2,551 research outputs found
The role of critical current on point contact Andreev Reflection spectrum between a normal metal and a superconductor
The point contact spectrum between a normal metal and a superconductor often
shows unexpected sharp dips in the conductance at voltage values larger than
the superconducting energy gap. These dips are not predicted in the
Blonder-Tinkham-Klapwizk (BTK) theory, commonly used to analyse these contacts.
We present here a systematic study of these dips in a variety of contacts
between different combinations of a superconductor and a normal metal. From the
correlation between the characteristics of these dips with the contact area, we
can surmise that such dips are caused by the contact not being in the ballistic
limit. An analysis of the possible errors introduced while analysing such a
spectrum with the standard BTK model is also presented.Comment: 16 pages, PS, figure include
Anomalous Triple Gauge Vertices at the Large Hadron-Electron Collider
At a high energy collider, such as the Large Hadron-Electron Collider
(LHeC) which is being planned at CERN, one can access the vertex
exclusively in charged current events with a radiated photon, with no
interference from the vertex. We find that the azimuthal angle between
the jet and the missing momentum in each charged current event is a sensitive
probe of anomalous couplings, and show that for quite reasonable
values of integrated luminosity, the LHeC can extend the discovery reach for
these couplings beyond all present experimental bounds.Comment: 11 pages, LaTeX2e, 5 EPS figure
On a Raychaudhuri equation for hot gravitating fluids
We generalize the Raychaudhuri equation for the evolution of a self
gravitating fluid to include an Abelian and non-Abelian hybrid magneto fluid at
a finite temperature. The aim is to utilize this equation for investigating the
dynamics of astrophysical high temperature Abelian and non-Abelian plasmas.Comment: 13 pages, Invited contribution to Pramana special issue dedicated to
A.K. Raychaudhuri, "The Raychaudhuri equation and its role in Modern
Cosmology". Pramana style files include
Localized reversible nanoscale phase separation in Pr_0.63Ca_0.37MnO_3 single crystal using a scanning tunneling microscope tip
We report the destabilization of the charge ordered insulating (COI) state in
a localized region of Pr_0.63Ca_0.37MnO_3 single crystal by current injection
using a scanning tunneling microscope tip. This leads to controlled phase
separation and formation of localized metallic nanoislands in the COI matrix
which have been detected by local tunneling conductance mapping. The metallic
regions thus created persist even after reducing the injected current to lower
values. The original conductance state can be restored by injecting a current
of similar magnitude but of opposite polarity. We thus achieve reversible
nanoscale phase separation that gives rise to the possibility to "write, read,
and erase" nanosized conducting regions in an insulating matrix with high
spatial resolution.Comment: 8 pages, 4 figures, Appl. Phys. Lett (accepted for publication
Direct observation of large temperature fluctuations during DNA thermal denaturation
In this paper we report direct measurement of large low frequency temperature
fluctuations in double stranded (ds) DNA when it undergoes thermal denaturation
transition. The fluctuation, which occurs only in the temperature range where
the denaturation occurs, is several orders more than the expected equilibrium
fluctuation. It is absent in single stranded (ss) DNA of the same sequence. The
fluctuation at a given temperature also depends on the wait time and vanishes
in a scale of few hours. It is suggested that the large fluctuation occurs due
to coexisting denaturated and closed base pairs that are in dynamic equilibrium
due to transition through a potential barrier in the scale of
25-30k_{B}T_{0}(T_{0}=300K).Comment: 4 pages, 5 figures, Replaced with revised versio
Singularity: Raychaudhuri Equation once again
I first recount Raychaudhuri's deep involvement with the singularity problem
in general relativity. I then argue that precisely the same situation has
arisen today in loop quantum cosmology as obtained when Raychaudhuri discovered
his celebrated equation. We thus need a new analogue of the Raychaudhuri
equation in quantum gravity.Comment: 11 pages, Contribution to Special issue of Pramana on Raychaudhuri
Equation at Cross-roads, edited by Naresh Dadhich, Pankaj Joshi and Probir
Ro
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