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Nakamura, James

Publications and source records attributed to Nakamura, James.

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Optimization of submicron Ni/Au/Ge contacts to an AlGaAs/GaAs two-dimensional electron gas

We report on fabrication and performance of sub-micrometer Ni/Au/Ge contacts to a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. Utilizing scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and low temperature electrical measurements, we investigate the relationship between contact performance and the mechanical and chemical properties of the annealed metal stack. Contact geometry and crystallographic orientation significantly impact performance. Our results indicate that the spatial distribution of germanium in the annealed contact plays a central role in the creation of high transmission contacts. We characterize the transmission of our contacts at high magnetic fields in the quantum Hall regime. Our work establishes that contacts with an area of 0.5 μm2 and resistance less than 400 Ω can be fabricated with high yield.

Physics↗
DOE OSTI2020

Direct observation of anyonic braiding statistics

Anyons are quasiparticles that, unlike fermions and bosons, show fractional statistics when two of them are exchanged. Here, we report experimental observation of anyonic braiding statisticsfor the ν 1/3 fractional quantum Hall state using a device that is equivalent to a Fabry-Perot interferometer. Strong Aharonov-Bohm interference of the edge mode is punctuated by discrete phase slips that indicate an anyonic phase of $\theta$ anyon = 2π/3. Here, our results are consistent with a recent theory for an interferometer operated in a regime in which device charging energy is small compared to the energy of formation of charged quasiparticles, indicating that we have observed anyonic braiding.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗