664,683 research outputs found
Mesoscopic Resistance Fluctuations in Cobalt Nanoparticles
We present measurements of mesoscopic resistance fluctuations in cobalt
nanoparticles and study how the fluctuations with bias voltage, bias
fingerprints, respond to magnetization reversal processes. Bias fingerprints
rearrange when domains are nucleated or annihilated. The domain-wall causes an
electron wavefunction phase-shift of . The phase-shift is not
caused by the Aharonov-Bohm effect; we explain how it arises from the
mistracking effect, where electron spins lag in orientation with respect to the
moments inside the domain-wall. Dephasing time in Co at is short,
, which we attribute to the strong magnetocrystalline
anisotropy.Comment: 5 pages 3 figs colou
A Rate-Splitting Based Bound-Approaching Transmission Scheme for the Two-User Symmetric Gaussian Interference Channel with Common Messages
This paper is concerned with a rate-splitting based transmission strategy for the two-user symmetric Gaussian interference channel that contains common messages only. Each transmitter encodes its common message into multiple layers by multiple codebooks that drawn from one separate code book, and transmits the superposition of the messages corresponding to these layers; each receiver decodes the messages from all layers of the two users successively. Two schemes are proposed for decoding order and optimal power allocation among layers respectively. With the proposed decoding order scheme, the sum-rate can be increased by rate-splitting, especially at the optimal number of rate-splitting, using average power allocation in moderate and weak interference regime. With the two proposed schemes at the receiver and the transmitter respectively, the sum-rate achieves the inner bound of HK without time-sharing. Numerical results show that the proposed optimal power allocation scheme with the proposed decoding order can achieve significant improvement of the performance over equal power allocation, and achieve the sum-rate within two bits per channel use (bits/channel use) of the sum capacity
Quantum-disordered slave-boson theory of underdoped cuprates
We study the stability of the spin gap phase in the U(1) slave-boson theory
of the t-J model in connection to the underdoped cuprates. We approach the spin
gap phase from the superconducting state and consider the quantum phase
transition of the slave-bosons at zero temperature by introducing vortices in
the boson superfluid. At finite temperatures, the properties of the bosons are
different from those of the strange metal phase and lead to modified gauge
field fluctuations. As a result, the spin gap phase can be stabilized in the
quantum critical and quantum disordered regime of the boson system. We also
show that the regime of quantum disordered bosons with the paired fermions can
be regarded as the strong coupling version of the recently proposed nodal
liquid theory.Comment: 5 pages, Replaced by the published versio
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