Phase diagram and optical conductivity of La1.8-xEu0.2SrxCuO4

La1.8-xEu0.2SrxCuO4 (LESCO) is the member of the 214 family which exhibits the largest intervals among the structural, charge ordering (CO), magnetic, and superconducting transition temperatures. By using new dc transport measurements and data in the literature we construct the phase diagram of LESCO between x = 0.8 and 0.20. This phase diagram has been further probed in ac, by measuring the optical conductivity {\sigma}1({\omega}) of three single crystals with x = 0.11, 0.125, and 0.16 between 10 and 300 K in order to associate the extra-Drude peaks often observed in the 214 family with a given phase. The far-infrared peak we detect in underdoped LESCO is the hardest among them, survives up to room temperature and is associated with charge localization rather than with ordering. At the CO transition for the commensurate doping x = 0.125 instead the extra-Drude peak hardens and a pseudogap opens in {\sigma}1({\omega}), approximately as wide as the maximum superconducting gap of LSCO.Comment: 6 pages, 6 figure

Angular Dependent Spectral-Weight Transfer and Evidence for Symmetry Broken In-Plane Charge Response in Ca1.9_{1.9}Na0.1_{0.1}CuO2_2Cl2_2

We report about the energy and momentum dependent charge response in Ca$_{1.9}$Na$_{0.1}$CuO$_2$Cl$_2$ employing electron energy-loss spectroscopy. Along the diagonal of the Brillouin zone (BZ) we find a plasmon peak---indicating the presence of metallic states in this momentum region---which emerges as a consequence of substantial spectral-weight transfer from excitations across the charge-transfer (CT) gap and is the two-particle manifestation of the small Fermi pocket or arc observed with photoemission in this part of the BZ. In contrast, the spectrum along the [100]-direction is almost entirely dominated by CT excitations, reminiscent of the insulating parent compound. We argue that the observed polarization dependent shape of the spectrum is suggestive of a breaking of the underlying tetragonal lattice symmetry, possibly due to fluctuating nematic order in the charge channel. In addition we find the plasmon bandwidth to be suppressed compared to optimally doped cuprates

Superconductivity Induced by Bond Breaking in the Triangular Lattice of IrTe2

IrTe2, a layered compound with a triangular iridium lattice, exhibits a structural phase transition at approximately 250 K. This transition is characterized by the formation of Ir-Ir bonds along the b-axis. We found that the breaking of Ir-Ir bonds that occurs in Ir1-xPtxTe2 results in the appearance of a structural critical point in the T = 0 limit at xc = 0.035. Although both IrTe2 and PtTe2 are paramagnetic metals, superconductivity at Tc = 3.1 K is induced by the bond breaking in a narrow range of x > xc in Ir1-xPtxTe2. This result indicates that structural fluctuations can be involved in the emergence of superconductivity.Comment: 10 pages, 4 figure

Orbital Degeneracy and Peierls Instability in Triangular Lattice Superconductor Ir1−x_{1-x}Ptx_xTe2_2

We have studied electronic structure of triangular lattice Ir$_{1-x}$Pt$_x$Te$_2$ superconductor using photoemission spectroscopy and model calculations. Ir $4f$ core-level photoemission spectra show that Ir $5d$ $t_{2g}$ charge modulation established in the low temperature phase of IrTe$_2$ is suppressed by Pt doping. This observation indicates that the suppression of charge modulation is related to the emergence of superconductivity. Valence-band photoemission spectra of IrTe$_2$ suggest that the Ir $5d$ charge modulation is accompanied by Ir $5d$ orbital reconstruction. Based on the photoemission results and model calculations, we argue that the orbitally-induced Peierls effect governs the charge and orbital instability in the Ir$_{1-x}$Pt$_x$Te$_2$.Comment: 5 pages,4 figure

Te 5p orbitals bring three-dimensional electronic structure to two-dimensional Ir0.95Pt0.05Te2

We have studied the nature of the three-dimensional multi-band electronic structure in the twodimensional triangular lattice Ir1-xPtxTe2 (x=0.05) superconductor using angle-resolved photoemission spectroscopy (ARPES), x-ray photoemission spectroscopy (XPS) and band structure calculation. ARPES results clearly show a cylindrical (almost two-dimensional) Fermi surface around the zone center. Near the zone boundary, the cylindrical Fermi surface is truncated into several pieces in a complicated manner with strong three-dimensionality. The XPS result and the band structure calculation indicate that the strong Te 5p-Te 5p hybridization between the IrTe2 triangular lattice layers is responsible for the three-dimensionality of the Fermi surfaces and the intervening of the Fermi surfaces observed by ARPES.Comment: 5 pages, 4 figure

Structural phase transition in IrTe2_2: A combined study of optical spectroscopy and band structure calculations

Ir$_{1-x}$Pt$_x$Te$_2$ is an interesting system showing competing phenomenon between structural instability and superconductivity. Due to the large atomic numbers of Ir and Te, the spin-orbital coupling is expected to be strong in the system which may lead to nonconventional superconductivity. We grew single crystal samples of this system and investigated their electronic properties. In particular, we performed optical spectroscopic measurements, in combination with density function calculations, on the undoped compound IrTe$_2$ in an effort to elucidate the origin of the structural phase transition at 280 K. The measurement revealed a dramatic reconstruction of band structure and a significant reduction of conducting carriers below the phase transition. We elaborate that the transition is not driven by the density wave type instability but caused by the crystal field effect which further splits/separates the energy levels of Te (p$_x$, p$_y$) and Te p$_z$ bands.Comment: 16 pages, 5 figure

Charge-Stripe Order and Superconductivity in Ir1−xPtxTe2\mathrm{Ir_{1-x}Pt_xTe_2}

A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in $\mathrm{Ir_{1-x}Pt_xTe_2}$, as a function of Pt substitution and externally applied hydrostatic pressure, is presented. Experiments are focused on samples near the critical composition $x_c\sim 0.045$ where competition and switching between charge order and superconductivity is established. We show that charge order as a function of pressure in $\mathrm{Ir_{0.95}Pt_{0.05}Te_{2}}$ is preempted - and hence triggered - by a structural transition. Charge ordering appears uniaxially along the short crystallographic (1,0,1) domain axis with a $\mathrm{(\frac{1}{5},0,\frac{1}{5})}$ modulation. Based on these results we draw a charge-order phase diagram and discuss the relation between stripe ordering and superconductivity.Comment: 8 pages, 4 figures: Accepted in Scientific Report

Effects of Art from the Heart on Nurse Satisfaction and Patient Well-Being

Introduction. Art programs have been shown to positively affect unit culture, quality of care, and nursing practices. Art interventions improve well-being, reduce stress, and enhance nurse-patient communication. Art from the Heart (AFTH) is an art program that provides art supplies, visual art, and patient About Me pages to patients, families and employees at University of Vermont Medical Center (UVMMC).Objective. Assess the efficacy of AFTH through nursing staff perceptions, understanding, and attitudes toward the program.Methods. Structured interviews were conducted on Baird 4, an adult inpatient ward, at UVMMC. A 19-question survey using Likert scales and short answer formats was administered to nursing staff. Questions assessed perceptions of effects of art on patient anxiety and pain, communication, and job satisfaction. Surveys were analyzed to extract major and minor themes.Results. Twenty-eight interviews were obtained and two major themes emerged: nurse satisfaction and patient well-being. Nursing staff satisfaction minor themes included improved productivity, promoting conversation, and creating a positive influence on the unit. Respondents reported that AFTH helped initiate conversations with patients (100% of respondents) and reduced workday stress (68%). The second major theme, patient well-being, included benefits to patients with dementia, providing comfort, and serving as an outlet or distraction. Utilizing AFTH improved perceived patient mood (100%), health (78.5%), and reduced patient anxiety (89.3%).Conclusions. AFTH provides positive benefits by reducing nursing staff stress and perceived patient anxiety; improving communication, perceived patient mood and health; and creating a sense of community. AFTH should be expanded to the entire 6 Community Agency: Burlington City Arts, Art from the Hearthttps://scholarworks.uvm.edu/comphp_gallery/1240/thumbnail.jp