arXiv subjects

Ji Luo

Publications and source records attributed to Ji Luo.

27 records · Page 2Linked to original sources

arXiv2013

One-dimensional electronic solitons of graphene in an electromagnetic field

Electronic energy-eigen-states of graphene in an orthogonal electromagnetic field with relative magnitude beta=E/vf*B>=1 or in a pure electric field are obtained by a differential-equation method. Gaussian wave packets of probability density are constructed and found to transform form two-dimensional solitons into one-dimension ones at beta=1, when beta increases form beta<1 into beta>1. The maximum number of one-dimensional solitons of a finite graphene in the field is used to determine the electronic energy levels. These energy levels and the velocity of solitons lead to nonlinear dependence of the current on the Hall voltage for the field with beta>1 and nonlinear current-voltage curves for the pure electric field including the step-like ones at low temperatures, according to the ballistic transport of solitons.

cond-mat.mes-hall↗

arXiv2012

Role of electrical field in quantum Hall effect of graphene

The ballistic motion of carriers of graphene in an orthogonal electromagnetic field is investigated to explain Hall conductance of graphene under experimental conditions. With the electrical field, all electronic eigen-states have the same expectation value of the velocity operator, or classically, all carriers move in cycloids with the same average velocity. The magnitude of this velocity is just appropriate to generate the quantized Hall conductance which is in turn exactly independent of the external field. Electrical field changes each Landau level into a bundle of energies, whose overlap in large fields destroys the quantized Hall conductance. As the electrical field tends to the critical point, Landau level expansion occurs. As a result, saturation of the Hall conductance may be observed.

cond-mat.mes-hall↗

arXiv2011

Annular wave packets at Dirac points and probability oscillation in graphene

Wave packets in graphene whose central wave vector is at Dirac points are investigated by numerical calculations. Starting from an initial Gaussian function, these wave packets form into annular peaks that propagate to all directions like ripple-rings on water surface. At the beginning, electronic probability alternates between the central peak and the ripple-rings and transient oscillation occurs at the center. As time increases, the ripple-rings propagate at the fixed Fermi speed, and their widths remain unchanged. The axial symmetry of the energy dispersion leads to the circular symmetry of the wave packets. The fixed speed and widths, however, are attributed to the linearity of the energy dispersion. Interference between states that respectively belong to two branches of the energy dispersion leads to multiple ripple-rings and the probability-density oscillation. In a magnetic field, annular wave packets become confined and no longer propagate to infinity. If the initial Gaussian width differs greatly from the magnetic length, expanding and shrinking ripple-rings form and disappear alternatively in a limited spread, and the wave packet resumes the Gaussian form frequently. The probability thus oscillates persistently between the central peak and the ripple-rings. If the initial Gaussian width is close to the magnetic length, the wave packet retains the Gaussian form and its height and width oscillate with a period determined by the first Landau energy. The wave-packet evolution is determined jointly by the initial state and the magnetic field, through the electronic structure of graphene in a magnetic field.

quant-ph↗

arXiv2011

Damping Effect of Electromagnetic Radiation and Time-Dependent Schrodinger Equation

The inexactness of the time-dependent Schrödinger equation of a charged particle in an external electromagnetic field is discussed in terms of the damping effect of the radiation. A possible improvement is to add a nonlinear term representing this effect to the linear Schrödinger equation. Conditions for the nonlinear term are investigated and it is demonstrated that the obtained nonlinear Schrödinger equation may present state evolutions similar to the wave-function reduction and transitions between stationary states.

quant-ph↗

arXiv2003

Spatially Differential Forms of Lenz Law

Two sets of spatially differential formulas of Lenz law on electromagnetic inductance are presented. They are a cut-magnetic flux induced voltage, which instantaneously results from cutting magnetic flux as a conductor moving with respect to an external magnetic field, and a wave-induced voltage due to the interaction of a conductor or charged particles with the arriving electromagnetic wave, which is originated from a changing magnetic flux source. Upon the Lenz differential forms, the induced electrical field strength, relevant properties and their application are discussed.

physics.gen-ph↗

arXiv2003

Lorentz Force Correction and Radiation Frequency Property of Charged Particles in Magnetic Dipole

By concern of compression of charge density field, the corrected Lorentz force formula and consequent inference is presented. And further radiation frequency property of an individual charge density field in magnetic dipole is analyzed respectively for radiant property of the charged particle and the emitted electromagnetic wave transfer property between the moving radiant source and observer. As results, the behavior and radiation frequency property of the electron beam in magnetic dipole is interpreted upon the individual's behavior and property. At final, the potential application is put forward for wider interest.

physics.acc-ph↗

arXiv2003

Energy Differential Structure and Exchange of A Micro Flux Increment of Charged Particles in Longitudinal Acceleration

Differential energy structure of a micro multi-charged-particle system and the beam internal potential energy is derived with consequent property and ecessary inference. Then by combining the energy differential structure with differential transfer relations of physical flux density between different time domains, we present a general explicit formula for energy exchange in the beam element's transfer or accelerating process between source and observer, further give an analysis on relativistic beam's mass-energy relation and beam's energy up limits for resonant frequency (rf) and DC acceleration. Finally we discuss the property of elementary charge density field and consequences.

physics.acc-ph↗

arXiv2003

Differential Transfer Relations of Physical Flux Density Between Time Domains of the Flux Source and Observer

Differential transfer relations of flux density, general physics quantities' and its corresponding energy's, between time domains of source and observer are derived from conservative rule of various physical quantities and time function between the two domains. In addition, integrated form of the relations are inferred and examples of potential application are illustrated and discussed.

physics.acc-ph↗

arXiv2003

Phase Difference Function in Coherent Temporal-spatial Region and Unified Equations of Steady, Non-steady Interference

Phase difference function is established by means of phase transfer function between time domains of source and interference point. The function reveals a necessary interrelation between outcome of two-beam interference, source's frequency and measured subject's kinematic information. As inference unified equations on steady and non-steady interference are derived. Meanwhile relevant property and application are discussed.

physics.optics↗