arXiv subjects

Jiaxiang Wang

Publications and source records attributed to Jiaxiang Wang.

46 records · Page 3Linked to original sources

arXiv2014

Quantum phase transition in one-dimensional commensurate Frenkel-Kontorova model

In this paper, we have studied the one-dimensional commensurate quantum Frenkel-Kontorova model by a density-matrix renormalization group (DMRG) algorithm. The focus has been on its properties of the entanglement, the coordinate correlation, the ground state energy and the energy gap between the ground state and the first excited one. It is demonstrated that a quantum phase transition (QPT) between the pinned and the sliding phases takes place as the quantum fluctuation, measured by an effective Planck constant $\tilde\hbar$, increases to a threshold value $\tilde \hbar_c$.

cond-mat.stat-mech↗

arXiv2013

Influence of the intensity gradient upon HHG from free electrons scattered by an intense laser beam

When an electron is scattered by a tightly-focused laser beam in vacuum, the intensity gradient is a critical factor to influence the electron dynamics, for example, the electron energy exchange with the laser fields as have been explored before [P.X.Wang et al.,J. Appl. Phys. 91, 856 (2002]. In this paper, we have further investigated its influence upon the electron high-harmonic generation (HHG) by treating the spacial gradient of the laser intensity as a ponderomotive potential. Based upon perturbative QED calculations, it has been found that the main effect of the intensity gradient is the broadening of the originally line HHG spectra. A one-to-one relationship can be built between the beam width and the corresponding line width. Hence this finding may provides us a promising way to measure the beam width of intense lasers in experiments. In addition, for a laser pulse, we have also studied the different influences from transverse and longitudinal intensity gradients upon HHG.

physics.optics↗

arXiv2013

The interference effect of laser-assisted bremsstrahlung emission in Coulumb fields of two nuclei

In this paper, the spontaneous bremsstrahlung emission from an electron scattered by two fixed nuclei in an intense laser field is investigated in details based upon the Volkov state and the Dirac-Volkov propagator. It has been found that the fundamental harmonic spectrum from the electron radiation exhibits distinctive fringes, which is dependent not only upon the internucleus distance and orientation, but also upon the initial energy of the electron and the laser intensity. By analyzing the differential cross section, we are able to explain these effects in terms of interference among the electron scattering by the nuclei. These results could have promising applications in probing the atomic or molecular dressed potentials in intense laser fields.

physics.optics↗

arXiv2011

Dimensional Scaling Treatment with Relativistic Corrections for Stable Multiply Charged Atomic Ions in High-Frequency Super-Intense Laser Fields

We present a theoretical framework which describes multiply-charged atomic ions, their stability within super-intense laser fields,also lay corrections to the systems due to relativistic effects. Dimensional scaling calculations with relativistic corrections for systems: H, H$^{-}$, H$^{2-}$, He, He$^{-}$, He$^{2-}$, He$^{3-}$ within super-intense laser fields were completed. Also completed were three-dimensional self consistent field calculations to verify the dimensionally scaled quantities. With the aforementioned methods the system's ability to stably bind 'additional' electrons through the development of multiple isolated regions of high potential energy leading to nodes of high electron density is shown. These nodes are spaced far enough from each other to minimized the electronic repulsion of the electrons, while still providing adequate enough attraction so as to bind the excess elections into orbitals. We have found that even with relativistic considerations these species are stably bound within the field. It was also found that performing the dimensional scaling calculations for systems within the confines of laser fields to be a much simpler and more cost-effective method than the supporting D=3 SCF method. The dimensional scaling method is general and can be extended to include relativistic corrections to describe the stability of simple molecular systems in super-intense laser fields.

quant-ph↗

arXiv2008

A novel scheme for entanglement engineering in a fermionic system

We present a novel scheme to engineer the entanglement in a fermionic system, which is modeled by a minimally three-site Hubbard model. It is found that, in this type of system, we can have two free parameters. One is used to tune the entanglement and the other to switch on or off the above tuning function. The whole process is much like what happens in a traditional transistor switch, where the main current between the emitter and collector can be turned on or off by the base current.

quant-ph↗

arXiv2004

Combined effects of disorders and electron-electron interactions upon metal-insulator transition in 2D non-bipartite lattice

We examined the characteristics of a metal-insulator transition on a two-dimensional non-bipartite lattice when both disorders and electron interactions are present. Using a real-space renormalization group method and finite-size scaling analysis we have found that after the disordered system transits from the insulating state to the metal one, it can reenter an insulating state if there is a further increase in the electron-electron interactions.

cond-mat.str-el↗

arXiv2004

Finite-size scaling for Mott metal-insulator transition on a half-filled non-partite lattice

By applying a multi-stage real-space renormalization group procedure to Hubbard model, we examine the finite-size scaling in Mott metal-insulator transition(MIT) on a non-partite lattice. It is found that there exists a critic point U/t=12.5 for the MIT and the corresponding critical exponent for correlation length niu= 1 and the dynamic exponent z = 0.91 are obtained. On the critical point, the charge gap scales with the system size as Delta-g~1/L^0.91.

cond-mat.str-el↗

arXiv2004

Scaling of entanglement in finite arrays of exchange-coupled quantum dots

We present a finite-size scaling analysis of the entanglement in a two-dimensional arrays of quantum dots modeled by the Hubbard Hamiltonian on a triangular lattice. Using multistage block renormalization group approach, we have found that there is an abrupt jump of the entanglement when a first-order quantum phase transition occurs. At the critical point, the entanglement is constant, independent of the block size.

quant-ph↗

arXiv2004

Size effects in the electronic properties of finite arrays of exchange coupled quantum dots: A renormalization group approach

Transport properties of arrays of metallic quantum dots are governed by the distance-dependent exchange coupling between the dots. It is shown that the effective value of the exchange coupling, as measured by the charging energy per dot, depends monotonically on the size of the array. The effect saturates for hexagonal arrays of over 7^5 unit cells. The discussion uses a multi-stage block renormalization group approach applied to the Hubbard Hamiltonian. A first order phase transition occurs upon compression of the lattice and the size dependence is qualitatively different for the two phases.

quant-ph↗

arXiv2004

Scaling of entanglement at quantum phase transition for two-dimensional array of quantum dots

With Hubbard model, the entanglement scaling behavior in a two-dimensional itinerant system is investigated. It has been found that, on the two sides of the critical point denoting an inherent quantum phase transition (QPT), the entanglement follows different scalings with the size just as an order parameter does. This fact reveals the subtle role played by the entanglement in QPT as a fungible physical resource.

quant-ph↗