53 research outputs found
Anisotropic Superconducting Properties of Optimally Doped BaFe(AsP) under Pressure
Magnetic measurements on optimally doped single crystals of
BaFe(AsP) () with magnetic fields applied
along different crystallographic axes were performed under pressure, enabling
the pressure evolution of coherence lengths and the anisotropy factor to be
followed. Despite a decrease in the superconducting critical temperature, our
studies reveal that the superconducting properties become more anisotropic
under pressure. With appropriate scaling, we directly compare these properties
with the values obtained for BaFe(AsP) as a function of
phosphorus content.Comment: 5 pages, 3 figure
Pressure-induced and Composition-induced Structural Quantum Phase Transition in the Cubic Superconductor (Sr/Ca)_3Ir_4Sn_{13}
We show that the quasi-skutterudite superconductor Sr_3Ir_4Sn_{13} undergoes
a structural transition from a simple cubic parent structure, the I-phase, to a
superlattice variant, the I'-phase, which has a lattice parameter twice that of
the high temperature phase. We argue that the superlattice distortion is
associated with a charge density wave transition of the conduction electron
system and demonstrate that the superlattice transition temperature T* can be
suppressed to zero by combining chemical and physical pressure. This enables
the first comprehensive investigation of a superlattice quantum phase
transition and its interplay with superconductivity in a cubic charge density
wave system.Comment: 4 figures, 5 pages (excluding supplementary material). To be
published in Phys. Rev. Let
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Coherent control of the silicon-vacancy spin in diamond
Spin impurities in diamond have emerged as a promising building block in a wide range of solid-state-based quantum technologies. The negatively charged silicon-vacancy centre combines the advantages of its high-quality photonic properties with a ground-state electronic spin, which can be read out optically. However, for this spin to be operational as a quantum bit, full quantum control is essential. Here we report the measurement of optically detected magnetic resonance and the demonstration of coherent control of a single silicon-vacancy centre spin with a microwave field. Using Ramsey interferometry, we directly measure a spin coherence time, T2*, of 115±9 ns at 3.6 K. The temperature dependence of coherence times indicates that dephasing and decay of the spin arise from single-phonon-mediated excitation between orbital branches of the ground state. Our results enable the silicon-vacancy centre spin to become a controllable resource to establish spin-photon quantum interfaces.We acknowledge financial support by the University of Cambridge, the ERC Grant PHOENICS, FP7 Marie Curie Initial Training Networks S3NANO and SPIN NANO, and the NQIT programme. This research has been partially funded by the European Community’s Seventh Framework Programme (FP7/2007-2013) under Grant agreement no. 611143 (DIADEMS). B.P. thanks Wolfson College (Cambridge) for support through a Research Fellowship
Baseline characteristics of patients in the reduction of events with darbepoetin alfa in heart failure trial (RED-HF)
<p>Aims: This report describes the baseline characteristics of patients in the Reduction of Events with Darbepoetin alfa in Heart Failure trial (RED-HF) which is testing the hypothesis that anaemia correction with darbepoetin alfa will reduce the composite endpoint of death from any cause or hospital admission for worsening heart failure, and improve other outcomes.</p>
<p>Methods and results: Key demographic, clinical, and laboratory findings, along with baseline treatment, are reported and compared with those of patients in other recent clinical trials in heart failure. Compared with other recent trials, RED-HF enrolled more elderly [mean age 70 (SD 11.4) years], female (41%), and black (9%) patients. RED-HF patients more often had diabetes (46%) and renal impairment (72% had an estimated glomerular filtration rate <60 mL/min/1.73 m2). Patients in RED-HF had heart failure of longer duration [5.3 (5.4) years], worse NYHA class (35% II, 63% III, and 2% IV), and more signs of congestion. Mean EF was 30% (6.8%). RED-HF patients were well treated at randomization, and pharmacological therapy at baseline was broadly similar to that of other recent trials, taking account of study-specific inclusion/exclusion criteria. Median (interquartile range) haemoglobin at baseline was 112 (106–117) g/L.</p>
<p>Conclusion: The anaemic patients enrolled in RED-HF were older, moderately to markedly symptomatic, and had extensive co-morbidity.</p>
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