6,634 research outputs found
Two-dimensional electron system in high magnetic fields: Wigner crystal vs. composite-fermion liquid
The two dimensional system of electrons in a high magnetic field offers an
opportunity to investigate a phase transition from a quantum liquid into a
Wigner solid. Recent experiments have revealed an incipient composite fermion
liquid in a parameter range where theory and many experiments had previously
suggested the Wigner crystal phase, thus calling into question our current
understanding. This Letter shows how very small quantitative corrections (< 1%)
in the energy due to the weak interaction between composite fermions can cause
a fundamental change in the nature of the ground state, thus providing insight
into the puzzling experimental results.Comment: 4 pages, 2 figure
Reconstructing the electron in a fractionalized quantum fluid
The low energy physics of the fractional Hall liquid is described in terms
quasiparticles that are qualitatively distinct from electrons. We show,
however, that a long-lived electron-like quasiparticle also exists in the
excitation spectrum: the state obtained by the application of an electron
creation operator to a fractional quantum Hall ground state has a non-zero
overlap with a complex, high energy bound state containing an odd number of
composite-fermion quasiparticles. The electron annihilation operator similarly
couples to a bound complex of composite-fermion holes. We predict that these
bound states can be observed through a conductance resonance in experiments
involving a tunneling of an external electron into the fractional quantum Hall
liquid. A comment is made on the origin of the breakdown of the Fermi liquid
paradigm in the fractional hall liquid.Comment: 5 pages, 2 figure
Flavor altering excitations of composite fermions
Past theoretical studies have considered excitations of a given flavor of
composite fermions across composite-fermion quasi-Landau levels. We show that
in general there exists a ladder of flavor changing excitations in which
composite fermions shed none, some, or all of their vortices. The lowest energy
excitations are obtained when the composite fermions do not change their
flavor, whereas in the highest energy excitations they are stripped of all of
their vortices, emerging as electrons in the final state. The results are
relevant to the intriguing experimental discovery of Hirjibehedin {\em et al.}
(cond-mat/0306152) of coexisting excitation modes of composite fermions of
different flavor in the filling factor range .Comment: 5 pages, 4 figure
Quantum Hall Phase Diagram of Second Landau-level Half-filled Bilayers: Abelian versus Non-Abelian States
The quantum Hall phase diagram of the half-filled bilayer system in the
second Landau level is studied as a function of tunneling and layer separation
using exact diagonalization. We make the striking prediction that bilayer
structures would manifest two distinct branches of incompressible fractional
quantum Hall effect (FQHE) corresponding to the Abelian 331 state (at moderate
to low tunneling and large layer separation) and the non-Abelian Pfaffian state
(at large tunneling and small layer separation). The observation of these two
FQHE branches and the quantum phase transition between them will be compelling
evidence supporting the existence of the non-Abelian Pfaffian state in the
second Landau level.Comment: 4 pages, 3 figure
Trends and uptake of new formulations of controlled-release oxycodone in Canada
Purpose: This study investigated the impact of changing availability of tamperādeterrent and nonātamperādeterrent oxycodone on prescribing patterns of controlledārelease oxycodone across Canada. Methods: We conducted a populationābased, serial crossāsectional study of controlledārelease oxycodone dispensing from community pharmacies across Canada between October 2007 and April 2016. We calculated rates of dispensing (tablets per 100 population) and reported the relative market share of generic nonātamperādeterrent controlledārelease oxycodone. All analyses were reported nationally and stratified by province. Results: After the introduction of a tamperādeterrent formulation, the national rate of controlledārelease oxycodone dispensing fell by 44.6% (from 26.4 to 14.6 tablets per 100 population from February 2012 to April 2016). Between December 2012 and July 2013, there was moderate uptake of generic nonātamperādeterrent controlledārelease oxycodone (968 452 tablets; 16.0% in July 2013), which appeared to have little impact on the overall rate of controlledārelease oxycodone dispensing in Canada. However, the uptake of generic nonātamperādeterrent oxycodone varied considerably by province. By April 2016, 55.0% of all controlledārelease oxycodone tablets dispensed in Quebec were for the generic formulation. [ā¦
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