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Recently, electrical injection of spin polarization in n-type and p-type silicon up to room-temperature has been experimentally carried out. Despite of these promising experimental results, a comprehensive theoretical framework concerning the influence of transport conditions on the spin depolarization process in silicon structures, in a wide range of values of temperature, doping concentration and amplitude of external fields, is still in a developing stage. In this contribution we use a semiclassical multiparticle Monte Carlo approach to simulate the electron transport and spin dynamics in lightly doped n-type Si crystals and numerically calculate the spin lifetimes of drifting electrons. Spin flipping is taken into account through the Elliot-Yafet mechanism, which is dominant in group IV materials. We discuss the influence of different intravalley and intervalley phonon interactions in the spin relaxation process during the spin transport. Our findings are in good agreement with those obtained by using different theoretical approaches. Moreover, our Monte Carlo predictions, in ranges of temperature and field amplitude yet unexplored, can guide future experimental studies towards a more effective design of room-temperature silicon based spintronic-devices. [ABSTRACT FROM AUTHOR]

The electron spin relaxation process in n-type GaAs crystals driven by a fluctuating electric field is investigated. Two different sources of fluctuations are considered: (i) a symmetric dichotomous noise and (ii) a Gaussian correlated noise. Monte Carlo numerical simulations show, in both cases, an enhancement of the spin relaxation time by increasing the amplitude of the external noise. Moreover, we find that the electron spin lifetime vs. the noise correlation time: (i) increases up to a plateau in the case of dichotomous random fluctuations, and (ii) shows a nonmonotonic behaviour with a maximum in the case of bulks subjected to a Gaussian correlated noise. [ABSTRACT FROM AUTHOR]

The effect of the addition of an external source of correlated noise on the electron transport in silicon MOS inversion layer, driven by a static electric field, has been investigated. The electron dynamics is simulated by a Monte Carlo procedure which takes into account non-polar optical and acoustic phonons. In our modelling of the quasi-two-dimensional electron gas, the potential profile, perpendicular to the MOS structure, is assumed to follow the triangular potential approximation. We calculate the changes in both the autocorrelation function and the spectral density of the velocity fluctuations, at different values of noise amplitude and correlation time. The findings indicate that, the presence of a fluctuating component added to the static electric field can affect the total noise power, i.e. the variance of the electron velocity fluctuations. Moreover, this effect critically depends on both the amplitude of the driving electric field and the noise parameters. [ABSTRACT FROM AUTHOR]

We investigate the electron spin dephasing in low n-doped GaAs semiconductor bulks driven by a correlated fluctuating electric field. The electron dynamics is simulated by a Monte Carlo procedure which keeps into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin relaxation times are computed through the D'yakonov-Perel process, which is the only relevant relaxation mechanism in zinc-blende semiconductors. The decay of initial spin polarization of conduction electrons is calculated for different values of field strength, noise intensity and noise correlation time. For values of noise correlation time comparable to the spin lifetime of the system, we find that spin relaxation times are significantly affected by the external noise. The effect increases with the noise amplitude. Moreover, for each value of the noise amplitude, a nonmonotonic behaviour of spin relaxation time as a function of the noise correlation time is found. [ABSTRACT FROM AUTHOR]

The influence of temperature and transport conditions on the electron spin relaxation in lightly doped n-type GaAs semiconductors is investigated. A Monte Carlo approach is used to simulate electron transport, including the evolution of spin polarization and relaxation, by taking into account intravalley and intervalley scattering phenomena of the hot electrons in the medium. Spin relaxation lengths and times are computed through the D'yakonov-Perel process, which is the more relevant spin relaxation mechanism in the regime of interest (10 < T < 300 K). The decay of the initial spin polarization of the conduction electrons is calculated as a function of the distance in the presence of a static electric field varying in the range 0.1-2 kV/cm. We find that the electron spin depolarization lengths and times have a nonmonotonic dependence on both the lattice temperature and the electric field amplitude. [ABSTRACT FROM AUTHOR]

A simulative study of cancer growth dynamics in patients affected by Chronic Myeloid Leukemia (CML), under the effect of a targeted dose-dependent continuous or pulsed therapy, is presented. We have developed a model for the dynamics of CML in which the stochastic evolution of white blood cell populations are simulated by adopting a Monte Carlo approach. Several scenarios in the evolutionary dynamics of white blood cells, as a consequence of the efficacy of the different modelled therapies, pulsed or continuous, are described. The best results, in terms of a permanent disappearance of the leukemic phenotype, are achieved with a continuous therapy and higher dosage. However, our findings demonstrate that an intermittent therapy could represent a valid choice in patients with high risk of toxicity, when a long-term therapy is considered. A suitably tuned pulsed therapy can enhance the treatment efficacy and reduce the percentage of patients developing resistance. [ABSTRACT FROM AUTHOR]

We study the effect of the impurity density on lifetimes and relaxation lengths of electron spins in the presence of a static electric field in an n-type GaAs bulk. The transport of electrons and the spin dynamics are simulated by using a semiclassical Monte Carlo approach, which takes into account the intravalley scattering mechanisms of warm electrons in the semiconductor material. Spin relaxation is considered through the D'yakonov-Perel mechanism, which is the dominant mechanism in III-V semiconductors. The evolution of spin polarization is analyzed by computing lifetimes and depolarization lengths as a function of the doping density in the range 1013 ÷ 5 × 1016 cm-3, for different values of the amplitude of the static electric field (0.1 ÷ 1.0 kV/cm). We find an increase of the electron spin lifetime as a function of the doping density, more evident for lattice temperatures lower than 150 K. Moreover, at very low intensities of the driving field, the spin depolarization length shows a nonmonotonic behaviour with the density. At the room temperature, spin lifetimes and depolarization lengths are nearly independent on the doping density. The underlying physics is analyzed. [ABSTRACT FROM AUTHOR]