磁性纳米粒子超快动力学的局域控制

Quantitative nanoparticle structures from ultrafast electron crystallography data

We describe the quantitative refinement of nanoparticle structures from gold nanoparticles probed by ultrafast electron crystallography (UEC). We establish the equivalence between the modified radial distribution function employed in UEC and the atomic pair distribution function (PDF) used in x-ray and neutron powder diffraction analysis. By leveraging PDF refinement techniques, we demonstrate that UEC data are of sufficient quality to differentiate between cuboctahedral, decahedral and icosahedral nanoparticle models. Furthermore, we identify the signatures of systematic errors that may occur…

Spontaneous Emission and Ultrafast Carrier Relaxation in InGaN Quantum Well with Metal Nanoparticles

Subpicosecond wavelength non-degenerate differential transmission (DT) was used to observe the carrier relaxation mechanism in GaN based quantum well (QW) with and without metal nanoparticles (MNPs) in it. The spontaneous emission dominates the stimulated emission for above the GaN band edge excitation energy. We observed long decay times for Au-embedded sample and short decay times for Ag-embedded sample with respect to reference sample.

双磁隧道结的超快无惯性切换

Ultrafast inertia-free switching of double magnetic tunnel junctions

本文研究双磁隧道结存储单元中磁性纳米粒子在自旋极化电流和弱磁场下的超快无惯性切换，确定了100皮秒范围内最小功耗的脉冲参数，为高性能非易失性存储器提供新方案。

All-Optical Ultrafast Control and Read-Out of a Single Negatively Charged Self-Assembled InAs Quantum Dot

We demonstrate the all-optical ultrafast manipulation and read-out of optical transitions in a single negatively charged self-assembled InAs quantum dot, an important step towards ultrafast control of the resident spin. Experiments performed at zero magnetic field show the excitation and decay of the trion (negatively charged exciton) as well as Rabi oscillations between the electron and trion states. Application of a DC magnetic field perpendicular to the growth axis of the dot enables observation of a complex quantum beat structure produced by independent precession of the ground state elect…

Controlling ultrafast currents by the non-linear photogalvanic effect

We theoretically investigate the effect of broken inversion symmetry on the generation and control of ultrafast currents in a transparent dielectric (SiO2) by strong femto-second optical laser pulses. Ab-initio simulations based on time-dependent density functional theory predict ultrafast DC currents that can be viewed as a non-linear photogalvanic effect. Most surprisingly, the direction of the current undergoes a sudden reversal above a critical threshold value of laser intensity I_c ~ 3.8*10^13 W/cm2. We trace this switching to the transition from non-linear polarization currents to the tu…