Monday, March 19, 2007

The "string-net liquid" nature of Universe and a new state of matter - 'Herbertsmithite'

Xiao-Gang Wen at the Massachusetts Institute of Technology and Michael Levin at Harvard University have come up with a prediction for a new state of matter, and even a visualisation of the nature of space-time itself. Levin presented their work at the Topological Quantum Computing conference at the University of California, Los Angeles, early this month.

Their 25-year-old experiment is turning everything we know about matter upside down. In their theory elementary particles are not the fundamental building blocks of matter. Instead, they emerge from the deeper structure of the non-empty vacuum of space-time. They predict that the entire universe could be made of a string-net liquid.

Joel Helton's group at MIT might have found a candidate for such a material: a dark green crystal called " herbertsmithite", found in the mountains of Chile in 1972. They have named it after a mineralogist they really admired, Herbert Smith". They didn't realise the potential herbertsmithite would have for physicists years later.

Herbertsmithite is unusual because its electrons are arranged in a triangular lattice. Normally, electrons prefer to line up so that their spins are in the opposite direction to that of their immediate neighbours, but in a triangle this is impossible - there will always be neighbouring electrons spinning in the same direction. Wen and Levin's model shows that such a system would be a string-net liquid.

The Herbertsmithite existing in nature contains impurities that disrupt any string-net signatures. So Helton's team made a pure sample in the lab. The team measured the degree of magnetisation in the material, in response to an applied magnetic field. If herbertsmithite behaves like ordinary matter, they argue, then below about 26 °C the spins of its electrons should stop fluctuating - a condition called magnetic order. But the team found no such transition, even down to just a fraction above absolute zero!

This could be just a starting point for still newer forms of matter!

More >>>>

The universe is a string-net liquid

15 March 2007, New Scientist

By: Zeeya Merali

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