Tunneling enhancement through a barrier surrounded by a mesoscopic cavity

Abstract

We examine the conductance behavior of a cavity containing a relatively opaque transverse barrier. We show that the transmission of this structure is strongly dependent on the longitudinal position of the barrier and, in particular, has a maximum value when the barrier is located exactly in the middle of the cavity. In this specific condition the overall conductance is much greater than that associated with the barrier alone. Finally we propose a physical interpretation for the obtained numerical results

Symmetry-dependent transport behavior of graphene double dots

“…3, we report the conductance, as a function of the injection energy, of the tunnel barrier alone (grey solid curve a), of the cavity alone (grey dotted curve b), of the cavity with the barrier exactly in the middle (black solid curve c), and of the cavity with the barrier shifted from the center by 10 nm (black dotted curve d). Comparing these results with those obtained in the case of semiconductor heterostructures, 16,17,19 we see that here the presence of two constrictions symmetrically located around the barrier does not enhance its transmission, but rather decreases it by a significant amount. However, if the barrier is shifted away from the center of the cavity (i.e., the symmetry is broken), the transmission exhibits a clear decrease, even though this effect is now apparent only for higher energies and is less dramatic than in semiconductor heterostructures.…”

“…A significant research activity has focused on ballistic or quasi-ballistic devices fabricated at the micro-and nano-scale by confining the 2DEG present in such heterostructures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . We have recently discovered 16,17 an interesting conductance enhancement effect that occurs in symmetric mesoscopic cavities with a barrier in the middle. A mesoscopic cavity is a region of 2-dimensional electron gas connected to input and exit leads (parallel to the transport direction) by constrictions that are usually much narrower than the cavity.…”

Equivalent resistance and noise of cascaded mesoscopic cavities

“…Therefore, if the cavities are exactly identical, the propagating longitudinal modes (propagating because there actually are openings) of each cavity have nodes also in correspondence with all the other constrictions. Thus, the presence of the other constrictions does not have a large effect on conductance and noise (a similar effect could be also the explanation for the strong dependence of the conductance of a cavity containing a transverse potential barrier on the longitudinal position of the barrier, which has been observed recently [15]). The concurrent presence of a beaming effect, i.e.…”

Optimization of the Sensitivity of a Double-Dot Magnetic Detector

“…We have previously reported a somewhat counterintuitive effect [1][2][3] that consists of the conductance enhancement that can be observed, as a result of constructive path interference, when two constrictions are added around a potential barrier, within an electron waveguide. The two symmetric constrictions, instead of further lowering the conductance, lead to its increase, by up to about an order of magnitude [2].…”