Author: Alex Randall Hodges
Publisher:
ISBN:
Category :
Languages : en
Pages :
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We use time-resolved magneto-photoluminescence spectroscopy to study spin relaxation of excitons in a series of strained and unstrained ZnMnSe-based heterostructures. In an unstrained ZnMnSe epilayer, we find rapid spin relaxation, with a spin relaxation time of less than five picoseconds. We attribute this rapid spin relaxation to the complicated band structure: the various exciton spin bands intersect each other numerous times. The excitons can freely scatter between the spin bands, resulting in rapid spin relaxation. In contrast, we find extremely slow spin relaxation in a strained ZnMnSe/ZnFeSe multiple quantum well, with a spin relaxation time of greater than one nanosecond. Once excitons cool to the bottom of the band, very little spin relaxation occurs, and an extremely non-thermal exciton spin distribution persists throughout the lifetime of the exciton. In addition, we show that the dominant spin relaxation mechanism in this structure is LO-phonon emission during the momentum relaxation process, which occurs within 1 ps of the exciting laser pulse. We find similar results in two additional strained structures. For a strained ZnMnSe epilayer and a strained ZnMnSe/ZnSe multiple quantum well, we also see very slow spin relaxation, with spin relaxation times of greater than 1 ns. We conclude that this effect is due to the removal of the light hole - heavy hole valence band degeneracy by the lattice strain. This eliminates the band-mixing effects that lead to rapid spin relaxation in unstrained ZnMnSe-based heterostructures, thus resulting in extremely slow spin relaxation. We also find that the addition of a small fraction of cadmium to a strained quantum well strongly increases the spin relaxation rate. In a strained ZnCdMnSe/ZnSe quantum well, we see rapid spin relaxation, with a spin relaxation time of less than 5 ps, similar to that of the unstrained ZnMnSe epilayer. However, as in the other strained structures, the excitons spins never fully thermalize with the lattice. The spin relaxation, while initially rapid, is incomplete.
Author: Christian D. Poweleit
Publisher:
ISBN:
Category :
Languages : en
Pages : 322
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Author: Evgeny Y. Tsymbal
Publisher: CRC Press
ISBN: 0429784384
Category : Science
Languages : en
Pages : 619
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Book Description
The second edition offers an update on the single most comprehensive survey of the two intertwined fields of spintronics and magnetism, covering the diverse array of materials and structures, including silicon, organic semiconductors, carbon nanotubes, graphene, and engineered nanostructures. It focuses on seminal pioneering work, together with the latest in cutting-edge advances, notably extended discussion of two-dimensional materials beyond graphene, topological insulators, skyrmions, and molecular spintronics. The main sections cover physical phenomena, spin-dependent tunneling, control of spin and magnetism in semiconductors, and spin-based applications.
Author: Matthew D. Mower
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 113
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Book Description
Spintronics has the potential to play a significant role in future electronic devices. The success of the field hinges on our ability to maintain and propagate spin signals over various length scales and periods of time. Common to all devices designed to carry spin signals is a need to hold the spin orientation of constituent particles, individually or in bulk. Spin relaxation is a measure of how long particle spins remain polarized while subjected to both spin-dependent and spin-independent interactions. An effect typically driven by the spin-orbit interaction in semiconductors, spin relaxation describes the rate at which spin polarized particles return to an equilibrium spin distribution. This is generally in competition with the goals of spintronic devices which generate out-of-equilibrium spin populations to represent signals. By studying the various mechanisms of spin relaxation in different systems, we learn which materials are appropriate for specific applications and get hints about how to minimize signal loss. This report focuses largely on Dyakonov-Perel spin relaxation of carriers in III-V semiconductors. Of the spin relaxation mechanisms in III-V semiconductors, Dyakonov-Perel often dominates or is at least a primary contributor. We study the mechanism in detail for both non-magnetic and dilute magnetic semiconductors, deriving analytic expressions that include contributions from many-body interactions. The results shed light on the validity of commonly made approximations in calculating spin relaxation for various systems. More importantly, we show how spin relaxation can affect other physical observables, such as spin diffusion. By investigating this spin relaxation mechanism in a dilute magnetic semiconductor, we include the effects of spin-dependent interactions. These interactions result in some peculiarities of spin relaxation for carriers undergoing a ferromagnetic transition.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 652
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Author: Jan A. Gaj
Publisher: Springer Science & Business Media
ISBN: 3642158560
Category : Science
Languages : en
Pages : 484
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Book Description
As materials whose semiconducting properties are influenced by magnetic ions, DMSs are central to the emerging field of spintronics. This volume focuses both on basic physical mechanisms (e.g. carrier-ion and ion-ion interactions), and resulting phenomena.
Author: David Abraham Tulchinsky
Publisher:
ISBN:
Category :
Languages : en
Pages : 164
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Author: American Ceramic Society
Publisher:
ISBN:
Category : Ceramics
Languages : en
Pages : 1150
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Book Description
Author: Marcin L. Sadowski
Publisher: Springer Science & Business Media
ISBN: 9780792363163
Category : Science
Languages : en
Pages : 470
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Book Description
Optical methods for investigating semiconductors and the theoretical description of optical processes have always been an important part of semiconductor physics. Only the emphasis placed on different materials changes with time. Here, a large number of papers are devoted to quantum dots, presenting the theory, spectroscopic investigation and methods of producing such structures. Another major part of the book reflects the growing interest in diluted semiconductors and II-IV nanosystems in general. There are also discussions of the fascinating field of photonic crystals. `Classical' low dimensional systems, such as GsAs/GaAlAs quantum wells and heterostructures, still make up a significant part of the results presented, and they also serve as model systems for new phenomena. New materials are being sought, and new experimental techniques are coming on stream, in particular the combination of different spectroscopic modalities.
Author:
Publisher:
ISBN:
Category : Semiconductors
Languages : en
Pages : 534
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Book Description
