15,648 research outputs found
Majorana Fermion Induced Resonant Andreev Reflection
We describe experimental signatures of Majorana fermion edge states, which
form at the interface between a superconductor and the surface of a topological
insulator. If a lead couples to the Majorana fermions through electron
tunneling, the Majorana fermions induce \textit{resonant} Andreev reflections
from the lead to the grounded superconductor. The linear tunneling conductance
is () if there is an even (odd) number of vortices in the
superconductor. Similar resonance occurs for tunneling into the zero mode in
the vortex core. We also study the current and noise of a two-lead device.Comment: 4 pages, 3 figures. Discussion on STM tunneling into the Majorana
zero mode in the vortex core is adde
Magnetoconductivity in Weyl semimetals: Effect of chemical potential and temperature
We present the detailed analyses of magneto-conductivities in a Weyl
semimetal within Born and self-consistent Born approximations. In the presence
of the charged impurities, the linear magnetoresistance can happen when the
charge carriers are mainly from the zeroth (n=0) Landau level. Interestingly,
the linear magnetoresistance is very robust against the change of temperature,
as long as the charge carriers mainly come from the zeroth Landau level. We
denote this parameter regime as the high-field regime. On the other hand, the
linear magnetoresistance disappears once the charge carriers from the higher
Landau levels can provide notable contributions. Our analysis indicates that
the deviation from the linear magnetoresistance is mainly due to the deviation
of the longitudinal conductivity from the behavior. We found two
important features of the self-energy approximation: 1. a dramatic jump of
, when the Landau level begins to contribute charge
carriers, which is the beginning point of the middle-field regime, when
decreasing the external magnetic field from high field; 2. In the low-field
regime shows a behavior and results the
magnetoresistance to show a behavior. The detailed and
careful numerical calculation indicates that the self-energy approximation
(including both the Born and the self-consistent Born approximations) does not
explain the recent experimental observation of linear magnetoresistance in Weyl
semimetals.Comment: The accepted version. Extending the previous version by including the
discussions of self-consistent Born approximatio
Selective Equal-Spin Andreev Reflections Induced by Majorana Fermions
In this work, we find that Majorana fermions induce selective equal spin
Andreev reflections (SESARs), in which incoming electrons with certain spin
polarization in the lead are reflected as counter propagating holes with the
same spin. The spin polarization direction of the electrons of this Andreev
reflected channel is selected by the Majorana fermions. Moreover, electrons
with opposite spin polarization are always reflected as electrons with
unchanged spin. As a result, the charge current in the lead is spin-polarized.
Therefore, a topological superconductor which supports Majorana fermions can be
used as a novel device to create fully spin-polarized currents in paramagnetic
leads. We point out that SESARs can also be used to detect Majorana fermions in
topological superconductors.Comment: 5 pages, 3 figures. Comments are welcome. Title changed to match
published versio
Sewage Pollution In Kelang River and its Estuary
High faecal coliform counts detected in Kelang River reveal that the River is being heavily polluted
by domestic sewage discharge. The average faecal coliform counts in water from Stations I, II, III, IV, V
and VI were 113/100 ml, 1 x 106 /100 ml, 1 x 105 /100 ml, 1.6 x 106 /100 ml, 5.8 x 103 /100 ml and
260/100 ml respectively. As compared to the WHO recommended guide limit of100 faecal califorms/100 ml
for bathing water, counts in all stations except Station I were much higher than the recommended limit.
The average concentration of faecal coliforms in sediment of Stations I, II, III and IV were 17.9/g,
1 x 104 /g, 3.2 x 104 /g and 1.6 x 104 /g respectively. The faecal coliform coun ts at the estuary ofKelang
River were much lower than those of the coastal waters of Penang and Johore. The reason is not clear.
Most probably the suspended solids play an important role in the disappearance of faecal coliforms in the
estuary
Robustness of Majorana Fermion induced Fractional Josephson Effect
It is shown in previous works that the coupling between two Majorana end
states in superconducting quantum wires leads to fractional Josephson effect.
However, in realistic experimental conditions, multiple bands of the wires are
occupied and the Majorana end states are accompanied by other fermionic end
states. This raises the question concerning the robustness of fractional
Josephson effect in these situations. In this work, we show that the absence of
the avoided energy crossing which gives rise to the fractional Josephson effect
is robust, even when the Majorana fermions are coupled with arbitrary strengths
to other fermions. Moreover, we calculate the temperature dependence of the
fractional Josephson current and show that it is suppressed by thermal
excitations to the other fermion bound states.Comment: 4+ pages, 3 figure
Probing Non-Abelian Statistics in nu=12/5 Quantum Hall State
The tunneling current and shot noise of the current between two Fractional
Quantum Hall (FQH) edges in the FQH state in electronic
Mach-Zehnder interferometer are studied. It is shown that the tunneling current
and shot noise can be used to probe the existence of parafermion
statistics in the FQH state. More specifically, the dependence of
the current on the Aharonov-Bohm flux in the Read-Rezayi state is asymmetric
under the change of the sign of the applied voltage. This property is absent in
the Abelian Laughlin states. Moreover the Fano factor can exceed 12.7 electron
charges in the FQH state . This number well exceeds the maximum
possible Fano factor in all Laughlin states and the Moore-Read
state which was shown previously to be and respectively.Comment: 10 pages, 6 figure
Well-Posedness And Accuracy Of The Ensemble Kalman Filter In Discrete And Continuous Time
The ensemble Kalman filter (EnKF) is a method for combining a dynamical model
with data in a sequential fashion. Despite its widespread use, there has been
little analysis of its theoretical properties. Many of the algorithmic
innovations associated with the filter, which are required to make a useable
algorithm in practice, are derived in an ad hoc fashion. The aim of this paper
is to initiate the development of a systematic analysis of the EnKF, in
particular to do so in the small ensemble size limit. The perspective is to
view the method as a state estimator, and not as an algorithm which
approximates the true filtering distribution. The perturbed observation version
of the algorithm is studied, without and with variance inflation. Without
variance inflation well-posedness of the filter is established; with variance
inflation accuracy of the filter, with resepct to the true signal underlying
the data, is established. The algorithm is considered in discrete time, and
also for a continuous time limit arising when observations are frequent and
subject to large noise. The underlying dynamical model, and assumptions about
it, is sufficiently general to include the Lorenz '63 and '96 models, together
with the incompressible Navier-Stokes equation on a two-dimensional torus. The
analysis is limited to the case of complete observation of the signal with
additive white noise. Numerical results are presented for the Navier-Stokes
equation on a two-dimensional torus for both complete and partial observations
of the signal with additive white noise
Zero-bias peaks in spin-orbit coupled superconducting wires with and without Majorana end-states
One of the simplest proposed experimental probes of a Majorana bound-state is
a quantized (2e^2/h) value of zero-bias tunneling conductance. When temperature
is somewhat larger than the intrinsic width of the Majorana peak, conductance
is no longer quantized, but a zero-bias peak can remain. Such a non-quantized
zero-bias peak has been recently reported for semiconducting nanowires with
proximity induced superconductivity. In this paper we analyze the relation of
the zero-bias peak to the presence of Majorana end-states, by simulating the
tunneling conductance for multi-band wires with realistic amounts of disorder.
We show that this system generically exhibits a (non-quantized) zero-bias peak
even when the wire is topologically trivial and does not possess Majorana
end-states. We make comparisons to recent experiments, and discuss the
necessary requirements for confirming the existence of a Majorana state.Comment: 5 pages, 4 Figure
Petroleum Hydrocarbon along the Coastal Areas of Port Dickson
The petroleum hydrocarbon content in water and sand along the coast of Port Dickson was studied between
December 1984 and November 1985. The mean and range of petroleum hydrocarbon in water were 32.24
ppb and 2.52-73.34 ppb respectively, while for the sand, the range was between 2.1 and 70.4 mg/kg d1)1 sand.
A pronounced fluctuation of hydrocarbon level in water with sampling date was detected at the sampling
stations during the sampling period. The results indicated that the coastal area of Port Dickson carried some
degree of hydrocarbon pollution
Sewage Pollution in the Coastal Waters off Port Dickson, Straits of Malacca
The distribution of fecal colifonn bacteria in the near-shore waters and coastal waters of Port Dickson was studied
between August 1987 and August 1989. Although a significantly high level of fecal coliform bacteria was found
in the near- shore waters, very low levels were detected in the sediments and in roastal waters between 0.5 km and 5
kIn away from the roast. The results indirate that the coastal waters of Port Dickson are suitable for recreational and aquaculture uses
- …