Quantum phase transitions in matrix product states of one-dimensional spin-1 chains

We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equM coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement.     

Effects of the Next Nearest Neighbor Hopping on Superconductivity and Antiferromagnetism of Gossamer Superconductivity

The two dimensions hole-doped t-t '-J-U model was studied based on the Gutzwiller approach and the renormalized mean-field theory.The phase diagrams of gossamer superconductors and the effects of the next-nearestneighbor hopping(t ') on superconductivity and antiferromagnetism based on the t-t '-J-U model were investigated.The results show that the qualitative feature of the phase diagrams in the t-t '-J-U model is the same as in the case of the t-J-U model.The antiferromagnetic order coexists with the d-wave superconductivity(dSC) in the underdoped region below the doping δ≈ 0.1 and is enhanced by the t '.The dSC order is slightly suppressed by t ' in the underdoped region and greatly enhanced in the overdoped region.The dSC order is pushed to a larger doping region and the coexistence region of the AF and dSC extends to higher doping.     

Quantum phase transitions in matrix product states of one-dimensional spin-1 chains

We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equal coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement.     

Coexistence of Two Mechanisms for Extracting Energy from a Rotating Black Hole

Evolution characteristics of a rotating black hole (BH) are discussed in coexistence of the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process in the parameter space consisting of the BH spin and the power-law index of the magnetic field on the disc. The condition for the coexistence of the two energy mechanisms are derived by using the mapping relation between the angular coordinate on the BH horizon and the radial coordinate on the disc. It is shown that not only the two mechanisms can coexist, but also the power and the rate of change of BH entropy in the BZ process will dominate over those in the MC process, provided that the BH spin and the power-law index are great enough.     

Superconductivity,Pair Density Wave,and Néel Order in Cuprates

We investigate in underdoped cuprates possible coexistence of the superconducting order at zero momentum and pair density wave(PDW) at momentum Q=(π,π) in the presence of a Neel order.By symmetry,the d-wave uniform singlet pairing dS₀ can coexist with the d-wave triplet PDW dT_Q,and the p-wave singlet PDW pS_Q can coexist with the p-wave uniform triplet pT₀.At half filling,we find that the novel pS_Q+pT₀ state is energeticall.y more ...     

Reverse Monte Carlo study on structural order in liquid and glassy AlFe alloys

This paper reports that anomalous local order in liquid and glassy AlFeCe alloy has been detected by x-ray diffraction measurements. The addition of the element Ce has a great effect on this local structural order. The element Ce favours interpenetration of the icosahedra by sharing a common face and edges. It argues that frustration between this short-range order and the long-range crystalline order controls the glass-forming ability of these liquids. The obtained results suggest that a system having a stronger tendency to show local icosahedral order should be a better glass-former. This scenario also naturally explains the close relationship between the local icosahedral order in a liquid, glass-forming ability, and the nucleation barrier. Such topological local order has also been analysed directly using the reverse Monte Carlo method. It also estimated the fraction of local ordered and disordered structural units in a glassy AlFeCe alloy.     

First-order character of the displacive structural transition in BaWO₄

Nearly all displacive transitions have been considered to be continuous or second order,and the rigid unit mode(RUM) provides a natural candidate for the soft mode.However,in-situ X-ray diffraction and Raman measurements show clearly the first-order evidences for the scheelite-to-fergusonite displacive transition in BaWO 4:a 1.6% volume collapse,coexistence of phases,and hysteresis on release of pressure.Such first-order signatures are found to be the same as the soft modes in BaWO 4,which indicates the scheelite-to-fergusonite displacive phase transition hides a deeper physical mechanism.By the refinement of atomic displacement parameters,we further show that the first-order character of this phase transition stems from a coupling of large compression of soft BaO 8 polyhedrons to the small displacive distortion of rigid WO 4 tetrahedrons.Such a coupling will lead to a deeper physical insight in the phase transition of the common scheelite-structured compounds.     

First-order character of the displacive structural transition in BaWO4

Nearly all displacive transitions have been considered to be continuous or second order, and the rigid unit mode （RUM） provides a natural candidate for the soft mode. However, in-situ X-ray diffraction and Raman measurements show clearly the first-order evidences for the scheelite-to-fergusonite displacive transition in SaWO4： a 1.6% volume collapse, coexistence of phases, and hysteresis on release of pressure. Such first-order signatures are found to be the same as the soft modes in BaWO4, which indicates the scheelite-to-fergusonite displacive phase transition hides a deeper physical mechanism. By the refinement of atomic displacement parameters, we further show that the first-order character of this phase transition stems from a coupling of large compression of soft BaOs polyhedrons to the small displacive distortion of rigid WO4 tetrahedrons. Such a coupling will lead to a deeper physical insight in the phase transition of the common scheelite-structured compounds.     

Coexistence and Extinction Pattern of Asymmetric Cyclic Game Species in a Square Lattice

The co-evolutionary dynamics of a cyclic game system is investigated in a two-dimensional square lattice with the asymmetrical rates for three species. Different with the well-mixed system, coexistence and extinction emerge alternately in the system, where a ＂zero-one＂ behavior is robust for a small population size, whereas, the system is predominated by coexistence for a big population one. We study in detail the influence about the fluctuation to the change of the state, and find that the difference between the maximal amplitude about the fluctuation and the average intensity determines which state the system is ultimately. In addition, we introduce Ports energy to explain the reason of the ＂zero-one＂ behavior. It is shown that the average Ports energy per site is the distance to the ＂zero-one＂ behavior in the model.     

Critical Analyses of Order Parameter and Phase Transitions at High Density in Gross－Neveu Model

By critical analyses of the order parameter of symmetry breaking, we have researched the phase transitions at high density in D = 2 and D = 3 Gross-Neveu (GN) model and shown that the gap equation obeyed by the dynamical fermion mass has the same effectivenesss as the effective potentials for such analyses of all the second order and some specJal first order phase transitions. In the meantime we also further ironed out a theoretical divergence and proven that in D = 3 GN model a first order phase transition does occur in the case of zero temperature and finite chemical potential.     

Guided modes in asymmetric metal-cladding left-handed material waveguides

We investigate guided modes in the asymmetric waveguide structure with a left-handed material (LHM) layer surrounded by air and metal. A graphical method is proposed to determine the guided modes. New properties of the oscillating and surface guided modes, such as absence of the fundamental mode, coexistence of the oscillating and surface guided modes, fast attenuation of the surface guided modes, and mode degeneracy, are analyzed in detail. We also investigate dispersive characteristics of the metal-LHM- air optical waveguide. The propagation constant increases with decreasing slab thickness for the first-order oscillating mode, which is different from that in traditional metal-cladding waveguides.     

Physics picture from neutron scattering study on Fe-based superconductors

Neutron scattering, with its ability to measure the crystal structure, the magnetic order, and the structural and magnetic excitations, plays an active role in investigating various families of Fe-based high-T c superconductors. Three different types of antiferromagnetic orders have been discovered in the Fe plane, but two of them cannot be explained by the spin-density-wave (SDW) mechanism of nesting Fermi surfaces. Noticing the close relation between antiferromagnetic order and lattice distortion in orbital ordering from previous studies on manganites and other oxides, we have advocated orbital ordering as the underlying common mechanism for the structural and antiferromagnetic transitions in the 1111, 122, and 11 parent compounds. We observe the coexistence of antiferromagnetic order and superconductivity in the (Ba,K)Fe 2 As 2 system, when its phase separation is generally accepted. Optimal T c is proposed to be controlled by the local FeAs 4 tetrahedron from our investigation on the 1111 materials. The Bloch phase coherence of the Fermi liquid is found crucial to the occurrence of bulk superconductivity in iron chalcogenides of both the 11 and the 245 families. Iron chalcogenides carry a larger staggered magnetic moment ( 2 μ B /Fe) than that in iron pnictides ( 1 μ B /Fe) in the antiferromagnetic order. Normal state magnetic excitations in the 11 superconductor are of the itinerant nature while in the 245 superconductor the spin-waves of localized moments. The observation of superconducting resonance peak provides a crucial piece of information in current deliberation of the pairing symmetry in Fe-based superconductors.     

Characteristics of titanium oxide memristor with coexistence of dopant drift and a tunnel barrier

The recent published experimental data of titanium oxide memristor devices which are tested under the same experi- mental conditions exhibit the strange instability and complexity of these devices. Such undesired characteristics preclude the understanding of the device conductive processes and the memristor-based practical applications. The possibility of the coexistence of dopant drift and tunnel barrier conduction in a memristor provides preliminary explanations for the undesired characteristics. However, current research lacks detailed discussion about the coexistence case. In this paper, dopant drift and tunnel barrier-based theories are first analyzed for studying the relations between parameters and physical variables which affect characteristics of mernristors, and then the influences of each parameter change on the conductive behaviors in the single and coexistence cases of the two mechanisms are simulated and discussed respectively. The simulation results provide further explanations of the complex device conduction. Theoretical methods of eliminating or reducing the coex- istence of the two mechanisms are proposed, in order to increase the stability of the device conduction. This work also provides the support for optimizing the fabrications of memristor devices with excellent performance.     

Spin-exchange relaxation of naturally abundant Rb in a K-Rb-~(21)Ne self-compensated atomic comagnetometer

The total effective spin-exchange relaxation of naturally abundant Rb in a K–Rb–21Ne comagnetometer is analyzed,and the results show that the coexistence of 87Rb and 85Rb isotopes in the same volume can lead to a large extra spinexchange broadening compared to pure 87Rb.This broadening mainly comes from the contribution of the equivalent reduction in the Rb spin-exchange rate.On this basis,an approximate relaxation model is proposed and experimentally demonstrated to be more accurate than that from a previous work.This study also provides a method for determining the properties of alkali-metal vapor cells.     

An experiment of dynamical behaviours in an erbium-doped fibre-ring laser with loss modulation

This paper reports a systematic experimental investigation on the dynamics in the low-frequency region in an erbium-doped fibre-ring laser with loss modulation. A rich variety of bifurcation is analyzed through the bifurcation diagram and structured with the concept of the winding numbers. The coexistence of multiple attractors and the crisis that appear in the saddle-node bifurcations, and an interesting structure of bifurcation which is similar to the bifurcations in high-frequency range, have been observed.     

Tri-hexagonal charge order in kagome metal CsV3Sb5 revealed by 121Sb nuclear quadrupole resonance

We report ¹²¹Sb nuclear quadrupole resonance(NQR)measurements on kagome superconductor CsV₃Sb₅ with Tc=2.5 K.¹²¹Sb NQR spectra split after a charge density wave(CDW)transition at 94 K,which demonstrates a commensurate CDW state.The coexistence of the high temperature phase and the CDW phase between 91 K and 94 K manifests that it is a first order phase transition.The CDW order exhibits tri-hexagonal deformation with a lateral shift between the adjacent kagome layers,which is consistent with 2×2×2 superlattice modulation.The superconducting state coexists with CDW order and shows a conventional s-wave behavior in the bulk state.     

Topological aspects in a two-component Bose condensed system in neutron star

By making use of Duan--Ge's decomposition theory of gauge potential and the topological current theory proposed by Prof. Duan Yi-Shi, we study a two-component superfluid Bose condensed system, which is supposed to be realized in the interior of neutron stars in the form of the coexistence of a neutron superfluid and a protonic superconductor. We propose that this system possesses vortex lines. The topological charges of the vortex lines are characterized by the Hopf indices and the Brower degrees of φ-mapping.     

Superconductivity,Pair Density Wave,and Neel Order in Cuprates

We investigate in underdoped cuprates possible coexistence of the superconducting order at zero momentum and pair density wave(PDW)at momentum Q=(Л,Л)in the presence of a Neel order.By symmetry,the d-wave uniform singlet pairing dS0 can coexist with the d-wave triplet PDW dTq,and the p-wave singlet PDW pSq can coexist with the p-wave uniform triplet pT0.At half filling,we find that the novel pSq+pT0 state is energetically more favorable than the dS0+dTQ state.At finite doping,however,the dS0+dTq state is more favorable.In both types of states,the variational triplet parameters cITq and pT0 are of secondary significance.Our results point to a fully symmetric Z2 quantum spin liquid with spinon Fermi surface in proximity to the Neel order at zero doping,which may not be adiabatically connected to the d-wave singlet superconductivity at finite doping with intertwining d-wave triplet PDW fluctuations and spin moment fluctuations.The results are obtained by variational quantum Monte Carlo simulations.     

Switching Behavior Induced by Electric and Magnetic Fields in （La0.73Bi0.27）0.67Ca0.33MnO3

Both electric and magnetic field-induced switching behaviors between a high resistive state and a low resistive one are observed in （La0.73Bi0.27）0.67Ca0.33MnO3. The effects of magnetoresistance a.nd electric-resistance suggest that the applied electric field and magnetic field greatly tune the percolative paths in the phase-separated system. According to the experimental results, the switching behaviors may come from the coexistence of the charge ordering state, and localized and freedom ferromagnetic states, in which the external field destroys partially the localized ferromagnetic states and charge ordering leads to the ferromagnetic state growth, which causes a switch between a high resistive state and low resistive one. This makes the doped manganite a good system for both electric and magnetic field sensor materials.     

Simultaneous study of the lower order harmonic and photoelectron emission from an atom in intense laser pulse

We simultaneously investigate variations of a low order harmonic and photoelectron emission with an incident laser intensity by solving the time-dependent Schr o¨dinger equation in a momentum space. It can be found that, the intensity of low order harmonic and photoelectron are gradually enhanced with the increase of the laser intensity, when the laser frequency is not in resonance with the transition frequency between the laser-induced high excited states and the ground state. If the resonance occurs, the intensity of the lower order harmonic is reduced and the interference can be observed in the lower order photoelectron spectra.