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Register a new userDetermination of $g$-factor in InAs two-dimensional electron system by capacitance spectroscopy
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We determine the effective $g$-factor ($|g^ast|$) of a two-dimensional electron gas (2DEG) using a new method based on capacitance spectroscopy. The capacitance-voltage profile of a 2DEG in an InAs/AlGaSb quantum well measured in an in-plane magnetic field shows a double-step feature that indicates the Zeeman splitting of the subband edge. The method allows for simultaneous and independent determination of $|g^ast|$ and effective mass $m^ast$. Data suggest that the biaxial tensile strain in the InAs layer has considerable impacts on both $m^ast$ and $g^ast$. Our method provides a means to determine $|g^ast|$ that is complementary to the commonly used coincidence technique.
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Photoluminescence data from single, self-assembled InAs/InP quantum dots in magnetic fields up to 7 T are presented. Exciton g-factors are obtained for dots of varying height, corresponding to ground state emission energies ranging from 780 meV to 1100 meV. A monotonic increase of the g-factor from -2 to +1.2 is observed as the dot height decreases. The trend is well reproduced by sp3 tight binding calculations, which show that the hole g-factor is sensitive to confinement effects through orbital angular momentum mixing between the light-hole and heavy-hole valence bands. We demonstrate tunability of the exciton g-factor by manipulating the quantum dot dimensions using pyramidal InP nanotemplates.
We present a method to create spin-polarized beams of ballistic electrons in a two-dimensional electron system in the presence of spin-orbit interaction. Scattering of a spin-unpolarized injected beam from a lithographic barrier leads to the creation of two fully spin-polarized side beams, in addition to an unpolarized specularly reflected beam. Experimental magnetotransport data on InSb/InAlSb heterostructures demonstrate the spin-polarized reflection in a mesoscopic geometry, and confirm our theoretical predictions.
The lifting of the two-fold degeneracy of the conduction valleys in a strained silicon quantum well is critical for spin quantum computing. Here, we obtain an accurate measurement of the splitting of the valley states in the low-field region of interest, using the microwave spectroscopy technique of electron valley resonance (EVR). We compare our results with conventional methods, observing a linear magnetic field dependence of the valley splitting, and a strong low-field suppression, consistent with recent theory. The resonance linewidth shows a marked enhancement above $Tsimeq 300$ mK.
Positive signs of the effective g-factors for free electrons in the conduction band and electrons localized on deep paramagnetic centers have been measured in nitrogen dilute alloy GaAs{0.979}N{0.021} at room temperature. The g-factor signs have been determined from an asymmetry in the depolarization of edge photoluminescence in a transverse magnetic field (Hanle effect) at the oblique incidence of the exciting radiation and oblique-angle detection of the luminescence. The tilted spin polarization of free electrons is induced under interband absorption of circularly polarized light, and the paramagnetic centers acquire spin polarization because of spin-dependent capture of free spin-polarized electrons by these centers. The measured Hanle curve is a superposition of two lines, narrow and broad, with the widths ~400 G and ~50000 G, arising due to the depolarization of localized and free electrons, respectively. The magnitude and direction of the asymmetry in the measured Hanle curve have been found to depend on the partial contributions to the photoluminecsence from the heavy- and light-hole subbands split by a uniaxial deformation of the GaAs{1-x}N{x} film grown on a GaAs substrate. We have extended the theory of optical orientation in order to calculate the excitation spectrum of the photoelectron tilted-spin polarization and the circularly-polarized luminescence spectrum taking into account that, in the strained samples under study, the light-hole subband lies above the heavy-hole one. The results have further been used to calculate the shape of Hanle curve as a function of the excitation and registration energies as well as the incidence and detection angles and to compare the theory with experiment.
We have determined the Lande factor g* in self-organized InAs quantum dots using resonant-tunnelling experiments. With the magnetic field applied parallel to the growth direction z we find g*_parallel = 0.75 for the specific dot investigated. When the magnetic field is tilted away by theta from the growth axis, g* gradually increases up to a value g*_perp = 0.92 when B perp z. Its angular dependence is found to follow the phenomenological behaviour g* (theta) = sqrt{(g*_parallel cos(theta)^2 + (g*_perp sin(theta)^2}.
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