What makes electrons tick? New device has answers
By Jia Hepeng
Updated: 2007-04-03 06:58

Twenty years after scientists discovered high-temperature superconductors, Chinese researchers have developed a new device to delve into the mysteries of superconductivity.

While the device the world's first VUV (Vacuum Ultraviolet) laser-based photoelectron spectrometer is a powerful tool to understand the micro world, it is also a result of the improving scientific environment in China, said Lu Yongxiang, president of the Chinese Academy of Sciences (CAS), who praised the device as an example of original work by Chinese scientists.

Photoelectron spectroscopy is currently the most powerful experimental tool to study superconductivity. A superconductor transmits electricity without resistance, so that there is no electricity loss.

Superconductors are ideal for high-voltage electricity transmission. Traditionally, materials' superconducting feature is only realized at very low temperature and this has stood in the way of using superconductors widely. However, in 1986 and 1987, both Chinese and Western scientists developed high-temperature superconductors.

This bolstered the hopes of the scientific community of finding superconductors that could function at more normal temperatures. But all attempts until now have failed.

Zhou Xingjiang, lead scientist of the team that developed the device a laser-based photoelectron spectrometer at the Institute of Physics under CAS, said the failure could be attributed to a poor understanding of the theories behind superconductivity.

"Classical physics theories have failed to explain high-temperature superconductivity and there are many mysteries surrounding superconductivity," Zhou told China Daily.

Exploring these unknown fields have dominated most of Zhou's research at the Institute of Physics, at Stanford University and the Lawrence Berkeley National Lab, Berkeley, and finally again at the Institute of Physics.

Zhou's studies focused on angle-resolved photoelectron spectrometer a device that can measure the energy of electrons and their momentum.

But Zhou found the precision of the traditional photoelectron spectrometer was less than satisfactory because of the limitation of its light source.

"Traditionally, the light source of a photoelectron spectrometer is mostly based on a technique called synchronous radiation, but this light source, besides its lack of high precision, is too sensitive to the surface of the material, " Zhou said.

When Zhou was in Berkeley, a casual reading of a new type of laser technology developed by Chinese scientists suddenly gave him the idea of combining lasers and the photoelectron spectrometer.

No one had tried to use laser as a light source for an angle-resolved photoelectron spectrometer because no laser source of the appropriate strength was available.

"It was mid-2004, when I have decided to return to China to work. While debating my research focus when back to China, I came across the paper by the Chinese scientists and got very excited" Zhou said.

By using laser as the light source, the photoelectron spectrometer can observe originally imperceptible activities of electrons with unprecedented high precision.

Immediately, Zhou contacted the authors, Xu Zuyan at CAS' Institute of Physics and Chen Chuangtian at the academy's Technical Institute of Physics and Chemistry.

A team of leading names in physics and optics was formed to tap the new equipment and the effort was actively supported and funded by the Institute of Physics and the CAS headquarters.

But besides the technical difficulties, Zhou had to face another challenge. Coming up with a new device does not leave time for quality academic papers but in Chinese academia, paper publication in premier journals has become a major criteria for evaluating scientists.

"This may explain the reluctance of many Chinese scientists to develop or modify their research," said Zhou.

Zhou was once again supported by the Institute of Physics, which decided not to evaluate the team's work on the basis of the number of academic papers it published.

With the helps of various organizations and a budget of 10 million yuan ($1.29 million), the world's first VUV laser-based angle-resolved photoelectron spectrometer was successfully developed late last year.

Initial experiments have shown a more-than-expected effect of the photoelectron spectrometer.

(China Daily 04/03/2007 page19)