In semiconductor quantum dots, the Kondo temperature has been observed to depend exponentially on the gate voltage. This dependence arises because in these structures the gate capacitively shifts the ...energy of the singly occupied Kondo-active level relative to the chemical potential of the conduction electrons in the source and drain. In single-molecule transistors incorporating transition metal complexes, we find that the expected gate dependence in the Kondo regime is not observed. While the data show that the gate does shift electronic levels, the Kondo temperature found from both the differential conductance temperature and bias voltage dependence is approximately independent of gate voltage. We discuss possible explanations for this surprising observation, including the possible effect of molecular vibrational modes.
A series of transition metal coordination complexes designed to assemble on gold surfaces was synthesized, their electronic structure and transitions analyzed, and their magnetic properties studied. ...By taking advantage of recently developed thiocyanate assembly protocols, these molecules were then assembled onto a gold surface, without the need for an inert atmosphere, to give a loosely packed monolayer. The assembled molecules exhibit properties similar to that of the bulk molecules, indicating little change in molecular structure outside of chemisorption.
We report the discovery of the optical counterpart to GRB 980326. Its rapid optical decay can be characterized by a power law with exponent Ϫ and a constant underlying source at. Its optical 2.10 ע ...0.13 R ϭ 25.5 ע 0.5 c colors 2.1 days after the burst imply a spectral slope of Ϫ. The gray spectrum as observed with 0.66 ע 0.70 BATSE shows that it is among the 4% softest bursts ever recorded. We argue that the rapid optical decay may be a reason for the nondetection of some low-energy afterglows of GRBs.
We present preliminary measurements of resistively detected nuclear magnetic resonance (NMR) in GaAs-AlGaAs quantum point contacts (QPC). Nuclear spins in the host crystal are polarized through the ...hyperfine interaction with carriers near the QPC; this polarization can be detected via the four-terminal resistance and manipulated with a radio-frequency magnetic field.
We have observed the Autler-Townes doublet in a superconducting Al/AlOx/Al transmon qubit that acts as an artificial atom embedded in a three-dimensional Cu microwave cavity at a temperature of 22 ...mK. Using pulsed microwave spectroscopy, the three lowest transmon levels are isolated, eliminating unwanted effects of higher qubit modes and cavity modes. The long coherence time (~40 us) of the transmon enables us to observe a clear Autler-Townes splitting at drive amplitudes much smaller than the transmon level anharmonicity (177 MHz). Three-level density matrix simulations with no free parameters provide excellent fits to the data. At maximum separation, the fidelity of a dark state achieved in this experiment is estimated to be 99.6-99.9%.
Radio frequency reflectometry is demonstrated in a sub-micron undoped AlGaAs/GaAs device. Undoped single electron transistors (SETs) are attractive candidates to study single electron phenomena due ...to their charge stability and robust electronic properties after thermal cycling. However these devices require a large top-gate which is unsuitable for the fast and sensitive radio frequency reflectometry technique. Here we demonstrate rf reflectometry is possible in an undoped SET.
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