Electrong-factor anisotropy in symmetric (110)-oriented GaAs quantum wells

Abstract

We demonstrate by spin quantum beat spectroscopy that in undoped symmetric (110)-oriented GaAs/AlGaAs single quantum wells even a symmetric spatial envelope wavefunction gives rise to an asymmetric in-plane electron Landé-g-factor. The anisotropy is neither a direct consequence of the asymmetric in-plane Dresselhaus splitting nor of the asymmetric Zeeman splitting of the hole bands but is a pure higher order effect that exists as well for diamond type lattices. The measurements for various well widths are very well described within 14 × 14 band k · p theory and illustrate that the electron spin is an excellent meter variable to map out the internal -otherwise hidden-symmetries in two dimensional systems. Fourth order perturbation theory yields an analytical expression for the strength of the g-factor anisotropy, providing a qualitative understanding of the observed effects.PACS numbers: 78.55. Cr,78.47.jd,78.20.Ci,71.18.+y Symmetry is a fundamental principle which runs through all fields of sciences like a common thread. The balance of proportions is attracting great interest ever since reaching from Euclid's geometry theorems and the Archimedes lever principle in ancient times to Mandelbrot sets in present day mathematics and parity violation in modern particle physics. At the beginning of the last century the topic was significantly pushed by Emmy Noether's discovery of the deep connection between symmetry and conservation laws [1] and the classification of nearly all entities in today's physics in terms of its symmetry properties is a very powerful and widely applied method in a vast number of fields. Among the plethora of interesting physical observables the pure quantum mechanical entity spin in connection with the relativistic effect of spin-orbit interaction (SOI) [2] bears an exceeding connection to symmetry. In a free atom, SOI can break the degeneracy of states with the same orbital wave function owing opposite spins. In solids, however, such a splitting interferes with crystal symmetry. The most prominent example is the conduction band Dresselhaus splitting in zinc-blende (ZB) type lattice semiconductors [3], which is not present in their diamond lattice type equivalents [4]. The alteration of the symmetry allows a clear assignment of the investigated spin properties to the symmetry at hand and the change of symmetry properties on micro-and macroscopic scales is easy to produce in solid state physics by the introduction of low dimensional structures, potential gradients, or the choice of peculiar crystallographic quantization axes. This fact has boosted a great interest in recent semiconductor spintronic research [5][6][7] since crystal symmetry yields a control on the spin dynamics [8][9][10][11][12] and contrariwise the entity spin yields jointly with the time-reversal breaking property of a magnetic a unique meter variable to probe internal symmetries which might be inaccessible by other means.In this letter, we exploit the intriguing property that quantum wells (QW) grown with their quantizatio...

Effect of symmetry reduction on the spin dynamics of (001)-oriented GaAs quantum wells

“…(5) for larger confinement energy and hence lower potential gradient. 22 The strength of the Rashba term α is mediated by the asymmetry of the wave function which is larger for wider quantum wells for a given potential gradient. The value of β is proportional to the confinement energy and is therefore larger for the 10 nm well than the 17.5 nm well and decreases for increasing potential gradient.…”

“…As demonstrated by Kalevich and Korenev, these corrections introduce off-diagonal elements into the g factor tensor, which therefore has three independent components, i.e., g xx = g yy , g zz , and g xy = g yx = 0. 13 This yields an in-plane anisotropy of the g factor which is given by 10,13,22 …”

Nonlinear spin Hall effect in GaAs (110) quantum wells

“…This is related to the expectation of the longest spin relaxation times in these structures, [9][10][11][12][13][14][15][16] which in turn can lead to interesting spin dynamics. 17,18 A stationary pure spin current accompanying an electric current in (110) QWs was observed as reported in Ref. [19].…”

Strain-induced spin relaxation anisotropy in symmetric (001)-oriented GaAs quantum wells

“…The reduction of the symmetry to C 2v allows in-plane anisotropy of the g factor, which can be specified by nonzero off-diagonal elements of the g tensor, 25,28 g xy = g yx = 0. Thus,…”

“…However, the observed anisotropy and its strength depend on the microscopic mechanisms involved. 25 In the case of s ⊥ , the application of strain induces an STR component of the spin-splitting vector, which interferes with the intrinsic BIA component and generates the anisotropy. This is exactly analogous to the interference of SIA and BIA components for an applied electric field, as predicted originally by Averkiev and Golub.…”