Figure 1
(Color online) Transmission amplitude per spin,
, through a spinful two-level quantum dot for various temperatures and constant couplings. Regimes (i), (ii), indicated in panel (a) only, refer to Kondo valleys or Coulomb blockade valleys, respectively (see text). The levels involved are indicated by their level number 1,2. Level 2 is coupled more strongly to the leads than level 1, resulting in different bare Kondo temperatures, e.g.,
. We use
(a,c) and
(b,d), thus
. The minimum value of the
(in the center of the Kondo valleys) are indicated in the legends. In accordance with Ref.
24, we find shoulders in the phase [see, e.g., the fat arrow and the dashed curve
in (c) for level 1] and an enhanced sensitivity of the phase to Kondo correlations compared to the magnitude, see e.g., the dashed-dotted
curves in (d) for level 1 or the dashed curve
for level 2 in (a). There, the typical
-Kondo plateau in the phase is present, whereas the Kondo plateau in amplitude is not fully developed yet. At certain points in gate voltage, say
(as indicated by thin arrows), we find stationary points where the curves for
for all temperatures intersect. The position of
is shifted by the presence of a neighboring level, being repelled by or shifted towards the latter for
or
, compare (a,c) or (b,d), respectively. Depending on the mesoscopic parameter
, the phase either exhibits a sharp drop of
, accompanied by a zero in the amplitude
[
, see (a,b)], or increases monotonically [
, see (c,d)] in the Coulomb blockade valleys.
Reuse & Permissions