2,771 research outputs found
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
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 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
Self-consistent Coulomb picture of an electron-electron bilayer system
In this work we implement the self-consistent Thomas-Fermi approach and a
local conductivity model to an electron-electron bilayer system. The presence
of an incompressible strip, originating from screening calculations at the top
(or bottom) layer is considered as a source of an external potential
fluctuation to the bottom (or top) layer. This essentially yields modifications
to both screening properties and the magneto-transport quantities. The effect
of the temperature, inter-layer distance and density mismatch on the density
and the potential fluctuations are investigated. It is observed that the
existence of the incompressible strips plays an important role simply due to
their poor screening properties on both screening and the magneto-resistance
(MR) properties. Here we also report and interpret the observed MR Hysteresis
within our model.Comment: 12 pages, 12 figures, submitted to PR
- …