Basic Science

Spinning on a Gold Atom

Recently, Gao Li and other experts of the Research Group headed by Gao Hongjun from the National Laboratory for Condensed Matter Physics, Institute of Physics (IoP), CAS, made a breakthrough in the research on molecular rotors. They realized single-molecule rotors with a fixed off-center rotation axis and their large-scale ordered arrays on gold surfaces for the first time in the world. The result of this work was published on the Nov. 2008 issue of Physical Review Letters, drew wide attention among international counterparts and was selected as Editors’ Suggestion of Physical Review Letters. The Physicsof American Physical Society highlighted this result in an article entitled “Spinning on a Gold Atom”. The result also became the top story in physicsworld.com and nanotechweb.org of the Institute of Physics with the title of “Nanorotors Move Together”. This work was co-accomplished by Liu Yunqi, Research Fellow from the Institute of Chemistry, CAS and Prof. W.A. Hofer from the University of Liverpool.

Secret of Dark Matters to be Exposed

The Nov. 20 issue of Nature published a paper co-accomplished by the Purple Mountain Observatory, CAS and its foreign counterparts, entitled “An Excess of Cosmic Ray Electrons at Energies of 300-800 GeV”. It boasts the latest finding of the Purple Mountain Observatory, CAS and its foreign counterparts in the field of high-electron space observation. The observation on dark matters is currently one of the central issues in the scientific community. The Purple Mountain Observatory has begun cooperation with relevant institutions in U.S.A., Germany and Russia since 1998 in the development and continuous improvement of probe and observation on high-electron by using American Antarctic Pole long-term balloon project. They found that there is an “excess” of electrons at energies of approximately 300-800 GeV compared with the theoretical result. The analysis showed that this “excess” may arise from the annihilation of dark matter particles. The result of observation well matched the Kaluza-Klein particle model as predicted by the dark matter theory. If this result is proven to be correct, it will not only solve the issue about what dark matter is and also imply there are additional dimensions in the universe, which could lead to significant breakthrough in physics. 20 participants involved in this research, who come from 7 research institutes of China, U.S.A., Germany and Russia. The Purple Mountain Observatory is the principal unit. This achievement has drawn wide attention in international academic circles. The Magazine Nature had a special interview with Chang Jin, principal author of this article, and a special article based on the interview is also given in the same issue. Nature also made it a featured story in the “News & View” section of the same issue. The magazine Science will also specifically introduce this achievement in an article entitled “Dark Matter Story”. Besides, the British New Scientist, US New York Times,science@nasa and other media will also follow-up.

Superconductivity Sees New Progress

Recently, Research Fellows Dai Xi and Fang Zhong from the Beijing National Laboratory for Condensed Matter Physics, the Institute of Physics (IoP), CAS and Zhang Fuchun, professor from the University of Hong Kong jointly studied the important issue of pairing for superconducting LaFeAsO1-xFx. Relevant results were published on Physical Review Letters 101 (2008) 057008.

Research Fellows Dai Xi, Fang Zhong and their partners put forward a new possible mechanism of superconductivity: the spin-triplet superconducting state of even parity mediated by ferromagnetic Hund’s coupling between electrons in two almost degenerate orbital bands. The analysis showed that the randomness irrelevant to the orbit would not destroy this superconducting state. This explains why Fe-based superconductor is insensitive to the randomness caused by nonmagnetic impurities. Besides, the splitting of the orbital degeneracy suppresses superconductivity and leads to an anisotropic spectrum in the Bogoliubov quasi-particle. The latter predicts the existence of Fermi pockets, which needs to be verified by the angle resolved photoemission spectra.