800,924 research outputs found
A hidden constant in the anomalous Hall effect of a high-purity magnet MnSi
Measurements of the Hall conductivity in MnSi can provide incisive tests of
theories of the anomalous Hall (AH) effect, because both the mean-free-path and
magnetoresistance (MR) are unusually large for a ferromagnet. The large MR
provides an accurate way to separate the AH conductivity from
the ordinary Hall conductivity . Below the Curie temperature
, is linearly proportional to (magnetization) with a
proportionality constant that is independent of both and . In
particular, remains a constant while changes by a factor
of 100 between 5 K and . We discuss implications of the hidden constancy
in .Comment: 5 pages, 4 figures. Minor change
Weak-Light, Zero to -\pi Lossless Kerr-Phase Gate in Quantum-well System via Tunneling Interference Effect
We examine a Kerr phase gate in a semiconductor quantum well structure based
on the tunnelling interference effect. We show that there exist a specific
signal field detuning, at which the absorption/amplification of the probe field
will be eliminated with the increase of the tunnelling interference.
Simultaneously, the probe field will acquire a -\pi phase shift at the exit of
the medium. We demonstrate with numerical simulations that a complete 180^\circ
phase rotation for the probe field at the exit of the medium is achieved, which
may result in many applications in information science and telecommunication
The Strong Coupling Limit of the Scaling Function from the Quantum String Bethe Ansatz
Using the quantum string Bethe ansatz we derive the one-loop energy of a
folded string rotating with angular momenta (S,J) in AdS_3 x S^1 inside AdS_5 x
S^5 in the limit 1 << J << S, z=\lambda^(1/2) log(S/J) /(\pi J) fixed. The
one-loop energy is a sum of two contributions, one originating from the
Hernandez-Lopez phase and another one being due to spin chain finite size
effects. We find a result which at the functional level exactly matches the
result of a string theory computation. Expanding the result for large z we
obtain the strong coupling limit of the scaling function for low twist, high
spin operators of the SL(2) sector of N=4 SYM. In particular we recover the
famous -3 log(2)/\pi. Its appearance is a result of non-trivial cancellations
between the finite size effects and the Hernandez-Lopez correction.Comment: 18 pages, one figure, v2: footnote changed, v3: reference added, typo
correcte
Adiabatic passage of collective excitations in atomic ensembles
We describe a theoretical scheme that allows for transfer of quantum states
of atomic collective excitation between two macroscopic atomic ensembles
localized in two spatially-separated domains. The conception is based on the
occurrence of double-exciton dark states due to the collective destructive
quantum interference of the emissions from the two atomic ensembles. With an
adiabatically coherence manipulation for the atom-field couplings by stimulated
Ramann scattering, the dark states will extrapolate from an exciton state of an
ensemble to that of another. This realizes the transport of quantum information
among atomic ensembles.Comment: 7 pages, 2 figure
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