Heating, Cooling, and Equilibration of an Interacting Many-Fermion System

We discuss the process of equilibrium’s attainment in an interacting many-fermions system linked to a heat reservoir, whose temperature T is subject to a short-time disturbance of total duration 2τ. In this time-interval, its temperature increases up to a maximum value , cooling off afterward (also gradually) to its original value TM. The process is described by a typical master equation that leads eventually to equilibration. We discuss how the equilibration process depends upon 1) the system’s fermion-number, 2) the fermion-fermion interaction’s strength V, 3) the disturbance duration 2τ, and finally 4) the maximum number of equations N of the master equation.

High-pressure studies on heavy fermion systems

In this review article, we give a brief overview of heavy fermions, which are prototype examples of strongly correlated electron systems. We introduce the application of physical pressure in heavy fermion systems to construct their pressure phase diagrams and to study the close relationship between superconductivity（SC） and other electronic instabilities, such as antiferromagnetism（AFM）, ferromagnetism（FM）, and valence transitions. Field-angle dependent heat capacity and point-contact spectroscopic measurements under pressure are taken as examples to illustrate their ability to investigate novel physical properties of the emergent electronic states.

Electronic structure of heavy fermion system CePt_2In_7 from angle-resolved photoemission spectroscopy

We have carried out high-resolution angle-resolved photoemission measurements on the Ce-based heavy fermion compound CePt2In7that exhibits stronger two-dimensional character than the prototypical heavy fermion system CeCoIn5.Multiple Fermi surface sheets and a complex band structure are clearly resolved. We have also performed detailed band structure calculations on CePt2In7. The good agreement found between our measurements and the calculations suggests that the band renormalization effect is rather weak in CePt2In7. A comparison of the common features of the electronic structure of CePt2In7and CeCoIn5indicates that CeCoIn5shows a much stronger band renormalization effect than CePt2In7. These results provide new information for understanding the heavy fermion behaviors and unconventional superconductivity in Ce-based heavy fermion systems.

Exciton Model of Two-Fermion System

The two-componenl exciton model is applied for calculating the data ofnucleon induced reactions.The angular momentum and parity conservations are takeninto account.In terms of the calculated results of n+56Fe at En=14.5 MeV the physicalpicture of the two-component model has been analysed.

1-11 Angle Dependence of d-wave Pairing Gap in Two Component Fermion System

In a two component fermion system, the mismatched Fermi surfaces prevent the formation of Cooper pairsbetween the two spices near their average Fermi surface. Our previous work[1] has shown that the angle dependenceof the non s-wave pairing gap can reduce the effect of the difference μ between the Fermi surfaces of two spices inasymmetric nuclear matter. On the other hand, in the heavy fermion superconductors, such as CeCoIn5 pressuredCeRhIn5 NpPd5Al2 and Tl-based cuprates, may have a couple of common features, for example, the d-wave pairingand a strong paramagnetic effect (the difference of the two Fermi surfaces μ). Therefore, the angle dependence ofthe pairing gap may have significant influence in these systems.

Quantum phase transitions in two-dimensional strongly correlated fermion systems

In this article, we review our recent work on quantum phase transition in two-dimensional strongly correlated fermion systems. We discuss the metal insulator transition properties of these systems by calculating the density of states, double occupancy, and Fermi surface evolution using a com- bination of the cellular dynamical mean-field theory （CDMFT） and the continuous-time quantum Monte Carlo algorithm. Furthermore, we explore the magnetic properties of each state by defining magnetic order parameters. Rich phase diagrams with many intriguing quantum states, including antiferromagnetic metal, paramagnetic metal, Kondo metal, and ferromagnetic insulator, were found for the two-dimensional lattices with strongly correlated fermions. We believe that our results would lead to a better understanding of the properties of real materials.

对高维Schwarzschild-de Sitter黑洞视界处Fermions量子隧穿辐射率的修正

根据Lorentz-breaking理论对弦量场作用量进行修正并应用变分原理得到了高维Schwarzschild-de Sitter黑洞时空中的费米子动力学方程。通过对此动力学方程的研究得到了高维Schwarzschild-de Sitter黑洞事件视界处和宇宙视界处的量子隧穿率的修正形式,从而研究了此黑洞事件视界处和宇宙视界处的修正形式的Hawking温度和Bekenstein-Hawking熵的新的表达式。在得到研究结果的基础之上,文中最后还对研究方法和结论进行了讨论。

Approximate Private Quantum Channels on Fermionic Gaussian Systems

The private quantum channel (PQC) maps any quantum state to the maximally mixed state for the discrete as well as the bosonic Gaussian quantum systems, and it has fundamental meaning on the quantum cryptographic tasks and the quantum channel capacity problems. In this paper, we primally introduce a notion of approximate private quantum channel (ε-PQC) on fermionic Gaussian systems (i.e., ε-FPQC), and construct its explicit form of the fermionic (Gaussian) private quantum channel. First of all, we suggest a general structure for ε-FPQC on the fermionic Gaussian systems with respect to the Schatten p-norm class, and then we give an explicit proof of the statement in the trace norm case. In addition, we study that the cardinality of a set of fermionic unitary operators agrees on the ε-FPQC condition in the trace norm case. This result may give birth to intuition on the construction of emerging fermionic Gaussian quantum communication or computing systems.

Entanglement Evolution of a 2-Qutrit System Interacting with a Fermionic Bath

Based on the algebraic entanglement measure proposed [G. Vidal et al., Phys. Rev. A 65 (2002) 032314],we study the entanglement evolution of both pure quantum states and mixed ones of 2-qutrit system in a symmetrybroken environment consisting of a fermionic bath. Entanglement of states will decrease or remain constant under the influence of environment, and the class of states which remain unchanged has been found out.

Thermodynamic stability of interacting fermions system with matrix eigenvalue method

A matrix eigenvalue method is applied to analyse the thermodynamic stability of two-component interacting fermions. The non-relativistic and ultra-relativistic d = 1, 2, 3 dimensions have been discussed in detail, respectively. The corresponding stability region has been given according to the two-body interaction strength and the particle number density ratio.

Chiral magnetic effect for chiral fermion system

The chiral magnetic effect is concisely derived by employing the Wigner function approach in the chiral fermion system.Subsequently,the chiral magnetic effect is derived by solving the Landau levels of chiral fermions in detail.The second quantization and ensemble average leads to the equation of the chiral magnetic effect for righthand and lefthand fermion systems.The chiral magnetic effect arises uniquely from the contribution of the lowest Landau level.We carefully analyze the lowest Landau level and find that all righthand(chirality is+1)fermions move along the direction of the magnetic field,whereas all lefthand(chirality is-1)fermions move in the opposite direction of the magnetic field.Hence,the chiral magnetic effect can be explained clearly using a microscopic approach.

Majorana fermion realization and relevant transport processes in a triple-quantum dot system

Nonequilibrium electronic transports through a system hosting three quantum dots hybridized with superconductors are investigated. By tuning the relative positions of the dot levels, we illustrate the existence of Majorana fermions and show that the Majorana feimions will either survive separately on single dots or distribute themselves among different dots with tunable probabilities. As a result, different physical mechanisms appear, including local Andreev reflection（LAR）,cross Andreev reflection（CAR）, and cross resonant tunneling（CRT）. The resulting characteristics may be used to reveal the unique properties of Majorana fermions. In addition, we discuss the spin-polarized transports and find a pure spin current and a spin filter effect due to the joint effect of CRT and CAR, which is important for designing spintronic devices.

Controlling Fusion of Majorana Fermions in One-Dimensional Systems by Zeeman Field

We propose the realization of Majorana fermions （MFs） on the edges of a two-dimensional topological insulator in the proximity with s-wave superconductors and in the presence of transverse exchange field h. It is shown that there appear a pair of MFs localized at two junctions and that a reverse in the direction of h can lead to permutation of two MFs. With decreasing h, the MF states can either be fused or form one Dirac fermion on the π-junctions, exhibiting a topological phase transition. This characteristic can be used to detect physical states of MFs when they are transformed into Dirac fermions MFs is also given. localized on the π-junction. A condition of decoupling two

On the Quantum Statistical Distributions Describing Finite Fermions and Bosons Systems

A century old methodology for deriving statistical distribution using approximate Stirling’s formulation of the factorial becomes questionable. By avoiding the use of exaggerated approximations, a new picture of the energy distribution of fermions and bosons are presented. Energy distribution among fermions (or bosons) in systems with finite degeneracy are found to be degeneracy dependent. The presented point of view explains, successfully, presence of degeneracy pressure in ultra-cooled Fermi gas and predicts the minimum accessible temperature for finite degeneracy fermions system.

Bound States of a System of Two Fermions on Invariant Subspace

We consider a Hamiltonian of a system of two fermions on a three-dimensional lattice Z3 with special potential . The corresponding Shrödinger operator H(k) of the system has an invariant subspac L-123(T3) , where we study the eigenvalues and eigenfunctions of its restriction H-123(k). Moreover, there are shown that H-123(k1, k2, π) has also infinitely many invariant subspaces , where the eigenvalues and eigenfunctions of eigenvalue problem are explicitly found.

Magnetism, heat capacity, magnetocaloric effect, and magneto-transport properties of heavy fermion antiferromagnet CeGaSi

We synthesize high-quality single crystal of CeGaSi by a Ga self-flux method and investigate its physical properties through magnetic susceptibility,specific heat and electrical resistivity measurements as well as high pressure effect.Magnetic measurements reveal that an antiferromagnetic order develops below T_(m)~10.4 K with magnetic moments orientated in the ab plane.The enhanced electronic specific heat coefficient and the negative logarithmic slope in the resistivity of CeGaSi indicate that the title compound belongs to the family of Kondo system with heavy fermion ground states.The max magnetic entropy change-ΔS_(M)^(max)(μ_(0)H⊥c,μ_(0)H=7 T) around T_(m) is found to reach up to 11.85 J·kg^(-1)·K^(-1).Remarkably,both the antiferromagnetic transition temperature and-ln T behavior increase monotonically with pressure applied to 20 kbar(1 bar=10~5 Pa),indicating that much higher pressure will be needed to reach its quantum critical point.

Charm physics with overlap fermions on 2+1-flavor domain wall fermion configurations

Decay constants of pseudoscalar mesons D,D_(s),η_(c) and vector mesons D^(*),D_(s)^(*),J/ψ are determined from the N_(f)=2+1 lattice QCD at a lattice spacing a~0.08 fm.For vector mesons,the decay constants defined by tensor currents are given in the MS scheme at 2 GeV.The calculation is performed on domain wall fermion configurations generated by the RBC-UKQCD collaborations and the overlap fermion action is used for the valence quarks.Comparing the current results with our previous results at a coarser lattice spacing a ~0.11 fm provides a better understanding of the discretization error.We obtain f_(D_(s)^(*))^(T)(MS,2 GeV)/f_(D_(s)^(*))=0.909(18)with a better precision than our previous result.Combining our f_(D_(s)^(*))=277(11)MeV with the total width of D_(s)^(*) determined in a recent study gives a branching fraction 4.26(52)×10^(-5) for D_(s)^(*) leptonic decay.

Comprehensive constraints on fermionic dark matter-quark tensor interactions in direct detection experiments

Effective field theory(EFT)provides a model-independent framework for interpreting the results of dark matter(DM)direct detection experiments.In this study,we demonstrate that the two fermionic DM-quark tensor operators(χiσ^(μν)γ^(5)χ)(qσ_(μν)q)and(χσ_(μν)χ)(qσ_(μν)q)can contribute to the DM electric and magnetic dipole moments via nonperturbative QCD effects,in addition to the well-studied contact DM-nucleon operators.We then investigate the constraints on these two operators by considering both the contact and dipole contributions using the XENON1T nuclear recoil and Migdal effect data.We also recast other existing bounds on the DM dipole operators,derived from electron and nuclear recoil measurements in various direct detection experiments,as constraints on the two tensor operators.For m_(χ)■1GeV,our results significantly extend the reach of constraints on the DM-quark tensor operators to masses as low as 5MeV,with the bound exceeding that obtained by the Migdal effect with only contact interactions by approximately an order of magnitude.In particular,for the operator(χσ^(μν)iγ5χ)(qσ_(μν)q)with DM mass m_(χ)■10GeV,the latest PandaX constraint on the DM electric dipole moment puts more stringent bounds than the previous direct detection limit.We also briefly discuss the constraints obtained from experiments other than direct detection.

Elementary Fermions: Strings, Planck Constant, Preons and Hypergluons

Using real fields instead of complex ones, it is suggested here that the fermions are pairs of coupled strings with an internal tension. The interaction between the two coupled strings is due to an exchange mechanism which is proportional to Planck’s constant. This may be the result of two massless bosons (hypergluons) coupled by a preon (prequark) exchange. It also gives a physical explanation to the origin of the Planck constant, and origin of spin.

Fermions: Spin, Hidden Variables, Violation of Bell’s Inequality and Quantum Entanglement

Using real fields instead of complex ones, it was recently claimed, that all fermions are made of pairs of coupled fields (strings) with an internal tension related to mutual attraction forces, related to Planck’s constant. Quantum mechanics is described with real fields and real operators. Schrodinger and Dirac equations then are solved. The solution to Dirac equation gives four, real, 2-vectors solutions ψ1=(U1D1)ψ2=(U2D2)ψ3=(U3D3)ψ4=(U4D4)where (ψ1,ψ4) are coupled via linear combinations to yield spin-up and spin-down fermions. Likewise, (ψ2,ψ3) are coupled via linear combinations to represent spin-up and spin-down anti-fermions. For an incoming entangled pair of fermions, the combined solution is Ψin=c1ψ1+c4ψ4where c1and c4are some hidden variables. By applying a magnetic field in +Z and +x the theoretical results of a triple Stern-Gerlach experiment are predicted correctly. Then, by repeating Bell’s and Mermin Gedanken experiment with three magnetic filters σθ, at three different inclination angles θ, the violation of Bell’s inequality is proven. It is shown that all fermions are in a mixed state of spins and the ratio between spin-up to spin-down depends on the hidden variables.