Anomalous Fano Resonance in Double Quantum Dot System Coupled to Superconductor

Abstract

We analyze the influence of a local pairing on the quantum interference in nanoscopic systems. As a model system we choose the double quantum dot coupled to one metallic and one superconducting electrode in the T-shape geometry. The analysis is particularly valuable for systems containing coupled objects with considerably different broadening of energy levels. In such systems, the scattering of itinerant electrons on a discrete (or narrow) energy level gives rise to the Fano-type interference. Systems with induced superconducting order, along well understood Fano resonances, exhibit also another features on the opposite side of the Fermi level. The lineshape of these resonances differs significantly from their reflection on the opposite side of the Fermi level, and their origin was not fully understood. Here, considering the spin-polarized tunneling model, we explain a microscopic mechanism of a formation of these resonances and discuss the nature of their uncommon lineshapes. We show that the anomalous Fano profiles originate solely from the pairing of nonscattered electrons with scattered ones. We investigate also the interplay of each type of resonances with the Kondo physics and discuss the resonant features in differential conductivity.

Dicke and Fano-Andreev reflections in a triple quantum-dot system

“…The shape of the differential conductance may be understood by noticing the quantum interference among the electron trajectories entering and leaving the side-attached quantum dots. These interferences give rise to the so-called Fano-Andreev antiresonances [5][6][7] . On the other hand, the states of two side-attached quantum dots interfere with each other, giving rise to a Dicke-like effect.…”

“…Electron transport through multiple quantum dots systems exhibits exciting interference effects such as Fano [1][2][3][4][5][6][7] and Aharonov-Bohm [8][9][10][11][12] . The interference phenomenon, which resembles the well-known Dicke resonance in atomic physics, appears to be of particular importance 13 .…”

Pseudospin resonances reveal synthetic spin-orbit interaction

“…The ratio has two extrema which stem from minima of the corresponding exchange field components B ↓,⊥ and B ↓, . Despite its superficial resemblance to a Fano resonance, the origin of this peak-dip current resonance cannot be ascribed to the interference processes typical of Fano resonance, also seen in QD setups [40][41][42][43][44].…”

Transport properties of proximitized double quantum dots

“…For the case of one quantum dot attached to one superconducting (SC) and one normal metallic (N) contact (N-QD-SC system), the propagation of a Cooper pair into SC lead and a hole reflection into a metallic lead (Andreev reflection process) occurs in the system [33,34]. The connection of second QD into the N-QD-SC system causes the competition between the Andreev and Fano effect [4,8,15,26,28]. Other options of DQD with SC and N leads connection are also considered, e.g.…”