Noncollinear magnetic phases and edge states in graphene quantum Hall bars

Application of a perpendicular magnetic field to charge neutral graphene is expected to result in a variety of broken symmetry phases, including antiferromagnetic, canted, and ferromagnetic. All these phases open a gap in bulk but have very different edge states and noncollinear spin order, recently confirmed experimentally. Here we provide an integrated description of both edge and bulk for the various magnetic phases of graphene Hall bars making use of a noncollinear mean field Hubbard model. Our calculations show that, at the edges, the three types of magnetic order are either enhanced (zigzag) or suppressed (armchair). Interestingly, we find that preformed local moments in zigzag edges interact with the quantum spin Hall like edge states of the ferromagnetic phase and can induce backscattering.

Quantum theory of spin waves in finite chiral spin chains

We calculate the effect of spin waves on the properties of finite-size spin chains with a chiral spin ground state observed on biatomic Fe chains deposited on iridium(001). The system is described with a Heisenberg model supplemented with a Dzyaloshinskii-Moriya coupling and a uniaxial single ion anisotropy that presents a chiral spin ground state. Spin waves are studied using the Holstein-Primakoff boson representation of spin operators. Both the renormalized ground state and the elementary excitations are found by means of Bogoliubov transformation, as a function of the two variables that can be controlled experimentally, the applied magnetic field and the chain length. Three main results are found. First, because of the noncollinear nature of the classical ground state, there is a significant zero-point reduction of the ground-state magnetization of the spin spiral. Second, there is a critical external field from which the ground state changes from chiral spin ground state to collinear ferromagnetic order. The character of the two lowest-energy spin waves changes from edge modes to confined bulk modes over this critical field. Third, in the spin-spiral state, the spin-wave spectrum exhibits oscillatory behavior as function of the chain length with the same period of the spin helix.

Identifying student and teacher difficulties in interpreting atomic spectra using a quantum model of emission and absorption of radiation

Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two questionnaires, one for teachers and the other for students. By analyzing the responses, we conclude that (i) teachers lack a quantum model for the emission and absorption of electromagnetic radiation capable of explaining the spectra, (ii) teachers and students share the same difficulties, and (iii) these difficulties concern the model of the atom, the model of radiation, and the model of the interaction between them.

Additional traffic assignment options for the TASSIM model. Phase I. Final report.

Transportation Department, Washington, D.C.

Integrated traffic simulation model - phase I. Volume 4: revisions to the UTCS-1 traffic simulation model to enhance operational efficiency. Final report.

Federal Highway Administration, Washington, D.C.

Integrated traffic simulation model, phase, I. Volume 1: executive summary. Final report.

Federal Highway Administration, Washington, D.C.

Integrated traffic simulation model - phase I. Volume 2: design of the TRAF system (TOS). Final report.

Federal Highway Administration, Washington, D.C.

Los Angeles and Long Beach Harbors model study : resonant response of the harbors for Phase 1 of the Los Angeles deep-draft dry bulk export terminal /

"January 1984."

Evaluation of flared outlet transitions : hydraulic model investigation /

"June 1972."

Study of the performance of aids to navigation systems : phase 1, closed loop model of the process of navigation /

Final report; March 1978.

A manual of model police traffic services: policies, procedures, rules. Phase III - model police traffic services rules.

National Highway Traffic Safety Administration, Washington, D.C.

The model T Ford car, its construction, operation and repair; a complete practical treatise explaining the operating principles of all parts of the Ford automobile, with complete instructions for driving and maintenance; includes the most thorough and easily understood illustrated instructions on Ford repairing ever published; based on five years' experience of a Ford operator--invaluable to all Ford owners, dealers, salesmen, drivers and repair men--every phase of the subject treated in a non-technical yet comprehensive manner,

Mode of access: Internet.

The Illinois economic model : phase I /

"December, 1977."

Operator, organizational, direct support, and general support maintenance manual : camera, copying, mobile process, 208-volt, 3 phase, 60 hertz, 24 x 30 inch, Consolidated International model 1969 NSN 3610-00-400-7588 ....

"April 1971."