7,937 research outputs found
Detection and Implications of a Time-reversal breaking state in underdoped Cuprates
We present general symmetry considerations on how a Time-reversal breaking
state may be detected by angle-resolved photoemission using circularly
polarized photons as has been proposed earlier. Results of recent experiments
utilizing the proposal in underdoped cuprates are analysed and found to be
consistent in their symmetry and magnitude with a theory of the Copper-Oxides.
These togather with evidence for a quantum critical point and marginal
Fermi-liquid properties near optimum doping suggest that a valid microscopic
theory of the phenomena in the cuprates has been found.Comment: A statement on detecting the Anyon state is added and some typos are
subtracte
Dielectric properties of Li2O-3B2O3 glasses
The frequency and temperature dependence of the dielectric constant and the
electrical conductivity of the transparent glasses in the composition
Li2O-3B2O3 (LBO) were investigated in the 100 Hz- 10 MHz frequency range. The
dielectric constant and the loss in the low frequency regime were electrode
material dependent. Dielectric and electrical relaxations were respectively
analyzed using the Cole-Cole and electric modulus formalisms. The dielectric
relaxation mechanism was discussed in the framework of electrode and charge
carrier (hopping of the ions) related polarization using generalized Cole-Cole
expression. The frequency dependent electrical conductivity was rationalized
using Jonscher's power law. The activation energy associated with the dc
conductivity was 0.80 \pm 0.02 eV, which was ascribed to the motion of Li+ ions
in the glass matrix. The activation energy associated with dielectric
relaxation was almost equal to that of the dc conductivity, indicating that the
same species took part in both the processes. Temperature dependent behavior of
the frequency exponent (n) suggested that the correlated barrier hopping model
was the most apposite to rationalize the electrical transport phenomenon in
Li2O-3B2O3 glasses. These glasses on heating at 933 K/10h resulted in the known
non-linear optical phase LiB3O5.Comment: 32 pages, 13 figure
Collective Modes in the Loop Current Ordered Phase of Cuprates
Recently two branches of weakly dispersive collective modes have been
discovered in under-doped cuprates by inelastic neutron scattering.
Polarization analysis reveals that the modes are magnetic excitations. They are
only visible for temperatures below the transition temperature to a broken
symmetry phase which was discovered earlier and their intensity increases as
temperature is further decreased. The broken symmetry phase itself has
symmetries consistent with ordering of orbital current loops within a unit-cell
without breaking translational symmetry. In order to calculate the collective
modes of such a state we add quantum terms to the Ashkin-Teller (AT) model with
which the classical loop current order has been described. We derive that the
mean field ground state of the quantum model is a product over all unit-cells
of linear combination of the four possible classical configurations of the loop
current order in each unit-cell. The collective modes are calculated by using a
generalized Holstein-Primakoff boson representation of orbital moment operators
and lead to three branches of gapped weakly dispersive collective modes. The
experimental results are consistent with the two lower energy branches; the
third mode is at a higher energy than looked for by present neutron scattering
experiments and might also be over-damped. Implications of the discovery of the
collective modes are discussed.Comment: 16 pages, 6 figure
Incidence of Cold Injury and Effects of Reduced Air Pressure in High Altitude Areas of the Himalayas
Data covering the three-year period, 1981-1984, from the forward area hospitals, receiving patients from units operating in high altitude areas of the Himalaya reveal an average admission of 247 and 171 cases of cold injury and effects of reduced air pressure respectively. Chillblain was the commonest (85.8%) form of cold injury and high altitude pulmonary oedema the commonest (76.2%) clinical syndrome in the hopoxia group. In both groups, the disease was mild in 61 per cent cases and severe in about 36 per cent
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