Showing papers by "Jeremy L. O'Brien published in 1999"

In-Plane Magnetic Field Effect on the Transport Properties in a Quasi-3D Quantum Well Structure

Abstract: The transport properties of a quasi-three-dimensional, 200 layer quantum well structure are investigated at integer filling in the quantum Hall state. We find that the transverse magnetoresistance R xx , the Hall resistance R xy , and the vertical resistance R zz all follow a similar behavior with both temperature and in-plane magnetic field. A general feature of the influence of increasing in-plane field B in is that the Hall conductance quantization first improves, but above a characteristic value B C in , the quantization is systematically removed. We consider the interplay of the chid edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band structure energies. A comparison of the resuIts with existing theories of the chiral edge state transport with in-plane field is also discussed.

Quantum oscillations in quasi-one-dimensional metals with spin-density-wave ground states

Abstract: We consider the magnetoresistance oscillation phenomena in the Bechgaard salts (TMTSF)(2)X, where X = ClO4, PF6, and AsF6 in pulsed magnetic fields to 51 T. Of particular importance is the observation of a new magnetoresistance oscillation for X = ClO4 in its quenched state. In the absence of any Fermi-surface reconstruction due to anion order at low temperatures, all three materials exhibit nonmonotonic temperature dependence of the oscillation amplitude in the spin-density-wave (SDW) state. We discuss a model where, below a characteristic temperature T* within the SDW state, a magnetic breakdown gap opens. [S0163-1829(99)00904-2].

In-plane magnetic-field effect on transport properties of the chiral edge state in a quasi-three-dimensional quantum well structure

Abstract: The transport properties of a quasi-three-dimensional, 200-layer quantum-well structure are investigated at integer filling in the quantum Hall state, concomitant with the chiral edge state condition. We find that the transverse magnetoresistance R{sub xx}, the Hall resistance R{sub xy}, and the vertical resistance R{sub zz} all follow a similar behavior with {ital both} temperature and in-plane magnetic field. A general characteristic of the influence of increasing in-plane field B{sub in} is that the quantization condition first improves, but above a critical value B{sub in}{sup C}, the quantization is systematically removed. We consider the interplay of the chiral edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band-structure energies. A comparison of the results with existing theories of the chiral edge state transport with in-plane field is also discussed. {copyright} {ital 1999} {ital The American Physical Society}

Photonic Crystal Nanocavity Lasers

Abstract: When combined with high index contrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine light into extremely small volumes. We show that these high Q cavities now make it possible to define microcavity lasers which function at room temperature and have mode volumes as small as 2.5 (X/2nsiab)3, or 0.03 urn3 in InGaAsP emitting at 1.55 u,m.