7,919 research outputs found
Phase Transition of Finite Size Quark Droplets with Isospin Chemical Potential in the Nanbu--Jona-Lasinio Model
Making use of the NJL model and the multiple reflection expansion
pproximation, we study the phase transition of the finite size droplet with u
and d quarks. We find that the dynamical masses of u, d quarks are different,
and the chiral symmetry can be restored at different critical radii for u, d
quark. It rovides a clue to understand the effective nucleon mass splitting in
nuclear matter. Meanwhile, it shows that the maximal isospin chemical potential
at zero temperature is much smaller than the mass of pion in free space.Comment: 12 pages, 3 figures. To appear in Physical Review
Optically Controlled Stochastic Jumps of Individual Gold Nanorod Rotary Motors
Brownian microparticles diffusing in optical potential energy landscapes
constitute a generic testbed for nonequilibrium statistical thermodynamics and
has been used to emulate a wide variety of physical systems, ranging from
Josephson junctions to Stirling engines. Here we demonstrate that it is
possible to scale down this approach to nanometric length-scales by
constructing a tilted washboard potential for the rotation of plasmonic gold
nanorods. The potential depth and tilt can be precisely adjusted by modulating
the light polarization. This allows for a gradual transition from continuous
rotation to discrete stochastic jumps, which are found to follow Kramers
dynamics in excellent agreement with stochastic simulations. The results widen
the possibilities for fundamental experiments in statistical physics and
provide new insights in how to construct light-driven nanomachines and
multifunctional sensing elements.Comment: 6 pages, 4 figure
Spin squeezing generated by the anisotropic central spin model
Spin squeezing, as a crucial quantum resource, plays a pivotal role in
quantum metrology, enabling us to achieve high-precision parameter estimation
schemes. Here we investigate the spin squeezing and the quantum phase
transition in an anisotropic central spin system. We find that this kind of
central spin systems can be mapped to the anisotropic Lipkin-Meshkov-Glick
model in the limit where the ratio of transition frequencies between the
central spin and the spin bath tends towards infinity. This property can induce
a one-axis twisting interaction and provides a new possibility for generating
spin squeezing. We separately consider generating spin-squeezed states via the
ground state and the dynamic evolution of the central spin model. The results
show that the spin squeezing parameter improves as the anisotropy parameter
decreases, and its value scales with system size as . Furthermore, we
obtain the critical exponent of the quantum Fisher information around the
critical point by numerical simulation, and find its value tends to as
the frequency ratio and the system size approach infinity. This work offers a
promising scheme for generating spin-squeezed state and paves the way for
potential advancements in quantum sensing.Comment: 10 pages, 4 figure
An overview of non-noble metal electrocatalysts and their associated air cathodes for Mg-air batteries
Abstract Although metal-air batteries (MABs) including Mg-air batteries possess high theoretical energy densities and are promising in energy storage systems, the poor performances and high cost of corresponding electrocatalysts and air cathodes significantly limit practical application. Based on this, the present review gives a summary of the recent progress in the development of cost effective non-noble metal electrocatalysts and their associated air cathodes for MABs, with a particular focus on Mg-air batteries including the aspects of corresponding catalyst synthesis and characterization, catalyzed oxygen reduction reaction (ORR) mechanism, air cathode fabrication and performance validation. The paper also provides an analysis on the issues that challenge the development of advanced electrocatalysts and the associated air cathodes for Mg-air batteries, as well as a discussion of potential research directions that may help resolve these issues and facilitate the practical application of Mg-air batteries
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