Basic Science

Josephson Effect for Photons Observed

Recently, a Research Team headed by Prof. Liu Wuming from the Beijing National Laboratory for Condensed Matter Physics, the Institute of Physics, CAS made a progress in the interaction between light and matter. They observed that the current flow across two weakly coupled superconductors, separated by a very thin insulating barrier, produces a new quantum effect—the Josephson effect for photons and further designed coherent photon interferometers. The results of their research were published on the Jan. 15 issue of Physical Review Letters 102，023602 (2009). Ji Anchun, postdoctoral researcher, Sun Qing, doctoral student and Professors Xie Xincheng and Liu Wuming designed an optical system that allows for direct observation of the photonic Josephson effect in two weakly linked microcavities containing ultracold two-level atoms. By moving the ultra-cold atoms within one cavity, they simulated an analogous superconducting circuit and realized both the alternating- and direct-current (ac and dc) photonic Josephson effect. They further interference devices of coherent photons. The progress is significant for further understanding of novel quantum phenomena, especially for new quantum effect in strongly coupled atom-cavity systems.

New Microscopy: Path to Understand Nano-tubes

Recently, the SF1 Team of Beijing National Laboratory for Condensed Matter Physics, CAS developed a new in-situ transmission electron microscopy measuring apparatus and realized in situ characteristics of nanotube/nanowire field effect transistor device in transmission electron microscopy. Besides determining the structure of device materials, it can also be used for in-situ measurement of electronic transport properties. They applied this method to the research on double-walled carbon nanotube and directly obtained correspondence between the electronic transport properties and chirality index of double-walled carbon nanotube. Relevant results were published on J. Am. Chem. Soc. 131, 62 (2009). The research will help understand basic physical properties and future application of double-walled carbon nanotube.

New Effect of Nano-twin Structured Copper

On Jan. 30, 2009, Science reported the achievements of a joint research result made by the Research Team led by Prof. Lu Lei from the Shenyang National Laboratory for Materials Science of the Institute of Metal Research, CAS, in joint efforts with Prof. Lu Ke from the same institute and Dr. Huang Xiaoxu from the Denmark Risφ National Laboratory. They obtained super-fine nano-structured metal using unique stable interface structure of coherence twin boundary and found the strength of the material could be increased when the thickness of twin lamellae was reduced. This finding demonstrates that when the size of pure metal is reduced to nonometer level, due to the change of plastic deformation mechanism, it will assume extreme strength and super-high work-hardened effect unavailable to general metal materials.