We study the adiabatic quantum pumping characteristics in the graphene modulated by two oscillating gate potentials out of phase. The angular and energy dependence of the pumped current is presented. The direction of the pumped current can be reversed when a high barrier demonstrates stronger transparency than a low one, which results from the Klein paradox. The underlying physics of the pumping process is illuminated.Comment: 14 pages, 4 figure

Interference between different quantum paths can generate Fano resonance. One of the examples is transport through a quasibound state driven by time-dependent scattering potential. Previously it is found that Fano resonance occurs as a result of energy matching in one-dimensional systems.In this work, we demonstrate that when transverse motion is present, Fano resonance occurs precisely at the wavevector matching situation. Using the Floquet scattering theory, we considered the transport properties of a nonadiabatic time-dependent well both in the 2DEG and monolayer graphene structure. Dispersion of the quasibound state of a static quantum well is obtained with transverse motion present. We found that Fano resonance occurs when the wavevector in the transport direction of one of the Floquet sidebands is exactly identical to that of the quasibound state in the well at equilibrium and follows the dispersion pattern of the latter. To observe the Fano resonance phenomenon in the transmission spectrum, we also considered the pumped shot noise properties when time and spatial symmetry secures vanishing current in the considered configuration. Prominent Fano resonance is found in the differential pumped shot noise to the reservoir Fermi energy.

The authors investigated shot noise properties in the graphene-based double barriers. The shot noise with the Fano factor equal to 1∕3 is found to occur at all conductance minimums including the Dirac point, which is a combined result of Klein tunneling, resonant tunneling, and quasiparticle chirality. The similarity in the shot noise suppression between graphene and diffusive metals is interpreted by the collective contribution from noiseless open channels and Poissonian-noise closed ones in the transmission spectra. It is also found that the Fano factor shows abrupt increase when the energy gap in the dispersion is larger than 1meV.

Three new rearranged ent-kaurane-type diterpenoids (1-3) and seven new ent-kaurane-type diterpenoids (4-10) have been isolated from the liverwort Jungermannia atrobrunnea. Their structures were determined by extensive spectroscopic techniques and X-ray crystallographic analysis. The absolute configurations of these compounds were clarified by CD spectroscopic studies. Compound 1 is the first example of a rearranged ent-kaurane diterpenoid possessing a peroxide bridge.

Quantum pumping processes are accompanied by considerable quantum noise. We investigated the pumped shot noise (PSN) properties in adiabatically modulated graphene-based double-barrier structures. General expressions for adiabatically PSN in phase-coherent mesoscopic conductors are derived based on the scattering approach. It is found that comparing with the Poisson processes, the PSN is dramatically enhanced where the dc pumped current changes flow direction, which demonstrates the effect of the Klein paradox.

We use the Floquet scattering theory to study the correlation properties of the nonadiabatic pumped dc current and heat flow through a time-dependent quantum well. Electrons can transit through the quasibound state to the oscillator induced Floquet states leading to resonant tunneling effect. Virtual electron scattering processes can produce pumped heat flow, pumped shot noise and pumped heat flow noise, with presence of time and spatial reversal symmetry. When one of the Floquet levels matches the quasibound level there strikes a "Fano" resonance.

Two unusual flavonones coupled with styryl units, communins A (1) and B (2), and a new benzonaphthoxanthenone, ohioensin H (3), together with 11 known compounds, were isolated from the moss Polytrichum commune. The structures of 1-3 were assigned by spectroscopic data interpretation. The new compounds were evaluated for cytotoxicity against a small panel of cancer cell lines.

In quantum transport, interference between different tunneling paths generates a Fano resonance. The profile of the resonance spectrum reflects the quantum properties of the involved path states such as period, width, strength, and parity. By applying a time-dependent electric potential to a transport device, Floquet sidebands are formed to supply additional quantum paths enabling interference processes. When one of the Floquet sidebands coincides with a quasibound state inside a system, interference is strengthened and a Fano resonance can be observed. Such a phenomenon has been intensively studied in two-dimensional electron gasses, graphene, and other quantum systems. In this work, we extend related studies to the three-band pseudospin-1 Dirac-Weyl systems. Confined states and nonadiabatically pumped shot noise in pseudospin-1 quantum wells are studied. In comparison with graphene, we found that the three-band pseudospin-1 Dirac–Weyl quantum well confines more bound states and parities of these bound-state wavefunctions are different. These differences affect the quantum interference processes via the bound state and hence are reflected in the Fano resonance spectrum in the nonadiabatic transmission and shot noise. We attribute the overall behavioral difference between graphene and the pseudospin-1 system to the topological difference in their band structure and suggest the nonadiabatically induced Fano resonance as a promising way to diagnose deeply into wavefunction profiles of quantum systems.