Electron Spin Polarization in Resonant Interband Tunneling Devices

We study spin-dependent interband resonant tunneling in double-barrier InAs/AlSb/ GaMnSb heterostructures. We demonstrate that these structures can be used as spin filters utilizing spin-selective tunneling of electrons through the light-hole resonant channel. High densities of the spin polarized electrons injected into bulk InAs make spin resonant tunneling devices a viable alternative for injecting spins into a semiconductor. Another striking feature of the proposed devices is the possibility of inducing additional resonant channels corresponding to the heavy holes. This can be implemented by saturating the in-plane magnetization in the quantum well.Comment: 11 pages, 4 eps figure

PRESSURE DEPENDENCE OF IMPURITY INDUCED RAMAN SCATTERING SPECTRA I N ZnS CRYSTALS

Raman scattering from zinc sulphide crystals containing a transition metal substitutional impurity (Mn and Co) is reported at different pressures up to 40 kbar. Numerical calculations of these impurity induced Raman intensities are also made on the basis of Green's function theory. It is shown that the features observed in the Raman spectra of the above crystals may be interpreted as a series of resonant modes due to the weakening of the impurity-sulfur bonds by about 20 %

Impurity-induced phonon disordering in Cd1-xZnxTe ternary alloys

10.1103/PhysRevB.48.17064Physical Review B482317064-1707

Balancing vectors in any norm

In the vector balancing problem, we are given symmetric convex bodies C and K in ℝn, and our goal is to determine the minimum number β ≥ 0, known as the vector balancing constant from C to K, such that for any sequence of vectors in C there always exists a signed combination of them lying inside βK. Many fundamental results in discrepancy theory, such as the Beck-Fiala theorem (Discrete Appl. Math '81), Spencer's "six standard deviations suffice" theorem (Trans. Amer. Math. Soc '85) and Banaszczyk's vector balancing theorem (Random Structures & Algorithms '98) correspond to bounds on vector balancing constants. The above theorems have inspired much research in recent years within theoretical computer science. In this work, we show that all vector balancing constants admit "good" approximate characterizations, with approximation factors depending only polylogarithmically on the dimension n. First, we show that a volumetric lower bound due to Banaszczyk is tight within a O(log n) factor. Our proof is algorithmic, and we show that Rothvoss's (FOCS '14) partial coloring algorithm can be analyzed to obtain these guarantees. Second, we present a novel convex program which encodes the "best possible way" to apply Banaszczyk's vector balancing theorem for bounding vector balancing constants from above, and show that it is tight within an O(log2.5 n) factor. This also directly yields a corresponding polynomial time approximation algorithm both for vector balancing constants, and for the hereditary discrepancy of any sequence of vectors with respect to an arbitrary norm