifts both originate near the channel entrance.Physic

Summary Report Of Working Group 8: Laser Technology For Laser-Plasma Accelerators

Laser Technology has long been the limiting and the enabling step for laser plasma accelerators. The work presented here addressed the current and near future laser technology relevant to particle acceleration as well as laser technology challenges for future accelerator facilities. Many laser facilities are operating or will be operating shortly at high intensity, high peak power, and with good beam parameters.Physic

CIRCUITS BASED ON MAGNETOELECTRIC TRANSISTOR DEVICES

Logic circuits constructed with magnetoelectric (ME) transistors are described herein. A ME logic gate device can include at least one conducting device, for example, at least one MOS transistor; and at least one ME transistor coupled to the at least one conducting device. The ME transistor can be a ME field effect transistor (ME-FET), which can be can be an anti-ferromagnetic spin-orbit read (AFSOR) device or a non - AFSOR device. The gates and logic circuits described herein can be included as standard cells in a design library. Cells of the cell library can include standard cells for a ME verter device, a ME minority gate device, a ME majority gate device, a ME full adder, a ME XNOR device, a ME XOR device, or a combination thereof