arXiv subjects

S. C. Dultz

Publications and source records attributed to S. C. Dultz.

5 recordsLinked to original sources

arXiv2002

Thermodynamic Compressibility of a Two-Dimensional Electron System: Signature of a Droplet State

We have used a field-penetration method to measure thermodynamic compressibility of a moderately interacting two-dimensional electron system ($r_{s}$ $\approx$ 0.5-3) in a three terminal GaAs/AlGaAs device, fabricated with an epitaxial lift-off technique. We found that the density and temperature dependencies of the compressibility are qualitatively different from that observed in earlier studies of the 2D hole system, where interaction energies are considerably stronger. We show that the observed characteristics can be described by the recently developed formalism for compressibility of the droplet state.

cond-mat.str-el↗

arXiv2002

Compressibility of a two-dimensional hole gas in tilted magnetic field

We have measured compressibility of a two-dimensional hole gas in p-GaAs/AlGaAs heterostructure, grown on a (100) surface, in the presence of a tilted magnetic field. It turns out that the parallel component of magnetic field affects neither the spin splitting nor the density of states. We conclude that: (a) g-factor in the parallel magnetic field is nearly zero in this system; and (b) the level of the disorder potential is not sensitive to the parallel component of the magnetic field.

cond-mat.str-el↗

arXiv2001

Universal Quantum Gates for Single Cooper Pair Box Based Quantum Computing

We describe a method for achieving arbitrary 1-qubit gates and controlled-NOT gates within the context of the Single Cooper Pair Box (SCB) approach to quantum computing. Such gates are sufficient to support universal quantum computation. Quantum gate operations are achieved by applying sequences of voltages and magnetic fluxes to single qubits or pairs of qubits. Neither the temporal duration, nor the starting time, of a gate operation is used as a control parameter. As a result, the quantum gates have a constant and known duration, and depend upon standard control parameter sequences regardless of when the gate operation begins. This simplifies the integration of quantum gates into parallel, synchronous, quantum circuits. In addition, we demonstrate the ability to fabricate such gates, and large-scale quantum circuits, using current e-beam lithography technology. These features make the SCB-based scheme a credible contender for practical quantum computer hardware.

quant-ph↗

arXiv1999

Thermodynamic Signature of a Two-Dimensional Metal-Insulator Transition

We present a study of the compressibility, K, of a two-dimensional hole system which exhibits a metal-insulator phase transition at zero magnetic field. It has been observed that dK/dp changes sign at the critical density for the metal-insulator transition. Measurements also indicate that the insulating phase is incompressible for all values of B. Finally, we show how the phase transition evolves as the magnetic field is varied and construct a phase diagram in the density-magnetic field plane for this system.

cond-mat.mes-hall↗

arXiv1998

Absence of Floating Delocalized States in a Two-Dimensional Hole Gas

By tracking the delocalized states of the two-dimensional hole gas in a p-type GaAs/AlGaAs heterostructure as a function of magnetic field, we mapped out a phase diagram in the density-magnetic-field plane. We found that the energy of the delocalized state from the lowest Landau level flattens out as the magnetic field tends toward zero. This finding is different from that for the two-dimensional electron system in an n-type GaAs/AlGaAs heterostructure where delocalized states diverge in energy as B goes to zero indicating the presence of only localized states below the Fermi energy. The possible connection of this finding to the recently observed metal-insulator transition at B = 0 in the two-dimensional hole gas systems is discussed.

cond-mat.mes-hall↗