Transport through nanostructures with asymmetric coupling to the leads

Abstract

Using an approach to open quantum systems based on the effective non-Hermitian Hamiltonian, we fully describe transport properties for a paradigmatic model of a coherent quantum transmitter: a finite sequence of square potential barriers. We consider the general case of asymmetric external barriers and variable coupling strength to the environment. We demonstrate that transport properties are very sensitive to the degree of opening of the system and determine the parameters for maximum transmission at any given degree of asymmetry. Analyzing the complex eigenvalues of the non-Hermitian Hamiltonian, we show a double transition to a super-radiant regime where the transport properties and the structure of resonances undergo a strong change. We extend our analysis to the presence of disorder and to higher dimensions.

Towards high-temperature coherence-enhanced transport in heterostructures of a few atomic layers

“…We start from an idealized description of the heterostructure where the interlayer transport of a single excitation is modeled by a one dimensional N -site chain connected to one collector and one source. Within this simple approach we obtain analytic expressions to estimate the parameters range compatible with quantum-transport efficiency enhancement, and we are able to connect the optimal transport conditions with the superradiant transition [15][16][17] , which takes place as a function of the ratio between the coupling with the leads γ out and the hopping between the sites of the chain t. When γ out t all the N eigenstates acquire a finite lifetime of the order of N /γ out , thus allowing coherent transport throughout the chain. In the opposite regime γ out t one superradiant edge solution appears, spatially located at the edge (N th ) site, which acquires a broadening much larger than the average one.…”

Resonance width distribution for open quantum systems

“…The deviations from the PTD grow with κ up to the critical strength κ ∼ 1, when the broad "superradiant" state becomes essentially part of the background, while the remaining "trapped" states return to the weak-coupling regime. This physics was repeatedly discussed previously, especially in relation to quantum signal transmission through mesoscopic devices [21,29], but it is outside of our interest here.…”

Quantum thermostatted disordered systems and sensitivity under compression

“…Indeed, since Anderson's paper, the study of electron transport has played a key role in the development of modern solid state physic, see for instance Refs. [6,7,8] and references therein. The systems of interest, here, are nanostructured devices made of an insulating matrix embedding randomly distributed drops of conducting material.…”