arXiv subjects

Yan-Feng Chen

Publications and source records attributed to Yan-Feng Chen.

59 records · Page 4Linked to original sources

arXiv2014

Photonic analogue of quantum spin Hall effect

Symmetry-protected photonic topological insulator exhibiting robust pseudo-spin-dependent transportation, analogous to quantum spin Hall (QSH) phases and topological insulators, are of great importance in fundamental physics. Such transportation robustness is protected by time-reversal symmetry. Since electrons (fermion) and photons (boson) obey different statistics rules and associate with different time-reversal operators (i.e., Tf and Tb, respectively), whether photonic counterpart of Kramers degeneracy is topologically protected by bosonic Tb remains unidentified. Here, we construct the degenerate gapless edge states of two photonic pseudo-spins (left/right circular polarizations) in the band gap of a two-dimensional photonic crystal with strong magneto-electric coupling. We further demonstrated that the topological edge states are in fact protected by Tf rather than commonly believed Tb and their pseudo-spin dependent transportation is robust against Tf invariant impurities, discovering for the first time the topological nature of photons. Our results will pave a way towards novel photonic topological insulators and revolutionize our understandings in topological physics of fundamental particles.

physics.optics↗

arXiv2014

Accidental degeneracy of double Dirac cones in a phononic crystal

Artificial honeycomb lattices with Dirac cone dispersion provide a macroscopic platform to study the massless Dirac quasiparticles and their novel geometric phases. In this paper, a quadruple-degenerate state is achieved at the center of Brillouin zone (BZ) in a two-dimensional honeycomb lattice phononic crystal, which is a result of accidental degeneracy of two double-degenerate states. In the vicinity of the quadruple-degenerate state, the dispersion relation is linear. Such quadruple degeneracy is analyzed by rigorous representation theory of groups. Using method, a reduced Hamiltonian is obtained to describe the linear Dirac dispersion relations of such quadruple-degenerate state, which is well consistent with the simulation results. Near such accidental degeneracy, we observe some unique wave propagating properties, such as defect insensitive propagating character and Talbot effect.

cond-mat.mes-hall↗

arXiv2014

Optical Analogue of Quantum Spin Hall Effect in a Two-Dimensional Gyrotropic Photonic Crystal

We propose an optical counterpart of the quantum spin Hall (QSH) effect in a two-dimensional photonic crystal composed of a gyrotropic medium exhibiting both gyroelectric and gyromagnetic properties simultaneously. Such QSH effect shows unidirectional polarization-dependent transportation of photonic topological edged states, which is robust against certain disorders and impurities. More importantly, we find that such unique property is not protected by conventional time-reversal symmetry of photons obeying the Bosonic statistics but rather by the same symmetry, as electron's time-reversal symmetry. Based on the tight-binding approximation approach, we construct an effective Hamiltonian for this photonic structure, which is shown to have a similar form to that of an electronic QSH system. Furthermore, the invariant of such model is calculated in order to unify its topological non-trivial character. Our finding provides a viable way to exploit the optical topological property, and also can be leveraged to develop a photonic platform to mimic the spin properties of electrons.

physics.optics↗

arXiv2013

Sensitively Temperature-Dependent Spin Orbit Coupling in SrIrO3 Thin Films

Spin orbit coupling plays a non-perturbation effect in many recently developed novel fields including topological insulators and spin-orbit assistant Mott insulators. In this paper, strongly temperature-dependent spin orbit coupling, revealed by weak anti-localization, is observed at low temperature in 5d strongly correlated compound, SrIrO3. As the temperature rising, increase rate of Rashba coefficient is nearly 30%-45%/K. The increase is nearly 100 times over that observed in semiconductor heterostructures. Microscopically, the large increase of Rashba coefficient is attributed to the significant evolution of effective Landé g factor on temperature, whose mechanism is discussed. Sensitively temperature-dependent spin orbit coupling in SrIrO3 might be applied in spintronic devices

cond-mat.mtrl-sci↗

arXiv2012

Nonreciprocal resonant transmission/reflection based on a one-dimensional photonic crystal adjacent to the magneto-optical metal film

We report the design of nonreciprocal resonant transmission/reflection using a one-dimensional photonic crystal (1DPC) adjacent to the magneto-optical (MO) metal film. The nonreciprocal surface modes are found at the interface between the PC and MO metal within the forbidden band of native PC structure. Breaking time-reversal symmetry using external magnetic field gives rise of such unique nonreciprocal properties. Quantitatively understanding of nonreciprocal resonant optical transmission/reflection behavior is performed using an effective admittance-matching theory. With excitation of the nonreciprocal surface modes, light can transmit and be reflected in one-way. Such design offers promising potential in realizing the optical diode.

physics.optics↗