Igor Žutić

Proposal for a spin-polarized solar battery

A solar cell illuminated by circularly polarized light generates charge and spin currents. We show that the spin polarization of the current significantly exceeds the spin polarization of the carrier density for the majority carriers. Based on this principle, we propose a semiconductor spin-polarized solar battery and substantiate our proposal using analytical arguments and numerical modeling.

Bipolar spintronics: fundamentals and applications

By incorporating spin-dependent properties and magnetism in semiconductor structures, new applications can be considered which go beyond magnetoresistive effects in metallic systems. Notwithstanding the prospects for spin/magnetism-enhanced logic in semiconductors, many important theoretical, experimental, and materials challenges remain. Here we discuss the challenges for realizing a particular class of associated applications and our proposal for bipolar spintronic devices in which carriers of both polarities (electrons and holes) would contribute to spin-charge coupling. We formulate the theoretical framework for bipolar spin-polarized transport and describe several novel effects in two-and three-terminal structures which arise from the interplay between nonequilibrium spin and equilibrium magnetization.

Analytical model of spin-polarized semiconductor lasers

We formulate an analytical model for semiconductor lasers with injection (pump) of spin-polarized electrons, allowing us to systematically investigate different operating regimes. We demonstrate that the maximum threshold reduction by electrically pumped spin-polarized carriers is larger than previously thought possible and, surprisingly, can be enhanced by ultrafast spin relaxation of holes. We reveal how different modes of carrier recombination directly affect the threshold reduction. Neither spin-up nor spin-down electron populations are separately clamped (pinned) near the threshold, where such lasers can act as effective nonlinear filters of circularly polarized light, owing to their spin-dependent gain.

Spintronics: Silicon twists

For decades, silicon has been the dominant material for conventional, charge-based electronics. A new twist makes silicon ripe to enter the domain of spintronics, where the new currency is electron spin.

Bipolar spintronics: from spin injection to spin-controlled logic

An impressive success of spintronic applications has been typically realized in metal-based structures which utilize magnetoresistive effects for substantial improvements in the performance of computer hard drives and magnetic random access memories. Correspondingly, the theoretical understanding of spinpolarized transport is usually limited to a metallic regime in a linear response, which, while providing a good description for data storage and magnetic memory devices, is not sufficient for signal processing and digital logic. In contrast, much less is known about possible applications of semiconductorbased spintronics and spin-polarized transport in related structures which could utilize strong intrinsic nonlinearities in current‐voltage characteristics to implement spin-based logic. Here we discuss the challenges for realizing a particular class of structures in semiconductor spintronics: our proposal for bipolar spintronic devices in which carriers of both polarities (electrons and holes) contribute to spin-charge coupling. We formulate the theoretical framework for bipolar spin-polarized transport, and describe several novel effects in two- and three-terminal structures which arise from the interplay between nonequilibrium spin and equilibrium magnetization. (Some figures in this article are in colour only in the electronic version)

Electronic states of magnetic quantum dots

We study quantum states of electrons in magnetically doped quantum dots as a function of exchange coupling between electron and impurity spins, the strength of Coulomb interaction, confining potential and the number of electrons. The magnetic phase diagram of quantum dots, doped with a large number of magnetic Mn impurities, can be described by the energy-gap in the spectrum of electrons and the mean field electron–Mn exchange coupling. A competition between these two parameters leads to a transition between spin-unpolarized and spin-polarized states, in the absence of applied magnetic field. Tuning the energy-gap by electrostatic control of nonparabolicity of the confining potential can enable control of magnetization even at the fixed number of electrons. We illustrate our findings by directly comparing Mn-doped quantum dots with parabolic and Gaussian confining potential.

Spintronics: Shedding light on nanomagnets.

The magnetism of semiconductor nanocrystals can be controlled by shining light on them, which could have applications in information storage and processing.

Magnetic anisotropies of quantum dots doped with magnetic ions

Magnetic anisotropies in quantum dots (QDs) doped with magnetic ions are discussed in terms of two frameworks: anisotropic

Superconducting proximity effects in metals with a repulsive pairing interaction

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Spin Twists in a Transistor

-factors and magnetocrystalline anisotropy energy. It is shown that even a simple model of zinc-blende p-doped QDs displays a rich diagram of magnetic anisotropies in the QD parameter space. Tuning the confinement allows to control magnetic easy axes in QDs in ways not available for the better-studied bulk.