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 $N^{-2/3}$. Furthermore, we obtain the critical exponent of the quantum Fisher information around the critical point by numerical simulation, and find its value tends to $4/3$ 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