Nonextensive and extensive thermostatistic properties of Fermi systems trapped in different external potentials

The thermostatistic properties of a q-generalized Fermi system trapped in a generic power-law potential are studied, based on the generalized statistic distribution derived from the Tsallis entropy. The total number of particles, the total energy, and the heat capacity at constant volume of the system are derived. The thermostatistic characteristics of the system are discussed in detail. It is found that the thermostatistic properties of such a system depend closely on parameter q, dimensional number of the space, kinetic characteristics of particles and shapes of the external potential, and the external potential has a great influence on the thermostatistie properties of the system. Moreover, it is shown that the results obtained here are very general and can be used to unify the description of the nonextensive and extensive thermostatistie properties of a class of Fermi systems trapped in different external potentials so that the important conclusions of many typical Fermi systems in the literature may be directly derived from the present paper.

Sonic horizon dynamics of ultracold Fermi system under elongated harmonic potential

We study the phenomena of the sonic horizon in an ultracold atomic Fermi system in an elongated harmonic trap.Based on the one-dimensional Gross–Pitaevskii equation model and variational method combined with exact derivation approach, we derive an analytical formula which describes the occurrence of the sonic horizon and the associated Hawking radiation temperature. Using a pictorial demonstration of the key physical quantities we identify the features reported in prior numerical studies of a three-dimensional（3 D） ultracold atomic system, proving the applicability of the theoretical model presented here.

The stability of a non-extensive relativistic Fermi system

Based on the statistical theory of non-extensive relativity, and using theoretical analysis and numerical simulation, the non-extensive mechanical stability of ultra-relativistic free Fermi gas is investigated. The expressions of the stability conditions under high and low temperatures are given, and the mechanisms of the influences of temperature, ultra- relativistic effect, and non-extensive parameter q on stability are analysed. Our results show that at high temperature and under the condition of q 〈 1, the stability of a non-extensive system is weaker than that of an extensive system, and the relativistic effect reduces system stability as compared with a non-relativistic system. However, under the condition of q 〉 1, the stability of the non-extensive system is stronger than that of the extensive system, and the relativistic effect strengthens the system stability as compared with the non-relativistic system. In addition, under the condition of low temperature, the variation of the stability of the non-extensive system with temperature has a turning point.

Fermion System with Quantum Group Symmetry and Usual Fermion Realizations of S1_(q)(2)

The usual fermion realizations of quantum algebra S1_(q)(2) defining higher-dimensional representations are built in this letter.Using them,we construct a usual fermion system with quantum group symmetry of S1_(q)(2) as a q-deformation of the pairing correlation model in many-body problems.Its energy spectra are exactly solved out from the representation theory of S1_(q)(2).

LANDAUS FERMI LIQUID THEORY OF HEAVY-FERMION SUPERCONDUCTING SYSTEMS

We have established a relation between the parameters of periodic Anderson model Hamiltonian and the Landau's phenomenological paramerters,and applied it to heavy-fermion superconducting systems.The calculated results of specific heat coefficients and superconducting critical temperatures are in agreement with the experimental ones.The conclusion is that heavy-fermion superconducting systems induced by Fermi liquid interaction are P-wave type.

A FERMI LIQUID THEORY OF MIXED-VALENCE SYSTEMS

The local non-interacting Fermi liquid theory of News and Hewson is extended to include the interaction by introducing a molecular field parameter.The zero-temperature susceptibility and linear coefficient of specific heat are calculated.

Fermi Rubik's Cube in High-Pressure Induced Chlorine-Rich Compounds

In the quasi-free electron model,the Fermi surface spreads into a sphere in the Brillouin zone,i.e.,the Fermi sphere.The Fermi sphere exists widely in metal systems,no matter whether the crystal is in a body-center cubic,face-center cubic,or hexagonal close-packed lattice.Here,we report a class of compounds stabilized at high pressure with Rubik’s cubic Fermi surface.

Chiral Pair Density Waves with Residual Fermi Arcs in RbV_(3)Sb_(5)

The chiral 2×2 charge order has been reported and confirmed in the kagome superconductor RbV_(3)Sb_(5),while its interplay with superconductivity remains elusive owing to its lowest superconducting transition temperature Tc of about 0.85K in the AV_(3)Sb_(5) family(A=K,Rb,Cs)that severely challenges electronic spectroscopic probes.Here,utilizing dilution-refrigerator-based scanning tunneling microscopy down to 30 mK,we observe chiral 2×2 pair density waves with residual Fermi arcs in RbV_(3)Sb_(5).We find a superconducting gap of 150 μeV with substantial residual in-gap states.The spatial distribution of this gap exhibits chiral 2×2 modulations,signaling a chiral pair density wave(PDW).Our quasi-particle interference imaging of the zero-energy residual states further reveals arc-like patterns.We discuss the relation of the gap modulations with the residual Fermi arcs under the space-momentum correspondence between PDW and Bogoliubov Fermi states.

Fermi Surface Nesting with Heavy Quasiparticles in the Locally Noncentrosymmetric Superconductor CeRh_(2)As_(2)

The locally noncentrosymmetric heavy fermion superconductor CeRh_(2)As_(2) has attracted considerable interests due to its rich superconducting phases,accompanied by possible quadrupole density wave and pronounced antiferromagnetic excitations.To understand the underlying physics,here we report measurements from highresolution angle-resolved photoemission.Our results reveal fine splittings of the conduction bands related to the locally noncentrosymmetric structure,as well as a quasi-two-dimensional Fermi surface(FS)with strong 4f contributions.The FS shows signs of nesting with an in-plane vector q_(1)=(π/α,π/α),which is facilitated by the heavy bands nearˉ𝑋arising from the characteristic conduction-X hybridization.The FS nesting provides a natural explanation for the observed antiferromagnetic spin fluctuations at(π/α,π/α),which might be the driving force for its unconventional superconductivity.Our experimental results can be reasonably explained by density functional theory plus dynamical mean field theory calculations,which can capture the strong correlation effects.Our study not only provides spectroscopic signature of the key factors underlying the field-induced superconducting transition,but also uncovers the critical role of FS nesting and lattice Kondo effect in the underlying magnetic fluctuations.

根据Vrentas-Vrentas理论模拟小麦粉的水分吸附滞后:模型参数χ及k表示为Fermi函数的形式

水分吸附及其滞后现象广泛存在并对食品加工及食品品质具有重要影响。采用动态水蒸气吸附分析仪测定了小麦粉在3个温度条件下的吸湿、解吸平衡水分,然后基于Vrentas-Vrentas(VV)理论进行模拟分析。结果显示,小麦粉的水分吸附滞后程度随温度升高而减小,吸湿与解吸曲线在高水分区域重合,据此提出一个确定玻璃化转变水分的方法。不论吸湿还是解吸,其Flory-Huggins相互作用系数χ皆随水分体积分数而变化,本实验提出采用Peleg改进的Fermi函数表示这种关系。在根据吸湿的χ参数模拟解吸时,VV模型中的参数k随体积分数变化可以表示为Fermi函数的形式。

Topological superconductors with spin-triplet pairings and Majorana Fermi arcs

We construct a three-dimensional topological superconductor Bogoliubov–de Gennes(BdG)Hamiltonian with the normal state being a three-dimensional topological insulator.By introducing inter-orbital spin-triplet pairings term△3,there are topological Majorana nodes in the bulk and they are connected by Majorana Fermi arcs on the surface,similar to the case of Weyl semimetal.Furthermore,by adding an inversion-breaking term to the normal state,momentum-independent pairing terms with different parities can coexist in the Bd G Hamiltonian,which creates more Majorana modes similar to Andreev bound states and a richer phase diagram.

Optimal preparation of Bose and Fermi atomic gas mixtures of ^(87)Rb and ^(40)K in a crossed optical dipole trap

We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the ODT.We observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical trap.By optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the ODT.We experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are obtained.The ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.

贵金属修饰型TiO_2的催化活性及Fermi能级对其光催化性能的影响

采用自制纳米TiO_2粉末，以磷酸铝为粘结剂，制备了负载型TiO_2光催化剂。将Ag，Pt或Pd 3种金属的盐溶液滴涂在负载TiO_2的表面，从而得到修饰型负载光催化剂(M／TiO_2)。通过甲基橙溶液降解实验研究了贵金属的掺杂种类和含量对TiO_2光催化性能的影响。实验结果表明：适量掺杂Ag，Pt或Pd 3种金属粒子均可提高TiO_2的光催化活性，且3种金属粒子的最佳掺杂质量分数分别为0.5％，1.0％和1.0％。在最佳掺杂量时，Ag／TiO_2[ω(Ag)=0.5％]的光催化活性要高于Pt／TiO_2[ω(Pt)=1.0％]或Pd／TiO_2[ω(Pd)=1.0％]。另外，通过金属一半导体接触理论阐述了M／TiO_2的光催化机理，并通过Ag，Pt，Pd金属的Fermi能级的不同，解释了Ag／TiO_2，Pt／TiO_2和Pd／TiO_2 3种光催化剂催化性能的差别。

Fermi体系逆问题的一种新解法

利用加性Mobius级数反演方法,提出了解决Fermi体系逆问题的一类新方法;介绍了加性Mobius反演和一雏差分方程之间的联系。

Fermi耀变体红移和gamma射线谱指数特性研究

收集了368个具有gamma射线数据的高置信度Fermi耀变体(157个FSRQs和211个BL Lac天体),讨论了该样本的红移和gamma射线谱指数的分布特性,结果表明:HBLs的红移和gamma射线谱指数较小,FSRQs的红移和gamma射线谱指数较大,LBLs的红移和gamma射线谱指数都介于两者之间,它们之间可能存在一个从FSRQs经LBLs到HBLs的演化序列,HBLs与FSRQs有明显的不同,LBLs与FSRQs却很相似.

Thomas-Fermi方程的特征分析与数值求解

Thomas-Fermi方程在处理核——电近似模型中占有非常重要的地位,但就方程而言,方程是非线性的,精确求解非常困难。作者通过一个简单的实例导出方程,分析了方程的具体特征,提出了一种方程有效的数值求解方法。

Fermi Blazar天体同步辐射区域的能谱演化研究

收集了180个Fermi Blazar天体的射电波段、红外波段、光学波段、紫外波段和X射线波段的准同时性多波段观测数据,用二次函数拟合了同步辐射区域的能谱,根据能谱拟合得到的参数值,获得了同步辐射区域的峰值频率和多波段能谱指数.通过研究多波段谱指数与同步峰值频率的相关性,探讨了不同能谱类型的Blazar天体之间的演化规律.

Fermi型折射率分布平面光波导的模式

离子交换工艺制作的光波导在集成光学领域有着广泛的应用。研究表明,采用Ferm i函数可以很好地描述离子交换平面光波导折射率分布情况。对具有Ferm i折射率分布的离子交换平面光波导,采用A iry函数方法,求解了波动方程,给出了模方程和模场分布。利用所得到的模方程所进行的计算与已有的计算结果和测量值相比较,表明其精确度是比较好的。

已知红移Fermi/LAT暴的谱能关系

Fermi卫星的GBM可以更精确地测量Epeak,以及LAT在GeV能段的定位和观测,提供了一个独特的研究伽玛暴谱能关系之一Eiso-Epeak关系的机会.根据9个具有红移的Fermi/LAT暴的谱能关系,发现长暴的这个关系满足一定的关系,而短暴却不满足.

Jacobi场方程的解在Fermi坐标下的Taylor展开

给出了Jacobi场方程的解在Fermi坐标下的Taylor展开，推广了已有的结果。