Magnetism and Transport in Diluted Magnetic Semiconductor Quantum Dots

Authored by: Joaquín Fernández-Rossier , Ramon Aguado

Handbook of Spin Transport and Magnetism

Print publication date:  August  2011
Online publication date:  April  2016

Print ISBN: 9781439803776
eBook ISBN: 9781439803783
Adobe ISBN:

10.1201/b11086-36

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Abstract

The electronic spin already plays an important role in transport in quantum dots (QDs) made of nonmagnetic materials, like semiconductor, carbon nanotubes, and metallic grains. The standard experimental setup shown in Figure 30.1 consists of a central region, the QD, weakly coupled to two conducting electrodes, the source and drain. The charge of the dot is controlled by the electric field supplied by the gate voltage. We only consider situations where the charging energy of the dot, inversely proportional to its size, is larger than the temperature. In this Coulomb Blockade regime, the charge in the dot is quantized and whenever the highest energy electron is unpaired, the injection of an additional electron in the dot is only possible when its spin is opposite to that of the residing dot, because of the Pauli principle. At low temperature, these correlations result in the formation of the Kondo singlet, for which nontrivial spin correlations are established between the electron in the dot and those in the electrodes. Nontrivial spin effects in QD can also happen when the highest energy electrons reside a partially full degenerate shell. Other chapters of this book show how transport in magnetic materials attracts huge attention both for fundamental and applied perspectives. The influence of the magnetic state of the system over the electrical conduction gives rise to a variety of MR effects, like AMR in bulk materials, giant MR (GMR) in multilayers, tunneling MR (TMR) and AMR (TAMR) in tunnel junctions with magnetic electrodes, and so on. Conversely, the transport electrons can also affect the magnetic state of the system, through the so-called spin-transfer or spin-torque effect. Since both transport in magnetic materials and transport in nonmagnetic QDs results in very interesting spin-related phenomena, we expect that transport in dots made of magnetic materials leads to new fascinating physics. In this chapter, we focus on transport through QDs made of a fascinating class of magnetic materials, the so-called diluted magnetic semiconductors.

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