25,091 research outputs found
Non-Markovian effect on the quantum discord
We study the non-Markovian effect on the dynamics of the quantum discord by
exactly solving a model consisting of two independent qubits subject to two
zero-temperature non-Markovian reservoirs, respectively. Considering the two
qubits initially prepared in Bell-like or extended Werner-like states, we show
that there is no occurrence of the sudden death, but only instantaneous
disappearance of the quantum discord at some time points, in comparison to the
entanglement sudden death in the same range of the parameters of interest. It
implies that the quantum discord is more useful than the entanglement to
describe quantum correlation involved in quantum systems.Comment: 5 pages, 5 figure
Vacancy-tuned paramagnetic/ferromagnetic martensitic transformation in Mn-poor Mn_{1-x}CoGe alloys
It is shown that a temperature window between the Curie temperatures of
martensite and austenite phases around the room temperature can be obtained by
a vacancy-tuning strategy in Mn-poor Mn1-xCoGe alloys (0 <= x <= 0.050). Based
on this, a martensitic transformation from paramagnetic austenite to
ferromagnetic martensite with a large magnetization difference can be realized
in this window. This gives rise to a magnetic-field-induced martensitic
transformation and a large magnetocaloric effect in the Mn1-xCoGe system. The
decrease of the transformation temperature and of the thermal hysteresis of the
transformation, as well as the stable Curie temperatures of martensite and
austenite, are discussed on the basis of the Mn-poor Co-vacancy structure and
the corresponding valence-electron concentration.Comment: Manuscript revised. 18 pages, 6 figures and 1 table. Submitted for
publication
On a Cahn--Hilliard--Darcy system for tumour growth with solution dependent source terms
We study the existence of weak solutions to a mixture model for tumour growth
that consists of a Cahn--Hilliard--Darcy system coupled with an elliptic
reaction-diffusion equation. The Darcy law gives rise to an elliptic equation
for the pressure that is coupled to the convective Cahn--Hilliard equation
through convective and source terms. Both Dirichlet and Robin boundary
conditions are considered for the pressure variable, which allows for the
source terms to be dependent on the solution variables.Comment: 18 pages, changed proof from fixed point argument to Galerkin
approximatio
Resolving and Tuning Mechanical Anisotropy in Black Phosphorus via Nanomechanical Multimode Resonance Spectromicroscopy
Black phosphorus (P) has emerged as a layered semiconductor with a unique
crystal structure featuring corrugated atomic layers and strong in-plane
anisotropy in its physical properties. Here, we demonstrate that the crystal
orientation and mechanical anisotropy in free-standing black P thin layers can
be precisely determined by spatially resolved multimode nanomechanical
resonances. This offers a new means for resolving important crystal orientation
and anisotropy in black P device platforms in situ beyond conventional optical
and electrical calibration techniques. Furthermore, we show that
electrostatic-gating-induced straining can continuously tune the mechanical
anisotropic effects on multimode resonances in black P electromechanical
devices. Combined with finite element modeling (FEM), we also determine the
Young's moduli of multilayer black P to be 116.1 and 46.5 GPa in the zigzag and
armchair directions, respectively.Comment: Main Text: 13 Pages, 4 Figures; Supplementary Information: 5 Pages, 2
Figures, 2 Table
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