Mesoscopic Fano effect in a quantum dot embedded in an Aharonov-Bohm ring

Abstract

The Fano effect, which occurs through the quantum-mechanical cooperation between resonance and interference, can be observed in electron transport through a hybrid system of a quantum dot and an Aharonov-Bohm ring. While a clear correlation appears between the height of the Coulomb peak and the real asymmetric parameter q for the corresponding Fano line shape, we need to introduce a complex q to describe the variation of the line shape by the magnetic and electrostatic fields. The present analysis demonstrates that the Fano effect with complex asymmetric parameters provides a good probe to detect a quantum-mechanical phase of traversing electrons.

Fano resonance in a quantum wire with a side-coupled quantum dot

“…The characteristics of the two-dimensional electron gas (2DEG) were as follows: mobility = 9 × 10 5 cm 2 /Vs, sheet carrier density = 3.8 × 10 11 cm −2 , and electron mean free path l e = 8 µm. This device is similar to what we had previously studied 16,17 . Two sets of three fingers are Au/Ti metallic gates for controlling the local electrostatic potential.…”

“…3 (a) is obtained at B = 0.80 T. The Fano effect in this system has been observed at several magnetic fields, as was also the case in the Fano effect in the QD-AB-ring system 16,17 . In the present case, the role of the magnetic field can be understood because the QW between the QD and the junction is curved as shown in Fig.…”

“…It has been predicted that the Fano effect appears in a QD embedded in an AB ring as schematically shown in Fig. 1 (a) 15 , and recently, we have reported on its first experimental observation 16,17 .…”

“…The Fano effect is expected to occur in the T-coupled QD in a way different from that in the QD-AB-ring system, because only reflected electrons at the QD are involved for its emergence. In the Fano effect in the QD-AB-ring system reported previously 16,17 , the transmission through the QD played a central role as manifested in the amplitude of the AB oscillation that was in the same order of the Coulomb peak height. Thus, two types of Fano effect can be defined as "reflection mode" and as "transmission mode".…”

Equivalence of the effective Hamiltonian approach and the Siegert boundary condition for resonant states

“…Quantum resonance, in particular, has been a central issue of quantum mechanics from the early days of its development [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. It is ever more important these days because we can closely observe and even manipulate quantum-mechanical systems such as mesoscopic systems, molecules and nuclides [16][17][18][19][20][21]: for example, the resonant conduction in experiments of mesoscopic systems yields a variety of functions of nano-devices; producing unstable nuclides experimentally is nothing but looking for resonant states. It may be said, however, that such experimental studies on quantum resonance far surpass theoretical ones.…”