Effect of the spin-orbit interaction on the band structure and conductance of quasi-one-dimensional systems

We discuss the effect of the spin-orbit interaction on the band structure, wave functions and low temperature conductance of long quasi-one-dimensional electron systems patterned in two-dimensional electron gases (2DEG). Our model for these systems consists of a linear (Rashba) potential confinement in the direction perpendicular to the 2DEG and a parabolic confinement transverse to the 2DEG. We find that these two terms can significantly affect the band structure introducing a wave vector dependence to subband energies, producing additional subband minima and inducing anticrossings between subbands. We discuss the origin of these effects in the symmetries of the subband wave functions.Comment: 15 pages including 14 figures; RevTeX; to appear in Phys.Rev.B (15 Nov 1999

Dynamical spin-electric coupling in a quantum dot

Due to the spin-orbital coupling in a semiconductor quantum dot, a freely precessing electron spin produces a time-dependent charge density. This creates a sizeable electric field outside the dot, leading to promising applications in spintronics. The spin-electric coupling can be employed for non-invasive single spin detection by electrical methods. We also consider a spin relaxation mechanism due to long-range coupling to electrons in gates and elsewhere in the system, and find a contribution comparable to, and in some cases dominant over previously discussed mechanisms.Comment: 4 pages, 2 figure

Magnetic Resonance of the Intrinsic Defects of the Spin-Peierls Magnet CuGeO3

ESR of the pure monocrystals of CuGeO3 is studied in the frequency range 9-75 GHz and in the temperature interval 1.2-25 K. The splitting of the ESR line into several spectral components is observed below 5 K, in the temperature range where the magnetic susceptibility is suppressed by the spin-Peierls dimerization. The analysis of the magnetic resonance signals allows one to separate the signals of the S=1/2- and S=1 defects of the spin-Peierls phase. The value of g-factor of these signals is close to that of the Cu-ion. The additional line of the magnetic resonance is characterized by an anomalous value of the g-factor and by the threshold-like increase of the microwave susceptibility when the microwave power is increasing. The ESR signals are supposingly attributed to two types of the planar magnetic defects, arising at the boundaries of the domains of the spin-Peierls state with the different values of the phase of the dimerization.Comment: LATEX-text, 12 PS-figures, typos corrected, LATEX-style change

Circularly polarized electroluminescence from silicon nanostructures heavily doped with boron

The circularly polarized electroluminescence (CPEL) from silicon nanostructures which are the p-type ultra-narrow silicon quantum well (Si-QW) confined by {\delta}-barriers heavily doped with boron, 5 10^21 cm^-3, is under study as a function of temperature and excitation levels. The CPEL dependences on the forward current and temperature show the circularly polarized light emission which appears to be caused by the exciton recombination through the negative-U dipole boron centers at the Si-QW {\delta}-barriers interface

Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices

The luminescence properties of highly strained, Sb-doped Ge/Si multi-layer heterostructures with incorporated Ge quantum dots (QDs) are studied. Calculations of the electronic band structure and luminescence measurements prove the existence of an electron miniband within the columns of the QDs. Miniband formation results in a conversion of the indirect to a quasi-direct excitons takes place. The optical transitions between electron states within the miniband and hole states within QDs are responsible for an intense luminescence in the 1.4–1.8 µm range, which is maintained up to room temperature. At 300 K, a light emitting diode based on such Ge/Si QD superlattices demonstrates an external quantum efficiency of 0.04% at a wavelength of 1.55 µm

Rabi oscillations as a tool to detect strong coupling of paramagnetic center with the nuclear spin bath

© 2019 Elsevier B.V. We show that strong coupling with the nuclear spin ensemble leaves an imprint on the nutation dynamics of the electron spin in the form of forced oscillations. The frequency of these oscillations equals Larmor precession frequency of the nuclear spins. This effect is evidenced by our experimental data on Rabi oscillations of paramagnetic nitroxyl radical TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) dispersed in glassy and crystalline ethanol. The data are interpreted in terms of a simple model that represents an impact of the proton spin bath as random local field with certain probability distribution. The electron spin coherence times of TEMPO in ethanol obtained by means of Hahn spin echo and Carr-Purcell-Meiboom-Gill sequences are compared with the calculations based on a spin diffusion model