Magnetic-field dependence of tunnel couplings in carbon nanotube quantum dots.
By means of sequential and cotunneling spectroscopy, we study the tunnel couplings between metallic leads and individual levels in a carbon nanotube quantum dot. The levels are ordered in shells consisting of two doublets with strong- and weak-tunnel couplings, leading to gate-dependent level renormalization. By comparison to a one- and two-shell model, this is shown to be a consequence of disorder-induced valley mixing in the nanotube. Moreover, a parallel magnetic field is shown to reduce this mixing and thus suppress the effects of tunnel renormalization.
NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi, Japan. k_grove@fys.ku.dk
K
K
Grove-Rasmussen
S
S
Grap
J
J
Paaske
K
K
Flensberg
S
S
Andergassen
V
V
Meden
H I
HI
Jørgensen
K
K
Muraki
T
T
Fujisawa