Electronic transport driven non-equilibrium phenomena in nanoelectronic, spintronic and thermoelectric systems

Lutfe A Siddiqui, Purdue University

Abstract

Electrons flowing through a material can interact with different degrees of freedom of their surrounding such as phonons, photons, plasmons, magnetization etc., which, although considered to remain in equilibrium in most electronic transport calculations, can be driven considerably far from equilibrium in nanoscale devices. Such effects can have different bearings on novel device design, ranging from performance degradation of novel nanoelectronic devices due to heating by non-equilibrium phonons, to conceptualization of novel spintronic devices based on controlling spin degrees of freedom (impurity spins, magnetization etc.) to, even, performance enhancement of thermoelectric devices by an increase in Seebeck coefficient due to non-equilibrium phonons. In this work we study a spectrum of such electronic transport driven non-equilibrium phenomena in a variety of experimental configurations. First, we show, while explaining experimental observations on suspended carbon nanotube quantum dots, that the radial breathing mode of a nanotube is driven into non-equilibrium by phonon-assisted electron tunneling mechanism. Second, we show, while explaining experiments on GaAs spin-valves with paramagnetic Mn impurities embedded inside the channel, that the impurity spins undergo a dynamical non-equilibrium spin-polarization due to spin-flip processes via conduction band electrons and also propose an electrically driven non-equilibrium magnetization scheme based on such effect. Third, we study an experimentally observed non-equilibrium ‘drag’ mechanism of phonons actuated by electrons flowing through a semiconductor and provide a model to evaluate its impact on thermoelectric device performance.

Degree

Ph.D.

Advisors

Datta, Purdue University.

Subject Area

Electrical engineering|Condensed matter physics|Materials science

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