304 research outputs found
CeCoIn5 - a quantum critical superfluid
We have made the first complete measurements of the London penetration depth
of CeCoIn5, a quantum-critical metal where superconductivity
arises from a non-Fermi-liquid normal state. Using a novel tunnel diode
oscillator designed to avoid spurious contributions to , we have
established the existence of intrinsic and anomalous power-law behaviour at low
temperature. A systematic analysis raises the possibility that the unusual
observations are due to an extension of quantum criticality into the
superconducting state.Comment: 5 pages, 3 figure
Phenomenology of a-axis and b-axis charge dynamics from microwave spectroscopy of highly ordered YBa2Cu3O6.50 and YBa2Cu3O6.993
Extensive measurements of the microwave conductivity of highly pure and
oxygen-ordered \YBCO single crystals have been performed as a means of
exploring the intrinsic charge dynamics of a d-wave superconductor. Broadband
and fixed-frequency microwave apparatus together provide a very clear picture
of the electrodynamics of the superconducting condensate and its thermally
excited nodal quasiparticles. The measurements reveal the existence of very
long-lived excitations deep in the superconducting state, as evidenced by sharp
cusp-like conductivity spectra with widths that fall well within our
experimental bandwidth. We present a phenomenological model of the microwave
conductivity that captures the physics of energy-dependent quasiparticle
dynamics in a d-wave superconductor which, in turn, allows us to examine the
scattering rate and oscillator strength of the thermally excited quasiparticles
as functions of temperature. Our results are in close agreement with the
Ferrell-Glover-Tinkham sum rule, giving confidence in both our experiments and
the phenomenological model. Separate experiments for currents along the and directions of detwinned crystals allow us to isolate the role
of the CuO chain layers in \YBCO, and a model is presented that incorporates
both one-dimensional conduction from the chain electrons and two-dimensional
transport associated with the \cuplane plane layers.Comment: 17 pages, 13 figure
The ‘hot zone policy’ for colorectal cancer screening presents unique risks and opportunities for rural Australia
Objective: Colorectal cancer has geographic inequities in Australia, with higher mortality rates and lower participation in the National Bowel Cancer Screening Program (NBCSP) in remote and rural areas. The at-home kit is temperaturesensitive, necessitating a ‘hot zone policy’ (HZP); kits are not sent when an area's average monthly temperature is above 30°C. Australians in HZP areas are susceptible to potential screening disruptions but may benefit from well-timed interventions to improve participation. This study describes the demographics of HZP areas and estimates the impacts of potential screening changes. Methods: The number of individuals in HZP areas was estimated, as well as correlations with remoteness, socio-economic and Indigenous status. The potential impacts of screening changes were estimated. Results: Over a million eligible Australians live in HZP areas, which are more likely to be remote/rural, have lower socio-economic status and higher Indigenous populations. Predictive modelling estimates that any 3-month screening disruption would increase CRC mortality rates up to 4.1 times more in HZP areas vs unaffected areas, while targeted intervention could decrease mortality rates 3.4 times more in HZP areas. Conclusion: People living in affected areas would be negatively impacted by any NBCSP disruption, compounding existing inequities. However, well-timed health promotion could have a stronger impact.Joachim Worthington, Jie-Bin Lew, Emily He, Kate Broun, Katina D'Onise, Paul Grogan, Karen Canfell, Eleonora Felett
Systematic behaviour of the in-plane penetration depth in d-wave cuprates
We report the temperature T and oxygen concentration dependences of the
penetration depth of grain-aligned YBa_2Cu_3O_{7-\delta} with \delta= 0.0, 0.3
and 0.43. The values of the in-plane \lambda_{ab}(0) and out-of-plane
\lambda_{c}(0) penetration depths, the low temperature linear term in
\lambda_{ab}(T), and the ratio \lambda_{c}(0) /\lambda_{ab}(T) were found to
increase with increasing . The systematic changes of the linear term in
\lambda_{ab}(T) with T_c found here and in recent work on HgBa_2Ca_{n-1}
Cu_nO_{2n+2+\delta} (n = 1 and 3) are discussed.Comment: 4 pages, 4 figure
Should I Take Aspirin? (SITA): RCT of a decision aid for cancer chemoprevention.
Background Australian guidelines recommend that all people aged 50-70 years old consider taking low-dose aspirin to reduce the risk of colorectal cancer (CRC). Aim To determine the effect of a consultation with a researcher in general practice using a decision aid about taking low-dose aspirin to prevent CRC on informed decision-making and low-dose aspirin uptake compared to a general CRC prevention brochure. Design and Setting Individually randomised controlled trial in six general practices in Victoria, Australia, from October 2020 to March 2021. Method Patients aged 50-70 years attending a general practitioner (GP) were recruited consecutively. The intervention was a consultation using a decision aid to discuss taking aspirin to reduce CRC risk; control consultations discussed reducing CRC risk generally. The self-reported co-primary outcomes were informed choices about taking aspirin at one month and low-dose aspirin uptake at six months. Results 261 participants (86% of eligible patients) were randomised into trial arms (129 intervention, 132 control). 17.7% (20/113) of intervention and 7.6% (9/118) control participants reported making an informed choice at one month, an estimated 9.1% (95% CI 0.29% to 18.5) between-arm difference in proportions [odds ratio (OR) 2.47 (97.5% CI:0.94 to 6.52) p=0.074]. The proportions of individuals who reported using aspirin at six months were: 10.2% (12/118) intervention vs 13.8% (16/116) control (estimated between-arm difference: -4.0% (95% CI: -13.5 to 5.5); [OR= 0.68 (97.5% CI:0.27 to 1.70), p= 0.692]. Conclusion The decision aid improved informed decision-making; but has little effect on long-term regular use of aspirin to reduce CRC risk
Non-Locality and Strong Coupling in the Heavy Fermion Superconductor CeCoIn: A Penetration Depth Study
We report measurements of the magnetic penetration depth in single
crystals of CeCoIn down to 0.14 K using a tunnel-diode based,
self-inductive technique at 28 MHz. While the in-plane penetration depth tends
to follow a power law, , the data are better
described as a crossover between linear ({\it T} ) and
quadratic ({\it T} ) behavior, with the
crossover temperature in the strong-coupling limit. The {\it c}-axis
penetration depth is linear in {\it T}, providing evidence
that CeCoIn is a {\it d}-wave superconductor with line nodes along the
{\it c}-axis. The different temperature dependences of and
rule out impurity effects as the source of .Comment: 4 pages, 3 figure
Microwave Spectroscopy of Thermally Excited Quasiparticles in YBa_2Cu_3O_{6.99}
We present here the microwave surface impedance of a high purity crystal of
measured at 5 frequencies between 1 and 75 GHz. This data
set reveals the main features of the conductivity spectrum of the thermally
excited quasiparticles in the superconducting state. Below 20 K there is a
regime of extremely long quasiparticle lifetimes, due to both the collapse of
inelastic scattering below and the very weak impurity scattering in the
high purity -grown crystal used in this study. Above 20 K, the
scattering increases dramatically, initially at least as fast as .Comment: 13 pages with 10 figures. submitted to Phys Rev
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