arXiv subjects

E. Tutuc

Publications and source records attributed to E. Tutuc.

46 records · Page 3Linked to original sources

arXiv2003

In-Plane Magnetodrag between Dilute Two-Dimensional Systems

We performed in-plane magnetodrag measurements on dilute double layer two-dimensional hole systems, at in-plane magnetic fields that suppress the apparent metallic behavior, and to fields well above those required to fully spin polarize the system. When compared to the single layer magnetoresistance, the magnetodrag exhibits exactly the same qualitative behavior. In addition, we have found that the enhancement to the drag from the in-plane field exhibits a strong maximum when both layer densities are matched.

cond-mat.str-el↗

arXiv2003

Role of finite layer thickness in spin-polarization of GaAs 2D electrons in strong parallel magnetic fields

We report measurements and calculations of the spin-polarization, induced by a parallel magnetic field, of interacting, dilute, two-dimensional electron systems confined to GaAs/AlGaAs heterostructures. The results reveal the crucial role the non-zero electron layer thickness plays: it causes a deformation of the energy surface in the presence of a parallel field, leading to enhanced values for the effective mass and g-factor and a non-linear spin-polarization with field.

cond-mat.mes-hall↗

arXiv2002

Magnetic Field Induced Spin Polarization of AlAs Two-dimensional Electrons

Two-dimensional (2D) electrons in an in-plane magnetic field become fully spin polarized above a field B_P, which we can determine from the in-plane magnetoresistance. We perform such measurements in modulation-doped AlAs electron systems, and find that the field B_P increases approximately linearly with 2D electron density. These results imply that the product |g*|m*, where g* is the effective g-factor and m* the effective mass, is a constant essentially independent of density. While the deduced |g*|m* is enhanced relative to its band value by a factor of ~ 4, we see no indication of its divergence as 2D density approaches zero. These observations are at odds with results obtained in Si-MOSFETs, but qualitatively confirm spin polarization studies of 2D GaAs carriers.

cond-mat.mes-hall↗

arXiv2002

Valley splitting of AlAs two-dimensional electrons in a perpendicular magnetic field

By measuring the angles at which the Landau levels overlap in tilted magnetic fields (the coincidence method), we determine the splitting of the conduction-band valleys in high-mobility two-dimensional (2D) electrons confined to AlAs quantum wells. The data reveal that, while the valleys are nearly degenerate in the absence of magnetic field, they split as a function of perpendicular magnetic field. The splitting appears to depend primarily on the magnitude of the perpendicular component of the magnetic field, suggesting electron-electron interaction as its origin.

cond-mat.str-el↗

arXiv2002

Frictional Drag between Two Dilute Two-Dimensional Hole Layers

We report drag measurements on dilute double layer two-dimensional hole systems in the regime of r_s=19~39. We observed a strong enhancement of the drag over the simple Boltzmann calculations of Coulomb interaction, and deviations from the T^2 dependence which cannot be explained by phonon-mediated, plasmon-enhanced, or disorder-related processes. We suggest that this deviation results from interaction effects in the dilute regime.

cond-mat.mes-hall↗

arXiv2002

Spin polarization and transition from metallic to insulating behavior in 2D systems

We have made quantitative measurements of the spin polarization of two-dimensional (2D) GaAs (100) electrons and GaAs (311)A holes, as a function of an in-plane magnetic field. The functional form of the in-plane magnetoresistance is shown to be intimately related to the spin polarization. Moreover, for three different 2D systems, namely GaAs (100) electrons, GaAs (311)A holes, and AlAs (411)B electrons, the temperature dependence of the in-plane magnetoresistance reveals that their behavior turns from metallic to insulating before they are fully spin polarized.

cond-mat.mes-hall↗

arXiv2002

Spin polarization and g-factor of a dilute GaAs two-dimensional electron system

The effective g-factor ($g^{*}$) of a dilute interacting two-dimensional electron system is expected to increase with respect to its bare value as the density is lowered, and to eventually diverge as the system makes a transition to a ferromagnetic state. We report here measurements of $g^{*}$ in dilute (density 0.8 to 6.5 $\times10^{10}$cm$^{-2}$), high-mobility GaAs two-dimensional electrons from their spin polarization in a parallel magnetic field. The data reveal a surprising trend. While $g^{*}$ is indeed significantly enhanced with respect to the band g-factor of GaAs, the enhancement factor decreases from about 6 to 3 as the density is reduced.

cond-mat.mes-hall↗

arXiv2001

Anomalous Rashba spin splitting in two-dimensional hole systems

It has long been assumed that the inversion asymmetry-induced Rashba spin splitting in two-dimensional (2D) systems at zero magnetic field is proportional to the electric field that characterizes the inversion asymmetry of the confining potential. Here we demonstrate, both theoretically and experimentally, that 2D heavy hole systems in accumulation layer-like single heterostructures show the opposite behavior, i.e., a decreasing, but nonzero electric field results in an increasing Rashba coefficient.

cond-mat.mes-hall↗

arXiv2000

Resistance Spikes at Transitions between Quantum Hall Ferromagnets

We report a new manifestation of first-order magnetic transitions in two-dimensional electron systems. This phenomenon occurs in aluminum arsenide quantum wells with sufficiently low carrier densities and appears as a set of hysteretic spikes in the resistance of a sample placed in crossed parallel and perpendicular magnetic fields, each spike occurring at the transition between states with different partial magnetizations. Our experiments thus indicate that the presence of magnetic domains at the transition starkly increases dissipation, an effect also suspected in other ferromagnetic materials. Analysis of the positions of the transition spikes allows us to deduce the change in exchange-correlation energy across the magnetic transition, which in turn will help improve our understanding of metallic ferromagnetism.

cond-mat.mes-hall↗

arXiv2000

In-plane magnetic field-induced spin polarization and transition to insulating behavior in two-dimensional hole systems

Using a novel technique, we make quantitative measurements of the spin polarization of dilute (3.4 to 6.8*10^{10} cm^{-2}) GaAs (311)A two-dimensional holes as a function of an in-plane magnetic field. As the field is increased the system gradually becomes spin polarized, with the degree of spin polarization depending on the orientation of the field relative to the crystal axes. Moreover, the behavior of the system turns from metallic to insulating \textit{before} it is fully spin polarized. The minority-spin population at the transition is ~8*10^{9} cm^{-2}, close to the density below which the system makes a transition to an insulating state in the absence of a magnetic field.

cond-mat.mes-hall↗