Yan-Mei Yu

Stacked bilayer phosphorene: strain-induced quantum spin Hall state and optical measurement

Bilayer phosphorene attracted considerable interest, giving a potential application in nanoelectronics owing to its natural bandgap and high carrier mobility. However, very little is known regarding the possible usefulness in spintronics as a quantum spin Hall (QSH) state of material characterized by a bulk energy gap and gapless spin-filtered edge states. Here, we report a strain-induced topological phase transition from normal to QSH state in bilayer phosphorene, accompanied by band-inversion that changes number from 0 to 1, which is highly dependent on interlayer stacking. When the bottom layer is shifted by 1/2 unit-cell along zigzag/armchair direction with respect to the top layer, the maximum topological bandgap 92.5 meV is sufficiently large to realize QSH effect even at room-temperature. An optical measurement of QSH effect is therefore suggested in view of the wide optical absorption spectrum extending to far infra-red, making bilayer phosphorene a promising candidate for opto-spintronic devices.

Role of initial system-bath correlation on coherence trapping

We study the coherence trapping of a qubit correlated initially with a non-Markovian bath in a pure dephasing channel. By considering the initial qubit-bath correlation and the bath spectral density, we find that the initial qubit-bath correlation can lead to a more efficient coherence trapping than that of the initially separable qubit-bath state. The stationary coherence in the long time limit can be maximized by optimizing the parameters of the initially correlated qubit-bath state and the bath spectral density. In addition, the effects of this initial correlation on the maximal evolution speed for the qubit trapped to its stationary coherence state are also explored.

Directed self-organization of trenched templates for nanowire growth

We combine a proposed approach to fabricate self-organized nanowires, which are grown in trenched templates, with a periodic strain field of a buried misfit dislocation network or a compliant substrate to guide the kinetic roughening and coarsening process in the formation of the template. Numerical simulations of the directed self-organization process show the possibility to form perfectly ordered parallel trenches with adjustable period, which allows to grow extended nanowires.

Simultaneous step meandering and bunching instabilities controlled by Ehrlich-Schwoebel barrier and elastic interaction

Through phase-field simulations, we investigate simultaneous step meandering and bunching instabilities with the presence of Ehrlich-Schwoebel barrier and elastic interaction. The meandering instability induced by the Ehrlich-Schwoebel barrier is found to be dependent on the elastic interaction at low adatom deposition rate. The ordered step meandering-bunching structure is designed by using the predefined magnitude distribution of the force monopoles on vicinal surfaces based on interplay between the Ehrlich-Schwoebel barrier and the elastic interaction.

Dirac monopoles with a polar-core vortex induced by spin-orbit coupling in spinor Bose-Einstein condensates

We report Dirac monopoles with polar-core vortex induced by spin-orbit coupling in ferromagnetic Bose-Einstein condensates, which are attached to two nodal vortex lines along the vertical axis. These monopoles are more stable in the time scale of experiment and can be detected through directly imaging vortex lines. When the strength of spin-orbit coupling increases, Dirac monopoles with vortex can be transformed into those with square lattice. In the presence of spin-orbit coupling, increasing the strength of interaction can induce a cyclic phase transition from Dirac monopoles with polar-core vortex to those with Mermin-Ho vortex. The spin-orbit coupled Bose-Einstein condensates not only provide a new unique platform for investigating exotic monopoles and relevant phase transitions, but also can preserve stable monopoles after a quadrupole field is turned off.

Finite-field calculation of static polarizabilities and hyperpolarizabilities of In + and Sr

The finite field calculations are performed for two heavy frequency-standard candidates In

Finite-field calculation of the polarizabilities and hyperpolarizabilities of Al+

^+

Two-dimensional liquid crystalline growth within a phase-field-crystal model.

and Sr. The progressive hierarchy of electron correlations is implemented by the relativistic coupled-cluster and configuration interaction methods combined with basis set of increasing size. The dipole polarizabilities, dipole hyperpolarizabilities, quadrupole moments, and quadrupole polarizabilities are recommended for the ground state 5s

Relativistic configuration interaction calculation on the ground and excited states of iridium monoxide

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