3,190 research outputs found
Coherent matter waves emerging from Mott-insulators
We study the formation of (quasi-)coherent matter waves emerging from a Mott
insulator for strongly interacting bosons on a one-dimensional lattice. It has
been shown previously that a quasi-condensate emerges at momentum k=\pi/2a,
where a is the lattice constant, in the limit of infinitely strong repulsion
(hard-core bosons). Here we show that this phenomenon persists for all values
of the repulsive interaction that lead to a Mott insulator at a commensurate
filling. The non-equilibrium dynamics of hard-core bosons is treated exactly by
means of a Jordan-Wigner transformation, and the generic case is studied using
a time-dependent density matrix renormalization group technique. Different
methods for controlling the emerging matter wave are discussed.Comment: 20 pages, 11 figures. Published versio
New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn
We report the discovery of new superconducting and novel magnetic phases in
CeIn on the verge of antiferromagnetism (AFM) under pressure () through
the In-nuclear quadrupole resonance (NQR) measurements. We have found a
-induced phase separation of AFM and paramagnetism (PM) without any trace
for a quantum phase transition in CeIn. A new type of superconductivity
(SC) was found in GPa to coexist with AFM that is magnetically
separated from PM where the heavy fermion SC takes place. We propose that the
magnetic excitations such as spin-density fluctuations induced by the
first-order magnetic phase transition might mediate attractive interaction to
form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp
Soft x-ray magnetic circular dichroism study of weakly ferromagnetic ZnVO thin film
We performed a soft x-ray magnetic circular dichroism (XMCD) study of a
ZnVO thin film which showed small ferromagnetic moment. Field and
temperature dependences of V 2 XMCD signals indicated the coexistence of
Curie-Weiss paramagnetic, antiferromagnetic, and possibly ferromagnetic V ions,
quantitatively consistent with the magnetization measurements. We attribute the
paramagnetic signal to V ions substituting Zn sites which are somewhat
elongated along the c-axis
Parton Content of Real and Virtual Photons
Parameter-free and perturbatively stable leading order (LO) and
next-to-leading order (NLO) parton densities for real and virtual photons are
presented.Comment: Talk given at the International Conference on the Structure and
Interactions of the Photon, PHOTON99, Freiburg im Breisgau, Germany, May 23 -
27, 1999. To appear in the Proceedings, 5 page
Tomography increases key rates of quantum-key-distribution protocols
We construct a practically implementable classical processing for the BB84
protocol and the six-state protocol that fully utilizes the accurate channel
estimation method, which is also known as the quantum tomography. Our proposed
processing yields at least as high key rate as the standard processing by Shor
and Preskill. We show two examples of quantum channels over which the key rate
of our proposed processing is strictly higher than the standard processing. In
the second example, the BB84 protocol with our proposed processing yields a
positive key rate even though the so-called error rate is higher than the 25%
limit.Comment: 13 pages, 1 figure, REVTeX4. To be published in PRA. Version 2 adds
many references, a closed form key rate formula for unital channels, and a
procedure for the maximum likelihood channel estimatio
Genome Symbols in the Triticeae (Poaceae)
A system for the application of nuclear genome symbols in the tribe Triticeae is proposed. It is based mainly on prevailing symbols. In agreement with this, the system uses individual upper case letters as symbols in the first place. Since the number of basic nuclear genomes in the Triticeae exceeds the number of single letters in the Roman alphabet, some basic genomes are designated with an upper case letter followed by a lower case letter, e.g. Ns for the genome of Psathyrostachys. Superscripts in small letters are used when modified versions of a basic genome are referred to, e.g. HP for the genome found in Hordeum pusillum. Unknown or equivocally identified genomes are designated by X followed by a lower case letter, e.g. Xu for Hordeum murinum. Underline of the relevant genome symbol can be used to indicate the origin of the cytoplasm
Solution of the two impurity, two channel Kondo Model
We solve the two-impurity two-channel Kondo model using a combination of
conformal invariance and bosonisation techniques. The odd-even symmetric case
is analysed in detail. The RKKY interaction turns out to be exactly marginal,
resulting in a line of non-Fermi liquid fixed points. Explicit formulae are
given for the critical exponents and for the finite-size spectrum, which depend
continuously on a single parameter. The marginal line spans a range of values
of the RKKY coupling which goes from the infinitely strong ferromagnetic
point (associated with a 4-channel spin-1 Kondo model) to a finite
antiferromagnetic critical value beyond which a Fermi liquid is
recovered. We also find that, when the odd-even symmetry is broken, the
marginal line is unstable for ferromagnetic , while for antiferromagnetic
it extends into a manifold of fixed points.Comment: 9 pages, preprint LPTENS 94/1
The Search for Higher in Houston
It is a great pleasure to be invited to join the chorus on this auspicious
occasion to celebrate Professor K. Alex Mueller's 90th birthday by Professors
Annette Bussman-Holder, Hugo Keller, and Antonio Bianconi. As a student in high
temperature superconductivity, I am forever grateful to Professor Alex Mueller
and Dr. Georg Bednorz "for their important breakthrough in the discovery of
superconductivity in the ceramic materials" in 1986 as described in the
citation of their 1987 Nobel Prize in Physics. It is this breakthrough
discovery that has ushered in the explosion of research activities in high
temperature superconductivity (HTS) and has provided immense excitement in HTS
science and technology in the ensuing decades till now. Alex has not been
resting on his laurels and has continued to search for the origin of the
unusual high temperature superconductivity in cuprates.Comment: Dedicated to Alex Mueller, whose "important breakthrough in the
discovery of superconductivity in ceramic materials" in 1986 has changed the
world of superconductivit
Strong-Coupling Superconductivity of CeIrSi with the Non-centrosymmetric Crystal Structure
We studied the pressure-induced superconductor CeIrSi with the
non-centrosymmetric tetragonal structure under high pressure. The electrical
resistivity and ac heat capacity were measured in the same run for the same
sample. The critical pressure was determined to be = 2.25 GPa,
where the antiferromagnetic state disappears. The heat capacity
shows both antiferromagnetic and superconducting transitions at pressures close
to . On the other hand, the superconducting region is extended to
high pressures of up to about 3.5 GPa, with the maximum transition temperature
= 1.6 K around GPa. At 2.58 GPa, a large heat capacity
anomaly was observed at = 1.59 K. The jump of the heat capacity in
the form of is 5.7 0.1.
This is the largest observed value among previously reported superconductors,
indicating the strong-coupling superconductivity. The electronic specific heat
coefficient at is, however, approximately unchanged as a function
of pressure, even at .Comment: This paper will be published in J. Phys. Soc. Jpn. on the August
issue of 200
High-energy spectroscopic study of the III-V nitride-based diluted magnetic semiconductor GaMnN
We have studied the electronic structure of the diluted magnetic
semiconductor GaMnN ( = 0.0, 0.02 and 0.042) grown on Sn-doped
-type GaN using photoemission and soft x-ray absorption spectroscopy. Mn
-edge x-ray absorption have indicated that the Mn ions are in the
tetrahedral crystal field and that their valence is divalent. Upon Mn doping
into GaN, new state were found to form within the band gap of GaN, and the
Fermi level was shifted downward. Satellite structures in the Mn 2 core
level and the Mn 3 partial density of states were analyzed using
configuration-interaction calculation on a MnN cluster model. The deduced
electronic structure parameters reveal that the - exchange coupling in
GaMnN is stronger than that in GaMnAs.Comment: 6pages, 10figures. To be published to Phys. Rev.
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