2,067 research outputs found
Exploring the fragile antiferromagnetic superconducting phase in CeCoIn5
CeCoIn5 is a heavy fermion Type-II superconductor which exhibits clear
indications of Pauli-limited superconductivity. A variety of measurements give
evidence for a transition at high magnetic fields inside the superconducting
state, when the field is applied either parallel to or perpendicular to the c
axis. When the field is perpendicular to the c axis, antiferromagnetic order is
observed on the high-field side of the transition, with a magnetic wavevector
of (q q 0.5), where q = 0.44 reciprocal lattice units. We show that this order
remains as the magnetic field is rotated out of the basal plane, but the
associated moment eventually disappears above 17 degrees, indicating that the
anomalies seen with the field parallel to the c axis are not related to this
magnetic order. We discuss the implications of this finding.Comment: Accepted Physical Review Letters, September 2010. 4 pages, 4 figure
Light elements in massive single and binary stars
We highlight the role of the light elements (Li, Be, B) in the evolution of
massive single and binary stars, which is largely restricted to a diagnostic
value, and foremost so for the element boron. However, we show that the boron
surface abundance in massive early type stars contains key information about
their foregoing evolution which is not obtainable otherwise. In particular, it
allows to constrain internal mixing processes and potential previous mass
transfer event for binary stars (even if the companion has disappeared). It may
also help solving the mystery of the slowly rotating nitrogen-rich massive main
sequence stars.Comment: 10 pages, 8 figures, to appear in proc. IAU-Symp. 268. C. Charbonnel
et al., eds
Multiband effects on beta-FeSe single crystals
We present the upper critical fields Hc2(T) and Hall effect in beta-FeSe
single crystals. The Hc2(T) increases as the temperature is lowered for field
applied parallel and perpendicular to (101), the natural growth facet of the
crystal. The Hc2(T) for both field directions and the anisotropy at low
temperature increase under pressure. Hole carriers are dominant at high
magnetic fields. However, the contribution of electron-type carriers is
significant at low fields and low temperature. Our results show that multiband
effects dominate Hc2(T) and electronic transport in the normal state
Topological Quantum Computing with Only One Mobile Quasiparticle
In a topological quantum computer, universal quantum computation is performed
by dragging quasiparticle excitations of certain two dimensional systems around
each other to form braids of their world lines in 2+1 dimensional space-time.
In this paper we show that any such quantum computation that can be done by
braiding identical quasiparticles can also be done by moving a single
quasiparticle around n-1 other identical quasiparticles whose positions remain
fixed.Comment: 4 pages, 5 figure
The Missing Link: Magnetism and Superconductivity
The effect of magnetic moments on superconductivity has long been a
controversial subject in condensed matter physics. While Matthias and
collaborators experimentally demonstrated the destruction of superconductivity
in La by the addition of magnetic moments (Gd), it has since been suggested
that magnetic fluctuations are in fact responsible for the development of
superconducting order in other systems. Currently this debate is focused on
several families of unconventional superconductors including high-Tc cuprates,
borocarbides as well as heavy fermion systems where magnetism and
superconductivity are known to coexist. Here we report a novel aspect of
competition and coexistence of these two competing orders in an interesting
class of heavy fermion compounds, namely the 1-1-5 series: CeTIn5 where T=Co,
Ir, or Rh. Our optical experiments indicate the existence of regions in
momentum space where local moments remain unscreened. The extent of these
regions in momentum space appears to control both the normal and
superconducting state properties in the 1-1-5 family of heavy fermion (HF)
superconductors.Comment: 6 pages, 2 figure
Enhanced Thermoelectric Power and Electronic Correlations in RuSe
We report the electronic structure, electric and thermal transport properties
of RuIrSe (). RuSe is a semiconductor that
crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe
exceeds -200 V/K around 730 K. Ir substitution results in the suppression
of the resistivity and the Seebeck coefficient, suggesting the removal of the
peaks in density of states near the Fermi level. RuIrSe
shows a semiconductor-metal crossover at about 30 K. The magnetic field
restores the semiconducting behavior. Our results indicate the importance of
the electronic correlations in enhanced thermoelectricity of RuSb.Comment: 6 pages, 4 figure
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