Deng Wen-Ji

Electronic double refraction due to the Rashba effect: Analytical and numerical results

By analogy with the classic effect of the double refraction of light, we investigate the relevant effect of an electron entering from the Non-Rashba region to the Rashba region in two-dimensional systems. It is shown that the effect of electronic double refraction is determined by a combined parameter γ = m*λFα/2πħ2, rather than both the Rashba coefficient α and wavelength λF of a Fermi electron, separately. For the case of normal incidence, the analytical expressions for the wavefunction of the electron are presented; it is predicted that the Rashba spin-orbit coupling can induce a current perpendicular to the normal incident direction of the electron. Moreover, the general case of incident electron with any given momentum and spin state are studied numerically in detail, including the abrupt changes of spin direction and the two-step characters for reflection.

Resonant tunneling through double-barrier structures on graphene

Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tight-binding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles with energy close to the Dirac points. The Klein tunneling vanishes by increasing the height of the potential barriers to more than 300 meV. The Dirac transport properties continuously change to the Schrodinger ones. It is found that the peaks of resonant tunneling approximate to the eigen-levels of graphene nanoribbons under appropriate boundary conditions. A comparison between the zigzag- and armchair-edge barriers is given.Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tight-binding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles with energy close to the Dirac points. The Klein tunneling vanishes by increasing the height of the potential barriers to more than 300 meV. The Dirac transport properties continuously change to the Schrodinger ones. It is found that the peaks of resonant tunneling approximate to the eigen-levels of graphene nanoribbons under appropriate boundary conditions. A comparison between the zigzag- and armchair-edge barriers is given.

Negative Eigenvalue Counting Method for One-Dimensional Mesoscopic Rings

Negative eigenvalue counting method has been extended to deal with the closed ring with large number of atoms threaded by a magnetic flux. This new method is extremely computer memory-saving and can be used to accurately determine the eigenvalues and eigenvectors. As numerical examples, the results of second moment and persistent current are presented.

Shot Noise in Aharonov—Casher Rings

We investigate the shot noise of electron transport through an Aharonov–Casher ring subject to the Rashba spin-orbit coupling (SOC). Analytic expressions for the coefficients of reflection and transmission are derived by using the Griffith boundary conditions. For this kind of SOC, the ballistic transport of electrons can be analyzed as two independent spin channels, and both of them have the same transmission and reflection coefficients. The dependences of shot noise and Landauer-Buttiker conductance on controllable factors, including the strength of Rashba SOC, the asymmetrical angle of lead-connection positions, the radius of the rings, and the wave vector (or energy) of the incident Fermi electrons, are explicitly described by some new combined parameters. The ways that the shot noise and conductance vary with Rashba SOC and with asymmetrical angle are demonstrated by numerical simulations, respectively. It is revealed that the shot noise reaches its maximum for the particular situation of half transmission and half reflection and zero shot noise occurs at conductance maxima.

Period Halving of Persistent Currents in Mesoscopic Möbius Ladders

We investigate the period halving of persistent currents (PCs) of non-interacting electrons in isolated mesoscopic Mobius ladders without disorder, pierced by Aharonov-Bohm flux. The mechanisms of the period halving effect depend on the parity of the number of electrons as well as on the interchain hopping. Although the data of PCs in mesoscopic systems are sample specific, some simple rules are found in the canonical ensemble average, for example, all the odd harmonics of the PCs disappear and the signals of even harmonics are non-negative.

Minimum signals in classical physics

The bandwidth theorem for Fourier analysis on any time-dependent classical signal is shown using the operator approach to quantum mechanics. Following discussions about squeezed states in quantum optics, the problem of minimum signals presented by a single quantity and its squeezing is proposed. It is generally proved that all such minimum signals, squeezed or not, must be real Gaussian functions of time.

Modified Carlsson-Gelatt-Ehrenreich Scheme for the Inverse Problem of Cohesive Energy

By using the Hardy-Wright-M?bius inverse formula, we have improved the Carlsson-Gelatt-Ehrenreich scheme for the inverse problem of cohesive energy. The advantage of the new method is that the inverse formula are in a sense independent of the geometries of lattices.

Spectral Properties of the One-Dimensional SILK Quasilattices

An one-dimensional three-tile quasilattice model is introduced. A multifractal spectral behavior has been found analytically and confirmed by the numerical simulation. The renormalization-group method has been used to study the asymptotical behavior of the spectrum, a pseudo-seven-cycle of trace map is found.