Extremely Correlated Fermi Liquid Description of Normal State ARPES in Cuprates

The normal state single particle spectral function of the high temperature superconducting cuprates, measured by the angle resolved photoelectron spectroscopy (ARPES), has been considered both anomalous and crucial to understand. Here we show that an unprecedentedly detailed description of the data is provided by a spectral function arising from the Extremely Correlated Fermi Liquid state of the t-J model proposed recently by Shastry. The description encompasses both laser and conventional synchrotron ARPES data on optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, and also conventional synchrotron ARPES data on the La$_{1.85}$Sr$_{0.15}$CuO$_4$ materials. {\em It fits all data sets with the same physical parameter values}, satisfies the particle sum rule and successfully addresses two widely discussed "kink" anomalies in the dispersion.Comment: Published version, 5 figs; published 29 July (2011

Genetic susceptibility to advanced retinopathy of prematurity (ROP)

Retinopathy of prematurity (ROP) is a vascular vitreoretinopathy that affects infants with short gestational age and low birth-weight. The condition is a multifactorial disease and is clinically similar to familial exudative vitreoretinopathy (FEVR), which is a bilateral hereditary eye disorder affecting full-term infants. Both of them are characterized by the abnormal vessel growth in the vitreous that can lead to vitreoretinal traction, retinal detachment and other complications resulting in blindness. Despite the recent advances in diagnosis and treatment, ROP remains a major cause of childhood blindness in developed countries. The etiology of pathogenesis of advanced ROP is currently unknown. In the past, many causative factors such as length of time exposed to supplemental oxygen, excessive ambient light exposure and hypoxia have been suggested but evidence for these as independent risk factors in recent years is not compelling. It is not clear why ROP in a subset of infants with low birth-weight progresses to a severe stage (retinal detachment) despite timely intervention whereas in other infants with similar clinical characteristics ROP regresses spontaneously. Recent research with candidate gene approach, higher concordance rate in monozygotic twins and other clinical and experimental animal studies, suggest a strong genetic predisposition to ROP besides environmental factors such as prematurity. Three genes, which are involved in the Wnt signaling pathway, are mutated in both FEVR and in a small percentage of ROP disorder. However, none of the genetic factors identified thus far in ROP, account for a substantial number of patient population. Future studies involving genomics, bioinformatics and proteomics may provide a better understanding of the pathophysiology and management of ROP

Universal features of Thermopower in High Tc systems and Quantum Criticality

In high Tc superconductors a wide ranging connection between the doping dependence of the transition temperature Tc and the room temperature thermopower Q has been observed. A "universal correlation" between these two quantities exists with the thermopower vanishing at optimum doping as noted by OCTHH (Obertelli, Cooper, Tallon, Honma and Hor). In this work we provide an interpretation of this OCTHH universality in terms of a possible underlying quantum critical point (QCP) at Tc. Central to our viewpoint is the recently noted Kelvin formula relating the thermopower to the density derivative of the entropy. Perspective on this formula is gained through a model calculation of the various Kubo formulas in an exactly solved 1-dimensional model with various limiting procedures of wave vector and frequency.Comment: 12 pages, 8 figure

Resonant Two-Magnon Raman Scattering and Photoexcited States in Two-Dimensional Mott Insulators

We investigate the resonant two-magnon Raman scattering in two-dimensional (2D) Mott insulators by using a half-filled 2D Hubbard model in the strong coupling limit. By performing numerical diagonalization calculations for small clusters, we find that the Raman intensity is enhanced when the incoming photon energy is not near the optical absorption edge but well above it, being consistent with experimental data. The absence of resonance near the gap edge is associated with the presence of background spins, while photoexcited states for resonance are found to be characterized by the charge degree of freedom. The resonance mechanism is different from those proposed previously.Comment: REVTeX4, 4 pages, 3 figures, to be published in Phys. Rev. Let

A class of Heisenberg models with the orthogonal dimer ground states

Extensions of the Shastry-Sutherland model are possible in various ways. In particular, it is possible to construct a natural model in three dimensions which has the exact dimer ground state. Recently found spin gap system SrCu_2(BO_3)_2 has this structure. The exchange constants between the layers is expected to be smaller than the intra-layer couplings. However, the exactness of the dimer state for the three dimensional structure is important to understand why magnetic properties of SrCu_2(BO_3)_2 are described well by the two dimensional model.Comment: 3 pages, 5 figures, to appear in Journal of Physics: Condensed Matte

Microscopic mechanism for the 1/8 magnetization plateau in SrCu_2(BO_3)_2

The frustrated quantum magnet SrCu_2(BO_3)_2 shows a remarkably rich phase diagram in an external magnetic field including a sequence of magnetization plateaux. The by far experimentally most studied and most prominent magnetization plateau is the 1/8 plateau. Theoretically, one expects that this material is well described by the Shastry-Sutherland model. But recent microscopic calculations indicate that the 1/8 plateau is energetically not favored. Here we report on a very simple microscopic mechanism which naturally leads to a 1/8 plateau for realistic values of the magnetic exchange constants. We show that the 1/8 plateau with a diamond unit cell benefits most compared to other plateau structures from quantum fluctuations which to a large part are induced by Dzyaloshinskii-Moriya interactions. Physically, such couplings result in kinetic terms in an effective hardcore boson description leading to a renormalization of the energy of the different plateaux structures which we treat in this work on the mean-field level. The stability of the resulting plateaux are discussed. Furthermore, our results indicate a series of stripe structures above 1/8 and a stable magnetization plateau at 1/6. Most qualitative aspects of our microscopic theory agree well with a recently formulated phenomenological theory for the experimental data of SrCu_2(BO_3)_2. Interestingly, our calculations point to a rather large ratio of the magnetic couplings in the Shastry-Sutherland model such that non-perturbative effects become essential for the understanding of the frustrated quantum magnet SrCu_2(BO_3)_2.Comment: 24 pages, 24 figure

Consumer Attitude and their Purchase Intention: A Review of Literature

The objective of the paper is to bring spotlight on literature related to consumer attitude and purchase intention. The Paper attempts to identify and segregate factors which are vital and critical antecedents to formation of consumer attitude consequently “Intention to purchase”. For this purpose over 200 Journal articles were scrutinized on pre-set parameters, while 25 of them that are relevant research papers presented here. The factors considered include social media, traditional media, Word of mouth, message process involvement and trust. The findings of the study include a gamut of research objectives and aims, host of pertinent scales, commonly adopted methodologies, variety of variables and opportunity for conducting impactful research