Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 6 of 6
Full-Text Articles in Entire DC Network
Nonlinear Optical Conductivity Of Two-Dimensional Semiconductors With Rashba Spin-Orbit Coupling In Terahertz Regime, Yee Sin Ang, J C. Cao, Chao Zhang
Nonlinear Optical Conductivity Of Two-Dimensional Semiconductors With Rashba Spin-Orbit Coupling In Terahertz Regime, Yee Sin Ang, J C. Cao, Chao Zhang
Yee Sin Ang
We reveal that two-dimensional semiconductors with Rashba spin-orbit interaction (R2DG) exhibit exceptionally strong nonlinear optical response (NOR) in the terahertz frequency regime. The spin-split of the parabolic energy band in R2DG allows strong multiple-photon process to occur via inter-subband mechanism. We show sharp multiple photon edges in the nonlinear conductivity. The edges correspond to the cut-off effect produced by the multiple-photon process. For Rashba coupling parameter of λ R ≈ 10−10 eV m, electric field strength in the order of only 102 V/cm is required for the NOR to dominate over the linear response. Furthermore, the roles of the parabolic …
Energy Loss Rate Of A Charged Particle In Hgte/(Hgte, Cdte) Quantum Wells, Qinjun Chen, Yee Sin Ang, Xiaolin Wang, R A. Lewis, Chao Zhang
Energy Loss Rate Of A Charged Particle In Hgte/(Hgte, Cdte) Quantum Wells, Qinjun Chen, Yee Sin Ang, Xiaolin Wang, R A. Lewis, Chao Zhang
Yee Sin Ang
The energy loss rate (ELR) of a charged particle in a HgTe/(HgTe, CdTe) quantum well is investigated. We consider scattering of a charged particle by the bulk insulating states in this type of topological insulator. It is found that the ELR characteristics due to the intraband excitation have a linear energy dependence while those due to interband excitation depend on the energy exponentially. An interesting quantitative result is that for a large range of the incident energy, the mean inelastic scattering rate is around a few terahertz.
Chiral-Like Tunneling Of Electrons In Two-Dimensional Semiconductors With Rashba Spin-Orbit Coupling, Yee Sin Ang, Zhongshui Ma, C Zhang
Chiral-Like Tunneling Of Electrons In Two-Dimensional Semiconductors With Rashba Spin-Orbit Coupling, Yee Sin Ang, Zhongshui Ma, C Zhang
Yee Sin Ang
The unusual tunneling effects of massless chiral fermions (mCF) and massive chiral fermions (MCF) in a single layer graphene and bilayer graphene represent some of the most bizarre quantum transport phenomena in condensed matter system. Here we show that in a two-dimensional semiconductor with Rashba spin-orbit coupling (R2DEG), the real-spin chiral-like tunneling of electrons at normal incidence simultaneously exhibits features of mCF and MCF. The parabolic branch of opposite spin in R2DEG crosses at a Dirac-like point and has a band turning point. These features generate transport properties not found in usual two-dimensional electron gas. Albeit its p Berry phase, …
Nonlinear Optical Spectrum Of Bilayer Graphene In The Terahertz Regime, Yee Sin Ang, S. Sultan, Chao Zhang
Nonlinear Optical Spectrum Of Bilayer Graphene In The Terahertz Regime, Yee Sin Ang, S. Sultan, Chao Zhang
Yee Sin Ang
We demonstrate that the nonlinear optical response in bilayer graphene is among the strongest, especially in the important frequency regime of terahertz to far-infrared. Furthermore, we show that both the single frequency and frequency tripled nonlinear response become comparable to the linear response at very moderate electric field. The field strength for the onset of nonlinear effect in bilayer graphene is well within the experimental achievable range in laboratories. Our result suggests that bilayers are preferred structures for developing graphene-based nonlinear photonics and optoelectronics devices.
Energy-Loss Rate Of A Fast Particle In Graphene, Yee Sin Ang, Chao Zhang, Chun Kee
Energy-Loss Rate Of A Fast Particle In Graphene, Yee Sin Ang, Chao Zhang, Chun Kee
Yee Sin Ang
The energy-loss rate of a fast particle in graphene is studied. The energy-loss rate always increases with increasing incident particle energy, which is quite unusual when compared to electron gas in normal metal. Graphene exhibits a “discriminating” behavior where there exists a low energy cut-off below which the scattering process is strictly forbidden, leading to lossless traverse of an external particle in graphene. This low energy cutoff is of the order of nearest neighbor hopping bandwidth. Our results suggest that backscattering is also absent in the external particle scattering of graphene.
Nonlinear Optical Response Of Graphene Superlattice In Terahertz Frequency Regime, Yee Sin Ang, Chao Zhang
Nonlinear Optical Response Of Graphene Superlattice In Terahertz Frequency Regime, Yee Sin Ang, Chao Zhang
Yee Sin Ang
We investigate the nonlinear optical response of a Kronig-Penney type graphene superlattice in which the Fermi velocity of the massless Dirac quasiparticle anisotropically depends on the direction of propagation. Such velocity anisotropy results in enhanced nonlinear optical response in terahertz frequency regime.