Dilute Magnetic Semiconductors

Sinova, Jairo; Jungwirth, T.

doi:10.1007/3-540-27284-4_7

Cited by 10 publications

(6 citation statements)

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“…the dislocations themselves or other codoping, the ZT factor will be dominated exclusively by the 1D channels and a large ZT value can be obtained. 10 Below we present our theoretical estimate for this high ZT using reasonable estimates of the different parameters without seeking the best possible scenario but estimating instead a reasonable expectation of the proposed system.…”

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confidence: 99%

“…As more dislocations are introduced in the system the mean free path of the phonons is reduced while at the same time the conductivity contribution from the 1D channels is increased as mentioned above. By requiring that the bulk contribution is also reduced by Anderson localization of the bulk states, through the dislocations themselves or other co-doping, the ZT factor will be dominated exclusively by the 1D channels and a large ZT value can be obtained [16]. Below we present our theoretical estimate for this high ZT using reasonable estimates of the different parameters without seeking the best possible scenario but estimating instead a reasonable expectation of the proposed system.…”

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confidence: 99%

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Large thermoelectric figure of merit for three-dimensional topological Anderson insulators via line dislocation engineering

Tretiakov

Abanov

Murakami

et al. 2010

Applied Physics Letters

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We study the thermoelectric properties of three-dimensional topological Anderson insulators with line dislocations. We show that at high densities of dislocations the thermoelectric figure of merit ZT can be dominated by one-dimensional topologically protected conducting states channeled through the lattice screw dislocations in the topological insulator materials with a nonzero time-reversal-invariant momentum such as Bi 0.9 Sb 0.1 . When the chemical potential does not exceed much the mobility edge the ZT at room temperatures can reach large values, much higher than unity for reasonable parameters, hence making this system a strong candidate for applications in heat management of nanodevices.The recent crisis of heat management in nanodevices, which has lead to a lack of progression in clock speeds of charge-based logic devices, has intensified the interest in efficient thermoelectric materials. In the past decade there has been a lot of research both theoretical 1,2 and experimental 3,4 to create efficient thermoelectric nanodevices. Such materials must be both p-type and n-type. Their efficiency is determined by a balance to convert charge flow into efficient heat transport while maintaining a temperature gradient between the device and the heat sink. Among the most well known thermoelectric materials in present day commercial applications one finds Bi 2 Te 3 , PbTe, and PbSb. This type of insulators or semiconductors has been identified recently as topological insulators ͑TIs͒ ͑Ref. 5͒ which exhibit protected delocalized surface states.In the two-dimensional version of the TIs, the quantum spin Hall systems, 6,7 these protected edge states contribute to the thermoelectric efficiency but do not enhance it dramatically beyond present day materials whose efficiency parameter, ZT ͑see below͒, is of 1 or slightly less. 1 On the other hand, there are three-dimensional ͑3D͒ TIs with a nonzero time-reversal-invariant momentum 8 ͑TRIM͒. In these materials, it has been shown theoretically that one-dimensional ͑1D͒ topologically protected modes can exist in the bulk propagating through certain line dislocations. 9 Here we explore the idea of using these 1D topologically protected modes to significantly increase the thermoelectric efficiency of materials such as Bi 0.9 Sb 0.1 , see Fig. 1. The basic premise of the proposal is to introduce, through growth engineering, a finite density of screw dislocations. This would induce disorder in the bulk leading to a reduction of the thermal conductivity, Anderson localization of bulk states, and an increase of the conductivity and thermopower contributions from these 1D states. This combination of factors, as shown below, leads to a dramatic enhancement of the figure of merit efficiency for thermoelectrics, ZT, beyond its present value for bulk materials. For reasonable parameters we estimate ZT to reach ϳ6 at room temperature. Figure of merit. The performance of thermoelectric devices is determined by the dimensionless figure of merit ZT defined as ZT = S 2 T , ͑1͒where , S, , ...

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Large thermoelectric figure of merit for three-dimensional topological Anderson insulators via line dislocation engineering

Tretiakov

Abanov

Murakami

et al. 2010

Applied Physics Letters

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“…Several theoretical studies have recently considered the critical rotation of the gas, i.e. Ω ∼ ω ⊥ , which presents remarkable features [6,7,8,9,10,11,12,13,14]. From a classical point of view, for Ω = ω ⊥ the centrifugal force compensates the harmonic trapping force in the xy plane.…”

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“…Even though our picture properly describes the experiment, we are likely not to deal with the ground state of the system. On a very long time scale, the rotating gas can evolve to a more complex state, for instance to a multi-vortex state (with possible quantum melting) discussed in [6,8,11,12,13,14], or to a Quantum-Hall-like state [8,10]. However these states have been discussed for the axially symmetric case and a natural development will be to include a finite rotating anisotropy ǫ, which is a necessary ingredient for most present experiments.…”

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Critical Rotation of a Harmonically Trapped Bose Gas

et al. 2002

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We study experimentally and theoretically a cold trapped Bose gas under critical rotation, i.e., with a rotation frequency close to the frequency of the radial confinement. We identify two regimes: the regime of explosion where the cloud expands to infinity in one direction, and the regime where the condensate spirals out of the trap as a rigid body. The former is realized for a dilute cloud, and the latter for a condensate with the interparticle interaction exceeding a critical value. This constitutes a novel system in which repulsive interactions help in maintaining particles together.

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“…Within this model and its variants, the magnitude of the Curie temperature T C in Mn--doped GaAs, InAs, GaSb, InSb [4][5][6] as well as in p-CdTe, p-ZnTe, and Ge [7] is understood assuming that the long-range ferromagnetic interactions between the localised spins are mediated by delocalised holes in the weakly perturbed valence band [8]. The assumption that the relevant carriers reside in the p-like valence band makes it possible to describe various magnetooptical [4,9] and magnetotransport properties of (Ga,Mn)As, including the anomalous Hall effect and anisotropic magnetoresistance [9,10] as well the negative magnetoresistance caused by the orbital weak-localisation effect [11]. From this point of view, (Ga,Mn)As and related compounds emerge as the best understood ferromagnets, providing a basis for the development of novel methods enabling magnetisation manipulation and switching [12].…”

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Magnetic Properties of (Ga,Mn)As

Sawicki

2004

Acta Phys. Pol. A

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A review is given of experimental findings and theoretical understanding of micromagnetic properties of zinc-blende ferromagnetic semiconductors, with (Ga,Mn)As taken as a sole example. It is emphasised that the Zener p−d model explains quantitatively the effect of strain on the easy axis direction as well as it predicts correctly the presence of the reorientation transition, observed as a function of hole concentration and temperature. Possible suggestions put forward to explain the existence of in-plane uniaxial magnetocrystalline anisotropy are then quoted.

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Dilute Magnetic Semiconductors

Cited by 10 publications

References 98 publications

Large thermoelectric figure of merit for three-dimensional topological Anderson insulators via line dislocation engineering

Large thermoelectric figure of merit for three-dimensional topological Anderson insulators via line dislocation engineering

Critical Rotation of a Harmonically Trapped Bose Gas

Magnetic Properties of (Ga,Mn)As

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