Damages for Insider Trading in the Open Market: A New Limitation on Recovery Under Rule 10b-5

The Elkind court\u27s adoption of a disgorgement measure of damages for insider trading on undisclosed misrepresented material information in the open market is basically sound. In allowing compensation to the extent practicable, the Second Circuit chose the best solution among the available alternatives. The decision\u27s paramount problems arise in its shifted emphasis to deterrence; the court has neither provided plaintiffs with a sufficient incentive to sue nor created the level of deterrence that some cases might require. Future courts, however, can remedy this situation if they follow Elkind and also award punitive damages in cases in which plaintiffs\u27 losses exceed defendant\u27s profits

Neutron diffraction investigation of the H-T phase diagram above the longitudinal incommensurate phase of BaCo2V2O8

The quasi-one-dimensional antiferromagnetic Ising-like compound BaCo2V2O8 has been shown to be describable by the Tomonaga-Luttinger liquid theory in its gapless phase induced by a magnetic field applied along the Ising axis. Above 3.9 T, this leads to an exotic field-induced low-temperature magnetic order, made of a longitudinal incommensurate spin-density wave, stabilized by weak interchain interactions. By single-crystal neutron diffraction we explore the destabilization of this phase at a higher magnetic field. We evidence a transition at around 8.5 T towards a more conventional magnetic structure with antiferromagnetic components in the plane perpendicular to the magnetic field. The phase diagram boundaries and the nature of this second field-induced phase are discussed with respect to previous results obtained by means of nuclear magnetic resonance and electron spin resonance, and in the framework of the simple model based on the Tomonaga-Luttinger liquid theory, which obviously has to be refined in this complex system.Comment: 7 pages, 5 figure

Field-induced magnetic behavior in quasi-one-dimensional Ising-like antiferromagnet BaCo2V2O8: A single-crystal neutron diffraction study

BaCo2V2O8 is a nice example of a quasi-one-dimensional quantum spin system that can be described in terms of Tomonaga-Luttinger liquid physics. This is explored in the present study where the magnetic field-temperature phase diagram is thoroughly established up to 12 T using single-crystal neutron diffraction. The transition from the N\'eel phase to the incommensurate longitudinal spin density wave (LSDW) phase through a first-order transition, as well as the critical exponents associated with the paramagnetic to ordered phase transitions, and the magnetic order both in the N\'eel and in the LSDW phase are determined, thus providing a stringent test for the theory.Comment: 17 pages with 15 figure

Real time decoherence of Landau and Levitov quasi-particles in quantum Hall edge channels

Quantum Hall edge channels at integer filling factor provide a unique test-bench to understand decoherence and relaxation of single electronic excitations in a ballistic quantum conductor. In this Letter, we obtain a full visualization of the decoherence scenario of energy (Landau) and time (Levitov) resolved single electron excitations at filling factor $\nu=2$. We show that the Landau excitation exhibits a fast relaxation followed by spin-charge separation whereas the Levitov excitation only experiences spin-charge separation. We finally suggest to use Hong-Ou-Mandel type experiments to probe specific signatures of these different scenarios.Comment: 14 pages, 8 figure

Longitudinal and Transverse Zeeman Ladders in the Ising-Like Chain Antiferromagnet BaCo2V2O8

We explore the spin dynamics emerging from the N\'eel phase of the chain compound antiferromagnet BaCo2V2O8. Our inelastic neutron scattering study reveals unconventional discrete spin excitations, so called Zeeman ladders, understood in terms of spinon confinement, due to the interchain attractive linear potential. These excitations consist in two interlaced series of modes, respectively with transverse and longitudinal polarization. The latter have no classical counterpart and are related to the zero-point fluctuations that weaken the ordered moment in weakly coupled quantum chains. Our analysis reveals that BaCo2V2O8, with moderate Ising anisotropy and sizable interchain interactions, remarkably fulfills the conditions necessary for the observation of these longitudinal excitations.Comment: 5 pages, 4 figures, 2 additional pages of supplemental material with 2 figures; Journal ref. added; 1 page erratum added at the end with 1 figur

Raman scattering through surfaces having biaxial symmetry

Magnetic Raman scattering in two-leg spin ladder materials and the relationship between the anisotropic exchange integrals are analyzed by P. J. Freitas and R. R. P. Singh in Phys. Rev. B, {\bf 62}, 14113 (2000). The angular dependence of the two-magnon scattering is shown to provide information for the magnetic anisotropy in the Sr_14Cu_24O_41 and La_6Ca_8Cu_24O_41 compounds. We point out that the experimental results of polarized Raman measurements at arbitrary angles with respect to the crystal axes have to be corrected for the light ellipticity induced inside the optically anisotropic crystals. We refer quantitatively to the case of Sr_14Cu_24O_41 and discuss potential implications for spectroscopic studies in other materials with strong anisotropy.Comment: To be published as a Comment in Phys. Rev.

Half-ordered state in the anisotropic Haldane-gap antiferromagnet NDMAP

Neutron diffraction experiments performed on the Haldane gap material NDMAP in high magnetic fields applied at an angle to the principal anisotropy axes reveal two consecutive field-induced phase transitions. The low-field phase is the gapped Haldane state, while at high fields the system exhibits 3-dimensional long-range Neel order. In a peculiar phase found at intermediate fields only half of all the spin chains participate in the long-range ordering, while the other half remains disordered and gapped.Comment: 4 pages, 2 figures, submitted to Phys. Rev.

Cooperative ordering of gapped and gapless spin networks in Cu2_2Fe2_2Ge4_4O13_{13}

The unusual magnetic properties of a novel low-dimensional quantum ferrimagnet Cu$_2$Fe$_2$Ge$_4$O$_{13}$ are studied using bulk methods, neutron diffraction and inelastic neutron scattering. It is shown that this material can be described in terms of two low-dimensional quantum spin subsystems, one gapped and the other gapless, characterized by two distinct energy scales. Long-range magnetic ordering observed at low temperatures is a cooperative phenomenon caused by weak coupling of these two spin networks.Comment: 4 pages, 4 figure