共查询到20条相似文献,搜索用时 31 毫秒
1.
The study of entanglement properties of quantum critical many-particle systems has become a subject of intense interest. While
the basic features of entanglement scaling for critical spin-1/2 systems (coupled qubits) are by now fairly well understood,
entanglement properties of critical fermions (or bosons) are less well studied. In an effort to contribute to this problem,
we have analyzed the single-site entanglement of a generic spin-1/2 lattice fermion system and found that (under certain provisos)
this measure can be used as a reliable marker to identify and partly characterize a quantum critical point. We illustrate
our findings by exact analytical results for the single-site entanglement at the magnetic and Mott-Hubbard transitions of
the 1D Hubbard model and at the Mott-Hubbard transitions of the 1D Hubbard model with long-range hopping.
The text was submitted by the authors in English. 相似文献
2.
An exact solution of a single impurity model is hard to derive since it breaks translation invariance symmetry. We present the exact solution of the spin-1/2 transverse Ising chain imbedded by a spin-1 impurity. Using the hole decomposition scheme, we exactly solve the spin-1 impurity in two subspaces which are generated by a conserved hole operator.The impurity enlarges the energy deformation of the ground state above a pure transverse Ising system without impurity.The specific heat coefficient shows a small anomaly at low temperature for finite size. This indicates that the impurity can tune the ground state from a magnetic impurity space to a non-magnetic impurity space, which only exists for spin-1impurity comparing with spin-1/2 impurity and a pure transverse Ising chain without impurity. These behaviors essentially come from adding impurity freedom, which induces a competition between hole and fermion excitation depending on the coupling strength with its neighbor and the single-ion anisotropy. 相似文献
3.
Xi-Wen Guan 《Frontiers of Physics》2012,7(1):8-15
Using solutions of the discrete Bethe ansatz equations, we study in detail the quantum impurity problem of a spin-down fermion immersed into a fully ploarized spin-up Fermi sea with weak attraction. We prove that this impurity fermion in the one-dimensional (1D) fermionic medium behaves like a polaron for weak attraction. However, as the attraction grows, the spin-down fermion binds with one spin-up fermion from the fully-polarized medium to form a tightly bound molecule. Thus it is seen that the system undergos a crossover from a mean field polaron-like nature into a mixture of excess fermions and a bosonic molecule as the attraction changes from weak attraction into strong attraction. This polaron-molecule crossover is universal in 1D many-body systems of interacting fermions. In a thermodynamic limit, we further study the relationship between the Fredholm equations for the 1D spin-1/2 Fermi gas with weakly repulsive and attractive delta-function interactions. 相似文献
4.
Paul H. Frampton 《Physics letters. [Part B]》1984,140(5-6):313-316
In a general even space-time dimension I consider spin-1/2 fermions coupled to SU(N) Yang-Mills fields and to gravity. It is shown (unexpectedly) that, once the chiral gauge anomaly is cancelled, gravitational anomalies do not further constrain the fermion representation. 相似文献
5.
《中国科学:物理学 力学 天文学(英文版)》2017,(12)
Ever since the pioneering work of Bardeen, Cooper and Schrieffer in the 1950 s, exploring novel pairing mechanisms for fermion superfluids has become one of the central tasks in modern physics. Here, we investigate a new type of fermion superfluid with hybridized s-and p-wave pairings in an ultracold spin-1/2 Fermi gas. Its occurrence is facilitated by the co-existence of comparable s-and p-wave interactions, which is realizable in a two-component 40 K Fermi gas with close-by s-and p-wave Feshbach resonances. The hybridized superfluid state is stable over a considerable parameter region on the phase diagram, and can lead to intriguing patterns of spin densities and pairing fields in momentum space. In particular, it can induce a phase-locked p-wave pairing in the fermion species that has no p-wave interactions. The hybridized nature of this novel superfluid can also be confirmed by measuring the s-and p-wave contacts, which can be extracted from the high-momentum tail of the momentum distribution of each spin component. These results enrich our knowledge of pairing superfluidity in Fermi systems, and open the avenue for achieving novel fermion superfluids with multiple partial-wave scatterings in cold atomic gases. 相似文献
6.
The spin-3/2 fermion models with contact interactions have a generic SO5 symmetry without any fine-tuning of parameters. Its physical consequences are discussed in both the continuum and lattice models. A Monte Carlo algorithm free of the sign problem at any doping and lattice topology is designed when the singlet and quintet interactions satisfy U0< or = U2< or = -3/5 U0 (U0< or = 0), thus making it possible to study different competing orders with high numerical accuracy. This model can be accurately realized in ultracold atomic systems. 相似文献
7.
Pierre Fayet 《Physics letters. [Part B]》1979,84(4):416-420
The mass2 splittings between leptons and quarks and their spin-0 partners under supersymmetry are related to the goldstino couplings. The bosonic partner of the goldstino cannot be the photon itself. But it should be, in part, a linear combination of the various neutral gauge bosons. As a result, mass relations constrain the neutral current structure of the theory. They require the existence of at least two neutral gauge bosons in addition to the photon and suggest the possibility of a universal mass2 splitting between leptons and quarks and their spin-0 partners. 相似文献
8.
9.
G. B. Mainland 《Few-Body Systems》2006,39(1-2):101-122
A complete set of numerical solutions is obtained, in the ladder approximation, to the Bethe-Salpeter equation describing
bound states of a spin-
fermion and spin-0 boson with arbitrary masses that interact via the exchange of a massive, spin-0 boson. The equation has
been used previously, without solutions actually being calculated, to derive some properties of nucleons by treating the physical
nucleon as a bound state of a “bare” nucleon and a “bare” meson. It is likely that most, if not all, two-body, bound-state
Bethe-Salpeter equations can be solved in the ladder approximation using the method discussed here. 相似文献
10.
Fermions tunneling from rotating stationary Kerr black hole with electric charge and magnetic charge
In this paper, the method of semi-classical fermion tunneling is extended to explore the fermion tunneling behavior of a Kerr–Newman–Kasuya black hole. Thus, the Hamilton–Jacobi equation in Kerr–Newman–Kasuya space–time is derived by the method presented in Refs. Lin and Yang (2009) [24], [25], [26], the Hawking temperature at the horizon and the tunneling probability of spin- 1/2 fermions are finally obtained following the semi-classical quantum equation. The results indicate the common features of this black hole. 相似文献
11.
12.
The mixed spin-1/2 and spin-1 Ising chain with both longitude and transverse single-ion anisotropies Dz and Dx is solved exactly by means of a mapping to the spin-1/2 Ising chain with the alternating transverse fields and the Jordan-Wigner transformation. The analytical expressions of the quasi-particles' spectra Λk, the minimal energy gap Δ0 for exciting a fermion quasi-particle, the minimal energy gap Δh for exciting a hole, and the ground state energy are obtained. The phase diagram of the ground state is also given. The results show that when Dz?0 for any finite value of Dx, there is no quantum critical point and the ground state is always in a spin ordered phase disregard of the boundary condition in the present system. 相似文献
13.
Using the Majorana fermion representation of spin-1/2 local moments, we show how the dynamic spin correlation and susceptibility are obtained directly from the one-particle Majorana propagator. We illustrate our method by applying it to the spin dynamics of a nonequilibrium quantum dot, computing the voltage-dependent spin relaxation rate and showing that, at weak coupling, the fluctuation-dissipation relation for the spin of a quantum dot is voltage dependent. We confirm the voltage-dependent Curie susceptibility recently found by Parcollet and Hooley [Phys. Rev. B 66, 085315 (2002)]]. 相似文献
14.
We show that multiple layered Dirac cones can emerge in the band structure of properly addressed multicomponent cold fermionic gases in optical lattices. The layered Dirac cones contain multiple copies of massless spin-1/2 Dirac fermions at the same location in momentum space, whose different Fermi velocity can be tuned at will. On-site microwave Raman transitions can further be used to mix the different Dirac species, resulting in either splitting of or preserving the Dirac point (depending on the symmetry of the on-site term). The tunability of the multiple layered Dirac cones allows us to simulate a number of fundamental phenomena in modern physics, such as neutrino oscillations and exotic particle dispersions with E~p(N) for arbitrary integer N. 相似文献
15.
16.
José F. Nieves Palash B. Pal 《The European Physical Journal C - Particles and Fields》2009,63(2):331-342
Various processes that are forbidden in vacuum due to angular momentum conservation can occur in a medium that is isotropic
and does not carry any angular momentum. We illustrate this by considering explicitly two examples. The first one is the decay
of a spin-0 particle into a photon and another spin-0 particle, using a model involving the Yukawa interactions of the scalar
particles with a charged fermion field. The second one involves the decay of a neutrino into another neutrino and a graviton,
in the standard model of particle interactions augmented with the linearized gravitational couplings. 相似文献
17.
18.
We study the linear anisotropic spin-1/2-Heisenberg model with periodic as well as antiperiodic boundary conditions. Using two assumptions about the eigenvalues of the related fermion models it is shown, how the exactly known energy spectrum of the periodic Heisenberg model is altered in the antiperiodic case. This investigation provides basis for a subsequent test of a Hartree-Fock approximation. It gives fairly good results for the groundstate energy and the energy dispersion of low-lying excitations. Hartree-Fock solutions with gapless excitations yield a qualitatively correct picture of the phase diagram of the Heisenberg model. 相似文献
19.
M. Alimohammadi A. Shariati 《The European Physical Journal C - Particles and Fields》2001,21(1):193-196
Berry phase for a spin-1/2 particle moving in a flat space-time with torsion is investigated in the context of the Einstein–Cartan–Dirac
model. It is shown that if the torsion is due to a dense polarized background, then there is a Berry phase only if the fermion
is massless and its momentum is perpendicular to the direction of the background polarization. The order of magnitude of this
Berry phase is discussed in other theoretical frameworks.
Received: 12 February 2001 / Revised version: 2 May 2001 / Published online: 29 June 2001 相似文献
20.
We propose a two-stage spin-quenching scenario for the unusual heavy fermion state realized in the mixed valent metal LiV2O4. In this theory, local valence fluctuations are responsible for the formation of partially quenched, spin-1 / 2 moments below room temperature. Frustration of the intersite spin couplings then drives the system to produce the heavy Fermi liquid seen at low temperatures. The anomalous resistivity and the sign change of the Hall constant can be understood naturally within this model, which also predicts a unique symmetry for the heavy quasiparticle bands that may be observed in de Haas-van Alphen experiments. 相似文献