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

Abstract

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.

Photon-assisted transport in semiconductor nanostructures

“…The way an external high frequency field affects this complex dynamics has been analyzed in Ref. [169] by using the non-equilibrium Green's function formalism described Section 5. It is straightforward to generalize the derivation of the time dependent current in Section 5, see Eqs.…”

Non-linear dynamics of semiconductor superlattices

“…Photo-assisted dynamical transport in highly doped, weakly coupled SLs and its consequences for EFD formation were theoretically investigated by López et al [280,281]. The results indicate that the terahertz field induces with increasing intensity a transition from a stationary configuration to a dynamic state with an ac-induced recycling motion of the domain walls, possibly via a supercritical Hopf bifurcation.…”

Green-function approach to transport phenomena in quantum pumps

“…[31][32][33][34] In these problems, the time-dependent part of the Hamiltonian is restricted to a single point, 25,26 a single bond [31][32][33][34] or to the contacts, 23,30 while approximations are introduced to deal with more general situations. 24,[27][28][29] In this work, we present a general treatment based on nonequilibrium Green functions to study transport phenomena in systems described by tight-binding models in contact with particle reservoirs with several time-periodic local potentials. We follow the main lines of Refs.…”

“…In the context of transport problems with time-dependent fields, there are also basic proposals of this type of strategies [23,24] but, in comparison, not so many recent developments. Some examples are studies on ac-driven quantum dots and superlattices [25,26,27,28], the latter restricted to weakly coupled quantum wells, studies on the dynami-cal Franz-Keldysh effect [29], superconducting point contacts with a time-dependent voltage [30], and conducting rings threaded by a time-dependent magnetic flux [31,32,33,34]. In these problems, the time-dependent part of the Hamiltonian is restricted to a single point [25,26], bond [31,32,33,34] or contacts [23,30], while approximations are introduced to deal with more gereral situations [24,27,28,29].…”