2008 NOV 24 - (VerticalNews.com) -- "A systematic investigation of the electronic transport properties of Haeckelite nanotubes using ab initio calculation is presented," investigators in Lanzhou, People's Republic of China report.

  "The Haeckelite nanotube is coupled with Haeckelite nanotubes and bulk Au electrodes, respectively. Negative differential resistance and nonlinear conduction phenomena have been observed in the simulated I-V curves," wrote Y.F. Li and colleagues, Lanzhou University ...read more

  2008 NOV 24 - (VerticalNews.com) -- According to a study from Seoul, South Korea, "In the presence of spin-orbit coupling and inversion symmetry of the lateral confinement potential a single electron does not exhibit matrix Berry phases in quasi-two-dimensional semiconductor quantum dots. In such a system we investigate whether many-body correlation effects can lead to finite matrix Berry phases."

  "We find that the transformation properties of many-electron wavefunctions under two-dimensional inversion operation do not allow finite matrix Berry phases. This effect is exact and is independent of the form of electron-electron interactions. On the other hand, quasi-two-dimensional semiconductor quantum dots with lateral confinement potential without inversion symmetry can have finite matrix Berry phases," wrote S.C. Kim and colleagues, Korea University ...read more

  2008 NOV 24 - (VerticalNews.com) -- According to recent research from Beijing, People's Republic of China, "Using a simplified toy model, we study the quantum coherence effect in the spin-polarized transport of nano-magnets. A density matrix master equation is used to describe the correlation in the magnet."

  "Through comparison with the classical rate equation, the coherence effect is clearly demonstrated. We find that the interaction between the spin-polarized current and the nano-magnet can be tuned by changing the bias voltage. At small bias voltage, the ferromagnetic lead will induce an antiferromagnetic exchange field. This exchange field is raised from the dynamics of the nondiagonal reduced density matrix elements of the nano-magnet. It is an obvious coherence effect and is beyond the scope of the classical rate equation. When bias voltage increases, tunneling becomes important and the dominating spin control mechanism is the spin accumulation which has been well studied in recent works (Timm and Elste 2006 Phys. Rev. B 73 235304, Timm 2007 Phys. Rev. B 76 014421, Misiorny and Barnas 2007 Phys. Rev. B 76 054448, Barnas et al 2000 Phys. Rev. B 62 12363). Our results obviously imply that the coherence effect in the spin-polarized transport of the nano-magnet cannot be ignored even in the collinear structure. This phenomenon is quite different from the case of the quantum dot (QD) spin valve which means that the classical rate equation, which is widely used in the study of the QD spin valve, is invalid for the nano-magnet-based spin valve. A density matrix description becomes essential," wrote J.H. Gao and colleagues ...read more