3,410 research outputs found
The FIR-absorption of short period quantum wires and the transition from one to two dimensions
We investigate the FIR-absorption of short period parallel quantum wires in a
perpendicular quantizing magnetic field. The external time-dependent electric
field is linearly polarized along the wire modulation. The mutual Coulomb
interaction of the electrons is treated self-consistently in the ground state
and in the absorption calculation within the Hartree approximation. We consider
the effects of a metal gate grating coupler, with the same or with a different
period as the wire modulation, on the absorption. The evolution of the
magnetoplasmon in the nonlocal region where it is split into several Bernstein
modes is discussed in the transition from: narrow to broad wires, and isolated
to overlapping wires. We show that in the case of narrow and not strongly
modulated wires the absorption can be directly correlated with the underlying
electronic bandstructure.Comment: 15 pages, 9 figures, Revtex, to appear in Phys. Rev.
Magnetic-field induced multiferroicity in a quantum critical frustrated spin liquid
Dielectric spectroscopy is used to check for the onset of polar order in the
quasi one-dimensional quantum spin system Sul-Cu2Cl4 when passing from the
spin-liquid state into the ordered spiral phase in an external magnetic field.
We find clear evidence for multiferroicity in this material and treat in detail
its H-T phase diagram close to the quantum-critical regime.Comment: 5 pages, 4 figures. Revised according to suggestions of referee
CF6-6D engine short-term performance deterioration
Studies conducted as part of the NASA-Lewis CF6 jet engine diagnostics program are summarized. An 82-engine sample of DC-10-10 aircraft engine checkout data that were gathered to define the extent and magnitude of CF6-6D short term performance deterioration were analyzed. These data are substantiated by the performance testing and analytical teardown of CF6-6D short term deterioration engine serial number (ESN) 451507
CF6-6D engine performance deterioration
Cruise cockpit recordings and test cell performance data in conjunction with hardware inspection data from airline overhaul shops were analyzed to define the extent and magnitude of performance deterioration of the General Electric CF6-6D model engine. These studies successfully isolated short-term deterioration from the longer term, and defined areas where a significant reduction in aircraft energy requirements for the 1980's can be realized. Unrestored losses which remain after engine refurbishment represent over 70% of the loss at engine shop visit. Sixty-three percent of the unrestored losses are cost-effective to restore which could reduce fuel consumed by CF6-6D engines in 1980 by 10.9 million gallons
Magnetic structure and phase diagram of TmB4
Magnetic structure of single crystalline TmB4 has been studied by
magnetization, magnetoresistivity and specific heat measurements. A complex
phase diagram with different antiferromagnetic (AF) phases was observed below
TN1 = 11.7 K. Besides the plateau at half-saturated magnetization (1/2 MS),
also plateaus at 1/9, 1/8 and 1/7 of MS were observed as function of applied
magnetic field B//c. From additional neutron scattering experiments on TmB4, we
suppose that those plateaus arise from a stripe structure which appears to be
coherent domain boundaries between AF ordered blocks of 7 or 9 lattice
constants. The received results suggest that the frustration among the Tm3+
magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland
lattice lead to strong competition between AF and ferromagnetic (FM) order.
Thus, stripe structures in intermediate field appear to be the best way to
minimize the magnetostatic energy against other magnetic interactions between
the Tm ions combined with very strong Ising anisotropy.Comment: 4 pages, 4 figures, conference contribution - CSMAG 0
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