515 research outputs found
Transport Properties of Carbon Nanotube C Peapods
We measure the conductance of carbon nanotube peapods from room temperature
down to 250mK. Our devices show both metallic and semiconducting behavior at
room temperature. At the lowest temperatures, we observe single electron
effects. Our results suggest that the encapsulated C molecules do not
introduce substantial backscattering for electrons near the Fermi level. This
is remarkable given that previous tunneling spectroscopy measurements show that
encapsulated C strongly modifies the electronic structure of a nanotube
away from the Fermi level.Comment: 9 pages, 4 figures. This is one of two manuscripts replacing the one
orginally submitted as arXiv:cond-mat/0606258. The other one is
arXiv:0704.3641 [cond-mat
Effect of calcium supplements on risk of myocardial infarction and cardiovascular events : meta-analysis
Peer reviewedPublisher PD
Tunable singlet-triplet splitting in a few-electron Si/SiGe quantum dot
We measure the excited-state spectrum of a Si/SiGe quantum dot as a function
of in-plane magnetic field, and we identify the spin of the lowest three
eigenstates in an effective two-electron regime. The singlet-triplet splitting
is an essential parameter describing spin qubits, and we extract this splitting
from the data. We find it to be tunable by lateral displacement of the dot,
which is realized by changing two gate voltages on opposite sides of the
device. We present calculations showing the data are consistent with a spectrum
in which the first excited state of the dot is a valley-orbit state.Comment: 4 pages with 3 figure
Transport through an impurity tunnel coupled to a Si/SiGe quantum dot
Achieving controllable coupling of dopants in silicon is crucial for
operating donor-based qubit devices, but it is difficult because of the small
size of donor-bound electron wavefunctions. Here we report the characterization
of a quantum dot coupled to a localized electronic state, and we present
evidence of controllable coupling between the quantum dot and the localized
state. A set of measurements of transport through this device enable the
determination of the most likely location of the localized state, consistent
with an electronically active impurity in the quantum well near the edge of the
quantum dot. The experiments we report are consistent with a gate-voltage
controllable tunnel coupling, which is an important building block for hybrid
donor and gate-defined quantum dot devices.Comment: 5 pages, 3 figure
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