379 research outputs found
Possible Microscopic Doping Mechanism in Tl-2201
X-ray absorption spectroscopy on oxygen-annealed, self-flux-grown single
crystals of Tl-2201 suggests a microscopic doping mechanism whereby
interstitial oxygens are attracted to copper substituted on the thallium site,
contributing holes to both the planes and to these coppers, and typically
promoting only one hole to the plane rather than two. These copper substituents
would provide an intrinsic hole doping. The evidence for this is discussed,
along with an alternative interpretation.Comment: 2 pages, 1 figure, submitted as conference proceedings for M2S-IX,
Toky
An 8-month longitudinal exploration of body image and disordered eating in the UK during the COVID-19 pandemic
Research suggests that the COVID-19 pandemic is negatively impacting mental health, with rates of eating disorder referrals in particular rising steeply during the pandemic. This study aimed to examine 8-month changes in body image and disordered eating during the COVID-19 pandemic, and explore whether any changes were moderated by gender, age, or eating disorder history. This study used a longitudinal survey design in which 587 adults living in the UK (85 % women; mean age = 32.87 years) completed assessments every two months over five timepoints from May/June 2020 to January/February 2021. Measures included body esteem, disordered eating, and psychological distress. Mixed effect models showed small but significant improvements in body esteem and disordered eating symptoms from May/June 2020 to January/February 2021. These improvements were independent of changes in psychological distress, and did not vary by gender, age or eating disorder history. Whilst poor body image and disordered eating may have been elevated in the early period of the pandemic, this study suggests improvements, rather than worsening, of these outcomes over time. This may reflect adaptation to this changing context
Probing momentum-dependent scattering in uniaxially stressed Sr2RuO4 through the Hall effect
Funding: The authors acknowledge the financial support of the Max Planck Society. A. P. M. and C. W. H. acknowledge the financial support of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—TRR 288–422213477 (project A10). N. K. is supported by a KAKENHI Grants-in-Aids for Scientific Research (Grants No. 17H06136, No. 18K04715, and No. 21H01033), and Core-to-Core Program (No. JPJSCCA20170002) from the Japan Society for the Promotion of Science (JSPS) and by a JST-Mirai Program (Grant No. JPMJMI18A3). H. M. L. N. acknowledges support from the Alexander von Humboldt Foundation through a Research Fellowship for Postdoctoral Researchers. Research in Dresden benefits from the environment provided by the DFG Cluster of Excellence ct.qmat (EXC 2147, project ID 390858940).The largest Fermi surface sheet of the correlated metal Sr2RuO4 can be driven through a Lifshitz transition between an electronlike and an open geometry by uniaxial stress applied along the [100] lattice direction. Here, we investigate the effect of this transition on the longitudinal resistivity ρxx and the Hall coefficient RH. ρxx(T), when Sr2RuO4 is tuned to this transition, is found to have a T2logT form, as expected for a Fermi liquid tuned to a Lifshitz transition. RH is found to become more negative as the Fermi surface transitions from an electronlike to an open geometry, opposite to general expectations from this change in topology. The magnitude of the change in RH implies that scattering changes throughout the Brillouin zone, not just at the point in k space where the transition occurs. In a model of orbital-dependent scattering, the electron-electron scattering rate on sections of Fermi surface with xy orbital weight is found to decrease dramatically.Publisher PDFPeer reviewe
Encapsulated Single Crystal Growth and Annealing of the High-Temperature Superconductor Tl-2201
Highly-perfect platelet single crystals of Tl_2Ba_2CuO_{6+d} (Tl-2201) were
grown by a self-flux technique. A novel encapsulation scheme allowed the
precursors to react prior to the sealing required to contain volatile thallium
oxides, and permitted the removal of melt at the conclusion of growth,
reproducibly producing high yields of clean crystals. The crystals were
annealed under well-controlled oxygen partial pressures, then characterised.
They have sharp superconducting transitions, narrow X-ray rocking curves and a
low 4% substitution of thallium by copper, all evidence of their high
perfection and homogeneity. The crystals are orthorhombic at most dopings, and
a previously unreported commensurate superlattice distortion is observed.Comment: 8 pages, 5 figures, submitted to Journal of Crystal Growt
Elastic Chain in a Random Potential: Simulation of the Displacement Function and Relaxation
We simulate the low temperature behaviour of an elastic chain in a random
potential where the displacements are confined to the {\it longitudinal}
direction ( parallel to ) as in a one dimensional charge density
wave--type problem. We calculate the displacement correlation function and the size dependent average square displacement
. We find that with
at short distances and at intermediate
distances. We cannot resolve the asymptotic long distance dependence of
upon . For the system sizes considered we find with . The exponent is in agreement
with the Random Manifold exponent obtained from replica calculations and the
exponent is consistent with an exact solution for the chain
with {\it transverse} displacements ( perpendicular to ).The
distribution of nearest distances between pinning wells and chain-particles is
found to develop forbidden regions.Comment: 19 pages of LaTex, 6 postscript figures available on request,
submitted to Journal of Physics A, MAJOR CHANGE
Geometric effects on T-breaking in p+ip and d+id superconductors
Superconducting order parameters that change phase around the Fermi surface
modify Josephson tunneling behavior, as in the phase-sensitive measurements
that confirmed order in the cuprates. This paper studies Josephson coupling
when the individual grains break time-reversal symmetry; the specific cases
considered are and , which may appear in SrRuO and
NaCoO(HO) respectively. -breaking order parameters
lead to frustrating phases when not all grains have the same sign of
time-reversal symmetry breaking, and the effects of these frustrating phases
depend sensitively on geometry for 2D arrays of coupled grains. These systems
can show perfect superconducting order with or without macroscopic
-breaking. The honeycomb lattice of superconducting grains has a
superconducting phase with no spontaneous breaking of but instead power-law
correlations. The superconducting transition in this case is driven by binding
of fractional vortices, and the zero-temperature criticality realizes a
generalization of Baxter's three-color model.Comment: 8 page
Situationally edited empathy: an effect of socio-economic structure on individual choice
Criminological theory still operates with deficient models of the offender as agent, and of social influences on the agent’s decision-making process. This paper takes one ‘emotion’, empathy, which is theoretically of considerable importance in influencing the choices made by agents; particularly those involving criminal or otherwise harmful action. Using a framework not of rational action, but of ‘rationalised action’, the paper considers some of the effects on individual psychology of social, economic, political and cultural structure. It is suggested that the climate-setting effects of these structures promote normative definitions of social situations which allow unempathic, harmful action to be rationalised through the situational editing of empathy. The ‘crime is normal’ argument can therefore be extended to include the recognition that the uncompassionate state of mind of the criminal actor is a reflection of the self-interested values which govern non-criminal action in wider society
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Normal State O 17 NMR Studies of Sr2RuO4 under Uniaxial Stress
The effects of uniaxial compressive stress on the normal state O17 nuclear-magnetic-resonance properties of the unconventional superconductor Sr2RuO4 are reported. The paramagnetic shifts of both planar and apical oxygen sites show pronounced anomalies near the nominal a-axis strain μaaμv that maximizes the superconducting transition temperature Tc. The spin susceptibility weakly increases on lowering the temperature below T≃10 K, consistent with an enhanced density of states associated with passing the Fermi energy through a van Hove singularity. Although such a Lifshitz transition occurs in the γ band formed by the Ru dxy states hybridized with in-plane O pπ orbitals, the large Hund's coupling renormalizes the uniform spin susceptibility, which, in turn, affects the hyperfine fields of all nuclei. We estimate this "Stoner" renormalization S by combining the data with first-principles calculations and conclude that this is an important part of the strain effect, with implications for superconductivity. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI
Free flux flow resistivity in strongly overdoped high-T_c cuprate; purely viscous motion of the vortices in semiclassical d-wave superconductor
We report the free flux flow (FFF) resistivity associated with a purely
viscous motion of the vortices in moderately clean d-wave superconductor
Bi:2201 in the strongly overdoped regime (T_c=16K) for a wide range of the
magnetic field in the vortex state. The FFF resistivity is obtained by
measuring the microwave surface impedance at different microwave frequencies.
It is found that the FFF resistivity is remarkably different from that of
conventional s-wave superconductors. At low fields (H<0.2H_c2) the FFF
resistivity increases linearly with H with a coefficient which is far larger
than that found in conventional s-wave superconductors. At higher fields, the
FFF resistivity increases in proportion to \sqrt H up to H_c2. Based on these
results, the energy dissipation mechanism associated with the viscous vortex
motion in "semiclassical" d-wave superconductors with gap nodes is discussed.
Two possible scenarios are put forth for these field dependence; the
enhancement of the quasiparticle relaxation rate and the reduction of the
number of the quasiparticles participating the energy dissipation in d-wave
vortex state.Comment: 9 pages 7 figures, to appear in Phys. Rev.
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