Biomedical subjects

D Reznik

Publications and source records attributed to D Reznik.

16 recordsLinked to original sources

PubMed2006

Quasiparticlelike peaks, kinks, and electron-phonon coupling at the (pi,0) regions in the CMR oxide La2-2x Sr1+2x Mn2 O7.

Using angle-resolved photoemission, we have observed sharp quasiparticlelike peaks in the prototypical layered manganite La(2-2x)Sr(1+2x)Mn(2)O(7) (x=0.36,0.38). We focus on the (pi,0) regions of k space and study their electronic scattering rates and dispersion kinks, uncovering bilayer-split bands, the critical energy scales, momentum scales, and strengths of the interactions that renormalize the electrons. To identify these bosons, we measured phonon dispersions in the energy range of the kink by inelastic neutron scattering, finding a good match in both energy and momentum to the oxygen bond-stretching phonons.

Journal Article↗

PubMed2006

Electron-phonon coupling reflecting dynamic charge inhomogeneity in copper oxide superconductors.

The attempt to understand copper oxide superconductors is complicated by the presence of multiple strong interactions in these systems. Many believe that antiferromagnetism is important for superconductivity, but there has been renewed interest in the possible role of electron-lattice coupling. The conventional superconductor MgB2 has a very strong electron-lattice coupling, involving a particular vibrational mode (phonon) that was predicted by standard theory and confirmed quantitatively by experiment. Here we present inelastic scattering measurements that show a similarly strong anomaly in the Cu-O bond-stretching phonon in the copper oxide superconductors La(2-x)Sr(x)CuO4 (with x = 0.07, 0.15). Conventional theory does not predict such behaviour. The anomaly is strongest in La(1.875)Ba(0.125)CuO4 and La(1.48)Nd(0.4)Sr(0.12)CuO4, compounds that exhibit spatially modulated charge and magnetic order, often called stripe order; it occurs at a wave vector corresponding to the charge order. These results suggest that this giant electron-phonon anomaly, which is absent in undoped and over-doped non-superconductors, is associated with charge inhomogeneity. It follows that electron-phonon coupling may be important to our understanding of superconductivity, although its contribution is likely to be indirect.

Journal Article↗

PubMed2004

Dispersion of magnetic excitations in optimally doped superconducting YBa2Cu3O6.95.

Detailed neutron scattering measurements of YBa2Cu3O6.95 found that the resonance peak and incommensurate magnetic scattering induced by superconductivity represent the same physical phenomenon: two dispersive branches that converge near 41 meV and the in-plane wave vector q(AF)=(pi/a,pi/a) to form the resonance peak. One branch has a circular symmetry around q(AF) and quadratic downward dispersion from approximately 41 meV to the spin gap of 33+/-1 meV. The other, of lower intensity, disperses from approximately 41 meV to at least 55 meV. Our results exclude a quartet of vertical incommensurate rods in q-omega space expected from spin waves produced by dynamical charge stripes as an origin of the observed incommensurate scattering in optimally doped YBCO.

Journal Article↗

PubMed2004

Partial order in the non-Fermi-liquid phase of MnSi.

Only a few metallic phases have been identified in pure crystalline materials. These include normal, ferromagnetic and antiferromagnetic metals, systems with spin and charge density wave order, and superconductors. Fermi-liquid theory provides a basis for the description of all of these phases. It has been suggested that non-Fermi-liquid phases of metals may exist in some heavy-fermion compounds and oxide materials, but the discovery of a characteristic microscopic signature of such phases presents a major challenge. The transition-metal compound MnSi above a certain pressure (p(c) = 14.6 kbar) provides what may be the cleanest example of an extended non-Fermi-liquid phase in a three-dimensional metal. The bulk properties of MnSi suggest that long-range magnetic order is suppressed at p(c) (refs 7-12). Here we report neutron diffraction measurements of MnSi, revealing that sizeable quasi-static magnetic moments survive far into the non-Fermi-liquid phase. These moments are organized in an unusual pattern with partial long-range order. Our observation supports the existence of novel metallic phases with partial ordering of the conduction electrons (reminiscent of liquid crystals), as proposed for the high-temperature superconductors and heavy-fermion compounds.

Journal Article↗

PubMed2001

Clinical treatment evaluations of a new topical oral medication.

Clinical symptoms of viral infections, such as herpes labialis (cold sores) and oral ulcers (canker sores), are common in adulthood, affecting approximately 19% of adults aged 25 to 44 years. For some patients, lesions last longer, are more painful, and are more difficult to treat, requiring medications that allow the affected area to heal but do little to alleviate pain. Conventionally, pain caused by oral ulcerations has been addressed with either topical analgesics or systemic pain medications. However, a recently introduced over-the-counter topical medication (ORABASE Soothe.N.Seal) has been shown to be an effective pain-relieving adjunct to healing therapies. This article reviews the characteristics of painful oral ulcerations and details the research findings of a clinical trial of the use of this new medication.

Adult↗

PubMed1998