Microscopic derivation of transport coefficients and boundary conditions in discrete drift-diffusion models of weakly coupled superlattices

Bonilla, Luis L.; Platero, Gloria; Sánchez, David

doi:10.1103/physrevb.62.2786

Cited by 48 publications

(107 citation statements)

References 34 publications

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“…More sophisticated models 36,37 have proven that a proper description of the contacts can have a strong effect on the selection of the the transport equation solution when multistability occurs, especially when dynamical solutions are allowed. 37 However, we choose not to delve into these effects in detail here since our main interest is on spin effects. For the sake of definiteness, the contacts are taken to be unpolarized throughout our calculations; including spin-polarized injection in our theory would be straightforward and indeed this may be a very interesting avenue to explore in future experimental and theoretical studies.…”

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Field-domain spintronics in magnetic semiconductor multiple quantum wells

2001

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We develop a theory of non-linear growth direction transport in magnetically doped II-VI compound semiconductor multiple-quantum-well systems. We find that the formation of electric field domains can be controlled by manipulating the space dependence of the band electron spin-polarization, using its exchange coupling to local moments. We emphasize the importance of band electron spin relaxation in limiting the strength of these effects.72.25. Dc, 72.25.Mk, 73.21.Cd, 75.50.Pp

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Field-domain spintronics in magnetic semiconductor multiple quantum wells

2001

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“…͑10͒ after imposing n i ϭn iϩ1 ϭN w and setting an average interwell electric field F along the SL period Lϭdϩw. 31 In what follows, we neglect the contribution from diffusivity, which can be important at very low electric fields. 31 As shown in Ref.…”

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“…,N, where N is the number of wells, supplemented with Poisson equations, constitutive relations, and realistic boundary conditions. 26,31 In the following paragraphs, we shall elaborate on this.…”

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Dynamical instability of electric-field domains in ac-driven superlattices

2003

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We analyze theoretically the dynamical transport through a weakly coupled semiconductor superlattice, under an ac potential with frequencies in the THz regime, by means of a general model for time-dependent sequential tunneling within a nonequilibrium-Green's-function framework. Highly doped superlattices present, under certain conditions, the formation of electric-field domains at a static dc voltage bias. We find that the THz signal drives the system from a stationary current toward an oscillatory time dependence as the ac intensity increases. However, the current oscillates periodically in the MHz regime, reflecting an ac-induced motion and recycling of traveling domain walls. Finally, we predict that on further increasing the intensity of the ac potential, the tunneling current undergoes a transition from a periodically time-dependent state to a stationary one in which a homogeneous electric-field distribution builds up along the sample.

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“…11 Its form is assumed to be the same as in the 2D case ͑see also discussion below͒. 1,12 We define t tun ϭL/v(⌬⌽ peak ) and the dimensionless time as ϭt/t tun . We define VϭV/⌬⌽ peak (Nϩ1) as the dc bias amplitude between two unit cells.…”

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Chaotic transport in low-dimensional superlattices

2003

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We predict that in arrays of quantum dots ͑0D superlattice͒ and arrays of one-dimensional quantum wires ͑1D superlattice͒ chaotic transport should be observed in the presence of an ac field and for a wide range of physical parameters, like the external dc bias, contact charge, doping levels, and disorder in the array. Timedependent current oscillations set in the array due to the formation of electric domain walls when sequential resonant tunneling is the main transport mechanism between adjacent units. Such oscillations can then be forced into spatiotemporal chaos. A similar phenomenon has been predicted and demonstrated for solid-state superlattices. However, contrary to the latter case, the domain walls move across a larger number of units in the superlattice the lower the dimensionality, due to the different spatial distribution of the electric-field across the array in the three cases. Chaotic transport in GaAs/AlAs superlattices has been theoretically predicted 1 and experimentally demonstrated 2 a few years ago. It was found that, when the main charge transport mechanism is sequential resonant tunneling between adjacent quantum wells, undamped time-dependent oscillations of the current appear. 3 Such oscillations are due to the motion and recycling of electric field and charge domain walls in the superlattice. 1 Due to the presence of such natural oscillations, spatiotemporal chaos can be induced by a suitable external oscillating field. 1,4 In recent years, new type of nanostructures, like, e.g., nanotubes, molecular or atomic wires ͑often globally referred to as quantum wires͒, have received considerable attention in view of their possible use as components in future electronic applications. 5 While much of the research has focused so far on the new transport issues that arise in single quantum wires, less work has been devoted to the study of transport properties of arrays of quantum wires. The latter systems constitute a natural step towards integration of nanoscale components into functional devices. Since such systems represent an extension of the well-known concept of two-dimensional ͑2D͒ solid-state superlattices 6 and sequential resonant tunneling can be the main transport mechanism in such structures, it is natural to ask if ͑i͒ natural oscillations can be observed in superlattices with even lower dimansionality, and, consequently, ͑ii͒ such oscillations can be forced into spatiotemporal chaos by an appropriate oscillating field.In this paper, we show that the answer to both questions is positive. In particular, we examine arrays of quantum dots ͑0D superlattice͒ and arrays of one-dimensional quantum wires ͑1D superlattice͒. By array of quantum wires we mean either a finite series of zero dimensional ͑0D͒ structures ͓see Fig. 1͑a͔͒ or a series of one dimensional ͑1D͒ structures ͓Fig. 1͑b͔͒ between two bulk electrodes. The 0D superlattice can be made of, for instance, a series of weakly coupled molecules, 7 or a series of nanowire units, 8 and the 1D superlattice a series of, say, nanotubes. 5 We...

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Microscopic derivation of transport coefficients and boundary conditions in discrete drift-diffusion models of weakly coupled superlattices

Cited by 48 publications

References 34 publications

Field-domain spintronics in magnetic semiconductor multiple quantum wells

Field-domain spintronics in magnetic semiconductor multiple quantum wells

Dynamical instability of electric-field domains in ac-driven superlattices

Chaotic transport in low-dimensional superlattices

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