Non-centrosymmetric Weyl semimetal state and strain effect in the twisted-brick phase transition metal monochalcogenides.

Weyl semimetals are a class of gapless electronic excitation topological quantum materials upon breaking time-reversal or inversion symmetry. Here, we demonstrate the existence of the Weyl semimetal state in the non-centrosymmetric twisted-brick phase MoTe theoretically. The topological properties and strain effects of MoTe have been systematically studied based on first-principles calculations and the Wannier-based tight-binding method.

Noncentrosymmetric Weyl phase and topological phase transition in bulk MoTe.

Ideal topological materials are those stable materials with less nontrivial band crossing near the Fermi surface and a long Fermi arc. By means of first-principles calculations, here we present that the 3D monochalcogenide molybdenum telluride (-MoTe) without an inversion center shows a type-II Weyl semimetal (WSM) phase which cannot checked by symmetry index method. A total of eight Weyl points (WPs) are found in different quadrants of the Brillouin zone (BZ) of -MoTe, which guarantee a long Fermi arc.

Magnetic impurity in topological nodal loop semimetals.

We investigate the Kondo effect of a spin-1/2 magnetic impurity in a topological nodal loop semimetal, in which band touchings form a nodal loop. The Fermi surface of a nodal loop semimetal is a torus or a drum-like structure, which is determined by chemical potential. When the chemical potential μ lies at the nodal loop ([Formula: see text]), the magnetic impurity and the conduction electrons form bound states only if their coupling exceeds a critical value.

Graphene based all-optical spatial terahertz modulator.

We demonstrate an all-optical terahertz modulator based on single-layer graphene on germanium (GOG), which can be driven by a 1.55 μm CW laser with a low-level photodoping power. Both the static and dynamic THz transmission modulation experiments were carried out.

High-speed and broadband terahertz wave modulators based on large-area graphene field-effect transistors.

We present a broadband terahertz wave modulator with improved modulation depth and switch speed by cautiously selecting the gate dielectric materials in a large-area graphene-based field-effect transistor (GFET). An ultrathin Al2O3 film (∼60  nm) is deposited by an atomic-layer-deposition technique as a high-k gate dielectric layer, which reduces the Coulomb impurity scattering and cavity effect, and thus greatly improves the modulation performance. Our modulator has achieved a modulation depth of 22% and modulation speed of 170 kHz in a frequency range from 0.

Bilayer metallic nanofilms as broadband antireflection coatings in terahertz optical systems.

We present the potential of ultrathin bilayer metallic nanofilms for use as broadband antireflection coatings in the terahertz frequency range. The metallic layers are modeled using a wave-impedance matching approach. The experimental and theoretical results are in good agreement.

A novel method of terahertz spectroscopy and imaging in reflection geometry.

In reflection geometry of terahertz spectroscopy, the biological sample is usually placed on a sample window. This paper presents a novel method for eliminating the effect of the ringing, i.e.

Super-Poissonian shot noise as a probe of spin bias in mesoscopic systems.

It is proposed that super-Poissonian shot noise can be used to probe and measure the spin bias in mesoscopic systems. Current shot noise through a quantum dot coupled to two conducting leads is theoretically investigated when a pure spin bias is applied. It is found that super-Poissonian shot noise may be induced when the dot level is located within the spin bias window.

Transmission line model and fields analysis of metamaterial absorber in the terahertz band.

Metamaterial (MM) absorber is a novel device to provide near-unity absorption to electromagnetic wave, which is especially important in the terahertz (THz) band. However, the principal physics of MM absorber is still far from being understood. In this work, a transmission line (TL) model for MM absorber was proposed, and with this model the S-parameters, energy consumption, and the power loss density of the absorber were calculated.

Room-temperature ferromagnetism in pure and Co doped CeO(2) powders.

We report the room-temperature (RT) ferromagnetism (FM) observed in pure and Co doped CeO(2) powder. An insulating nonmagnetic CeO(2) single crystal, after grinding into fine powder, shows an RT-FM with a small magnetization of 0.0045 emu g(-1).