81 research outputs found
The formation of 3,6-diphenylpyridazine and 2,5-diphenylpyrrole from alpha-styryl azide
Formation of 3,6-diphenylpyridazine and 2,5- diphenylpyrrole from alpha-styryl azid
Acid catalyzed reactions of alpha and beta styryl azides
Acid degradation of alpha and beta styryl azide
Josephson Effect in Fulde-Ferrell-Larkin-Ovchinnikov Superconductors
Due to the difference in the momenta of the superconducting order parameters,
the Josephson current in a Josephson junction between a
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor and a conventional BCS
superconductor is suppressed. We show that the Josephson current may be
recovered by applying a magnetic field in the junction. The field strength and
direction at which the supercurrent recovery occurs depend upon the momentum
and structure of the order parameter in the FFLO state. Thus the Josephson
effect provides an unambiguous way to detect the existence of an FFLO state,
and to measure the momentum of the order parameter.Comment: 4 pages with one embedded eps figur
Supercooling of the disordered vortex lattice in Bi_2Sr_2CaCu_2O_8+d
Time-resolved local induction measurements near to the vortex lattice
order-disorder transition in optimally doped
BiSrCaCuO single crystals shows that the
high-field, disordered phase can be quenched to fields as low as half the
transition field. Over an important range of fields, the electrodynamical
behavior of the vortex system is governed by the co-existence of the two phases
in the sample. We interpret the results in terms of supercooling of the
high-field phase and the possible first order nature of the order-disorder
transition at the ``second peak''.Comment: 4 pages, 3 figures. Submitted to Nature, July 10th, 1999; Rejected
August 8th for lack of broad interest Submitted to Physical Review Letters
September 10th, 199
Color Superconductivity in Compact Stars
After a brief review of the phenomena expected in cold dense quark matter,
color superconductivity and color-flavor locking, we sketch some implications
of recent developments in our understanding of cold dense quark matter for the
physics of compact stars. We give a more detailed summary of our recent work on
crystalline color superconductivity and the consequent realization that (some)
pulsar glitches may originate in quark matter.Comment: 19 pages. 2 figures. To appear in the proceedings of the ECT Workshop
on Neutron Star Interiors, Trento, Italy, June 2000. Shorter versions
contributed to the proceedings of Strong and Electroweak Matter 2000,
Marseille, France, June 2000 and to the proceedings of Strangeness 2000,
Berkeley, CA, July 2000. KR was the speaker at all three meeting
Crystalline Color Superconductivity
In any context in which color superconductivity arises in nature, it is
likely to involve pairing between species of quarks with differing chemical
potentials. For suitable values of the differences between chemical potentials,
Cooper pairs with nonzero total momentum are favored, as was first realized by
Larkin, Ovchinnikov, Fulde and Ferrell (LOFF). Condensates of this sort
spontaneously break translational and rotational invariance, leading to gaps
which vary periodically in a crystalline pattern. Unlike the original LOFF
state, these crystalline quark matter condensates include both spin zero and
spin one Cooper pairs. We explore the range of parameters for which crystalline
color superconductivity arises in the QCD phase diagram. If in some shell
within the quark matter core of a neutron star (or within a strange quark star)
the quark number densities are such that crystalline color superconductivity
arises, rotational vortices may be pinned in this shell, making it a locus for
glitch phenomena.Comment: 40 pages, LaTeX with eps figs. v2: New paragraph on Ginzburg-Landau
treatment of LOFF phase in section 5. References added. v3: Small changes
only. Version to appear in Phys. Rev.
Fulde-Ferrell-Larkin-Ovchinnikov State in Heavy Fermion Superconductors
The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is a novel superconducting
state in a strong magnetic field characterized by the formation of Cooper pairs
with nonzero total momentum (k \uparrow, -k+q \downarrow), instead of the
ordinary BCS pairs (k \uparrow, -k \downarrow). A fascinating aspect of the
FFLO state is that it exhibits inhomogeneous superconducting phases with a
spatially oscillating order parameter and spin polarization. The FFLO state has
been of interest in various research fields, not only in superconductors in
solid state physics, but also in neutral Fermion superfluid of ultracold atomic
gases and in color superconductivity in high energy physics. In spite of
extensive studies of various superconductors, there has been no undisputed
experimental verification of the FFLO state, mainly because of the very
stringent conditions required of the superconducting materials. Among several
classes of materials, certain heavy fermion and organic superconductors are
believed to provide conditions that are favorable to the formation of the FFLO
state. This review presents recent experimental and theoretical developments of
the FFLO state mainly in heavy fermion superconductors. In particular we
address the recently discovered quasi-two-dimensional superconductor CeCoIn_5,
which is a strong candidate for the formation of the FFLO state.Comment: 17 pages, 12 figures with jpsf2.cls, to be published in J. Phys. Soc.
Jpn. (Special Topics - Frontiers of Novel Superconductivity in Heavy Fermion
Compounds
Inhomogeneous Superconductivity in Condensed Matter and QCD
Inhomogeneous superconductivity arises when the species participating in the
pairing phenomenon have different Fermi surfaces with a large enough
separation. In these conditions it could be more favorable for each of the
pairing fermions to stay close to its Fermi surface and, differently from the
usual BCS state, for the Cooper pair to have a non zero total momentum. For
this reason in this state the gap varies in space, the ground state is
inhomogeneous and a crystalline structure might be formed. This situation was
considered for the first time by Fulde, Ferrell, Larkin and Ovchinnikov, and
the corresponding state is called LOFF. The spontaneous breaking of the space
symmetries in the vacuum state is a characteristic feature of this phase and is
associated to the presence of long wave-length excitations of zero mass. The
situation described here is of interest both in solid state and in elementary
particle physics, in particular in Quantum Chromo-Dynamics at high density and
small temperature. In this review we present the theoretical approach to the
LOFF state and its phenomenological applications using the language of the
effective field theories.Comment: RevTex, 83 pages, 26 figures. Submitted to Review of Modern Physic
Superconducting phases of f-electron compounds
Intermetallic compounds containing f-electron elements display a wealth of
superconducting phases, that are prime candidates for unconventional pairing
with complex order parameter symmetries. For instance, superconductivity has
been found at the border of magnetic order as well as deep within ferro- and
antiferromagnetically ordered states, suggesting that magnetism may promote
rather than destroy superconductivity. Superconductivity near valence
transitions, or in the vicinity of magneto-polar order are candidates for new
superconductive pairing interactions such as fluctuations of the conduction
electron density or the crystal electric field, respectively. The experimental
status of the study of the superconducting phases of f-electron compounds is
reviewed.Comment: Rev. Mod. Phys. in print; 75 pages, 23 figures; comments welcom
Mapping the Conformational Dynamics and Pathways of Spontaneous Steric Zipper Peptide Oligomerization
The process of protein misfolding and self-assembly into various, polymorphic aggregates is associated with a number of important neurodegenerative diseases. Only recently, crystal structures of several short peptides have provided detailed structural insights into -sheet rich aggregates, known as amyloid fibrils. Knowledge about early events of the formation and interconversion of small oligomeric states, an inevitable step in the cascade of peptide self-assembly, however, remains still limited
- …