Mark W. Keller

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We derive equations for the phase noise spectrum of a spin torque oscillator in the macrospin approximation for the highly symmetric geometry where the equilibrium magnetization, applied field, anisotropy, and spin accumulation are all collinear. This particular problem is one that can be solved by analytical methods, but nevertheless illustrates several(More)
We have fabricated ballistic cavities from a two-dimensional GaAs electron gas in which the Fermi energy can be varied independent of cavity shape. For each cavity, we have measured the magnetoconductance G(B) of many individual members of an ensemble, with each member labeled by its Fermi energy. We find that G(B) of a single ensemble member does not(More)
Nested PCR remains a labor-intensive and error-prone biomolecular analysis. Laboratory workflow automation by precise control of minute liquid volumes in centrifugal microfluidic Lab-on-a-Chip systems holds great potential for such applications. However, the majority of these systems require costly custom-made processing devices. Our idea is to augment a(More)
Attosecond spectroscopic techniques have made it possible to measure differences in transport times for photoelectrons from localized core levels and delocalized valence bands in solids. We report the application of attosecond pulse trains to directly and unambiguously measure the difference in lifetimes between photoelectrons born into free electron-like(More)
A single-electron transistor (SET) is used to detect tunneling of single electrons into individual InGaAs self-assembled quantum dots (QDs). By using an SET with a small island area and growing QDs with a low density we are able to distinguish and measure three QDs. The bias voltage at which resonant tunneling into the dots occurs can be shifted using a(More)
—We have developed a seven-junction electron pump for use in a new standard of capacitance based on measuring the voltage produced when a known charge is placed on a capacitor. This new pump, with an error per pumped electron of 152 2 210 09 , is about 30 times more accurate than a five-junction pump made previously at NIST. By careful design of the pump(More)
Abal~ct We have studied electron heating in a 2DEG in GaAs/AIGaAs heterojunctions below 0.5 IC The electron temperature was raised above the lattice temperature using Joule heat/n& Weak localiT~tion and the temperature-dependent sample resistance were used as thermometers for the electrons. The electron-phonon energy relaxation rate was found to be(More)