Weak antilocalization in a 2D electron gas with the chiral splitting of the spectrum

Motivated by the recent observation of the metal-insulator transition in Si-MOSFETs we consider the quantum interference correction to the conductivity in the presence of the Rashba spin splitting. For a small splitting, a crossover from the localizing to antilocalizing regime is obtained. The symplectic correction is revealed in the limit of a large separation between the chiral branches. The relevance of the chiral splitting for the 2D electron gas in Si-MOSFETs is discussed.Comment: 7 pages, REVTeX. Mistake corrected; in the limit of a large chiral splitting the correction to the conductivity does not vanish but approaches the symplectic valu

On the problem of catastrophic relaxation in superfluid 3-He-B

In this Letter we discussed the parametric instability of texture of homogeneous (in time) spin precession, explaining how spatial inhomogeneity of the texture may change the threshold of the instability in comparison with idealized spatial homogeneous case, considered in our JETP Letter \textbf{83}, 530 (2006), cond-mat/0605386. This discussion is inspired by critical Comment of I.A. Fomin (cond-mat/0606760) related to the above questions. In addition we considered here results of direct numerical simulations of the full Leggett-Takagi equation of motion for magnetization in superfluid 3He-B and experimental data for magnetic field dependence of the catastrophic relaxation, that provide solid support of the theory of this phenomenon, presented in our 2006 JETP Letter.Comment: 5 pages, 1 fig. included, JETP Lett. style, submitted to JETP Lett. as response to Comment cond-mat/060676

Solution of the problem of catastrophic relaxation of homogeneous spin precession in superfluid 3^3He-B

The quantitative analysis of the "catastrophic relaxation" of the coherent spin precession in $^3$He-B is presented. This phenomenon has been observed below the temperature about 0.5 T$_c$ as an abrupt shortening of the induction signal decay. It is explained in terms of the decay instability of homogeneous transverse NMR mode into spin waves of the longitudinal NMR. Recently the cross interaction amplitude between the two modes has been calculated by Sourovtsev and Fomin \cite{SF} for the so-called Brinkman-Smith configuration, i.e. for the orientation of the orbital momentum of Cooper pairs along the magnetic field, ${\bf L}\parallel {\bf H}$. In their treatment, the interaction is caused by the anisotropy of the speed of the spin waves. We found that in the more general case of the non-parallel orientation of ${\bf L}$ corresponding to the typical conditions of experiment, the spin-orbital interaction provides the additional interaction between the modes. By analyzing experimental data we are able to distinguish which contribution is dominating in different regimes.Comment: 6 pages, 1 figure, submited to JETP letter

Orbital mechanism of the circular photogalvanic effect in quantum wells

It is shown that the free-carrier (Drude) absorption of circularly polarized radiation in quantum well structures leads to an electric current flow. The photocurrent reverses its direction upon switching the light helicity. A pure orbital mechanism of such a circular photogalvanic effect is proposed that is based on interference of different pathways contributing to the light absorption. Calculation shows that the magnitude of the helicity dependent photocurrent in $n$-doped quantum well structures corresponds to recent experimental observations.Comment: 5 pages, 2 figures, to be published in JETP Letter

Zero-Field Satellites of a Zero-Bias Anomaly

Spin-orbit (SO) splitting, $\pm \omega_{SO}$, of the electron Fermi surface in two-dimensional systems manifests itself in the interaction-induced corrections to the tunneling density of states, $\nu (\epsilon)$. Namely, in the case of a smooth disorder, it gives rise to the satellites of a zero-bias anomaly at energies $\epsilon=\pm 2\omega_{SO}$. Zeeman splitting, $\pm \omega_{Z}$, in a weak parallel magnetic field causes a narrow {\em plateau} of a width $\delta\epsilon=2\omega_{Z}$ at the top of each sharp satellite peak. As $\omega_{Z}$ exceeds $\omega_{SO}$, the SO satellites cross over to the conventional narrow maxima at $\epsilon = \pm 2\omega_{Z}$ with SO-induced plateaus $\delta\epsilon=2\omega_{SO}$ at the tops.Comment: 7 pages including 2 figure

Berry phase and adiabaticity of a spin diffusing in a non-uniform magnetic field

An electron spin moving adiabatically in a strong, spatially non-uniform magnetic field accumulates a geometric phase or Berry phase, which might be observable as a conductance oscillation in a mesoscopic ring. Two contradicting theories exist for how strong the magnetic field should be to ensure adiabaticity if the motion is diffusive. To resolve this controversy, we study the effect of a non-uniform magnetic field on the spin polarization and on the weak-localization effect. The diffusion equation for the Cooperon is solved exactly. Adiabaticity requires that the spin-precession time is short compared to the elastic scattering time - it is not sufficient that it is short compared to the diffusion time around the ring. This strong condition severely complicates the experimental observation.Comment: 16 pages REVTEX, including 3 figure

Conduction band spin splitting and negative magnetoresistance in A3B5{\rm A}_3{\rm B}_5 heterostructures

The quantum interference corrections to the conductivity are calculated for an electron gas in asymmetric quantum wells in a magnetic field. The theory takes into account two different types of the spin splitting of the conduction band: the Dresselhaus terms, both linear and cubic in the wave vector, and the Rashba term, linear in wave vector. It is shown that the contributions of these terms into magnetoconductivity are not additive, as it was traditionally assumed. While the contributions of all terms of the conduction band splitting into the D'yakonov--Perel' spin relaxation rate are additive, in the conductivity the two linear terms cancel each other, and, when they are equal, in the absence of the cubic terms the conduction band spin splitting does not show up in the magnetoconductivity at all. The theory agrees very well with experimental results and enables one to determine experimentally parameters of the spin-orbit splitting of the conduction band.Comment: 8 pages, RevTeX, 4 Postscript figure

Hall-like effect induced by spin-orbit interaction

The effect of spin-orbit interaction on electron transport properties of a cross-junction structure is studied. It is shown that it results in spin polarization of left and right outgoing electron waves. Consequently, incoming electron wave of a proper polarization induces voltage drop perpendicularly to the direct current flow between source and drain of the considered four-terminal cross-structure. The resulting Hall-like resistance is estimated to be of the order of 10^-3 - 10^-2 h/e^2 for technologically available structures. The effect becomes more pronounced in the vicinity of resonances where Hall-like resistance changes its sign as function of the Fermi energy.Comment: 4 pages (RevTeX), 4 figures, will appear in Phys. Rev. Let

Experimental study of weak antilocalization effect in a high mobility InGaAs/InP quantum well

The magnetoresistance associated with quantum interference corrections in a high mobility, gated InGaAs/InP quantum well structure is studied as a function of temperature, gate voltage, and angle of the tilted magnetic field. Particular attention is paid to the experimental extraction of phase-breaking and spin-orbit scattering times when weak anti- localization effects are prominent. Compared with metals and low mobility semiconductors the characteristic magnetic field $B_{tr} = \hbar/4eD \tau$ in high mobility samples is very small and the experimental dependencies of the interference effects extend to fields several hundreds of times larger. Fitting experimental results under these conditions therefore requires theories valid for arbitrary magnetic field. It was found, however, that such a theory was unable to fit the experimental data without introducing an extra, empirical, scale factor of about 2. Measurements in tilted magnetic fields and as a function of temperature established that both the weak localization and the weak anti-localization effects have the same, orbital origin. Fits to the data confirmed that the width of the low field feature, whether a weak localization or a weak anti-localization peak, is determined by the phase-breaking time and also established that the universal (negative) magnetoresistance observed in the high field limit is associated with a temperature independent spin-orbit scattering time.Comment: 13 pages including 10 figure