I will discuss some recent experimental examples from my lab studying quantum coherent transport and interferometry in electrons as well as cold atoms. For example, phase coherent electron transport and interference around a cylinder realized in a nanowire of topological insulator gives rise to a novel “pi phase shifted” Aharonov-Bohm oscillation in the electrical conductance versus magnetic field. The phase of this electron interferometer can be further switched between 0 and pi by tuning the chemical potential of the electrons using a gate voltage, and the electronic conductance oscillates whenever the circumference of the cylinder encloses an integer number of the Fermi wavelengths. These observations reveal the unique signatures of the so called “spin-helical” Dirac electrons on the surface of a topological insulator. In another example, we realize an atomic interferometer in the momentum space in an Bose-Einstein condensate (BEC) subjected to a Raman optical coupling with time-periodic modulation. This creates a so called “synthetic” spin-orbit-coupling and “dressed” band structures (modified energy-momentum dispersions) for the atoms with two avoided crossings in the band structures acting as two beam splitters in the momentum space. Transporting (using for example gravity) the atomic BEC across this “synthetic” bandstructure with two beam splitters gives rise to the Landau-Zener-Stuckelberg interference, manifesting as an oscillation in the spin polarization versus experimental parameters that varies the phase difference between the two pathways traversed by the atoms in the momentum space.
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121 Burton Morgan, Purdue University, West Lafayette, IN