Berlin, Dec 27 (PTI) Scientists, including one of Indianorigin, have found an exotic state of matter where theconstituent particles pair up when limited to two dimensions.
The finding, published in the journal Science, may holdimportant clues to the intriguing phenomena ofsuperconductivity, researchers said.
Superconductors are materials through which electricitycan flow without any resistance once they are cooled below acertain critical temperature.
Researchers performed experiments in which they confineda gas of ultracold atoms in two-dimensional traps which theycreated using focused laser beams.
"In solid-state materials like copper oxides, there aremany different effects and impurities that make thesematerials difficult to study," said Puneet Murthy, a PhDstudent at Heidelberg University in Germany.
"That is why we use ultracold atoms to simulate thebehaviour of electrons in solids. This allows us to createvery clean samples and gives us full control over theessential system parameters," said Murthy.
The technologically most relevant class of materials,with exceptionally high critical temperatures forsuperconductivity, is poorly understood so far.
However, there is evidence that in order forsuperconductivity to occur, a certain type of particles - thefermions - must pair up.
Moreover, research has shown that materials which becomesuperconducting at relatively high temperatures have layeredstructures.
"This means that electrons in these systems can only movein two-dimensional planes," said Selim Jochim, professor atHeidelberg University.
"What we did not understand until now was how theinterplay of pairing and dimensionality can lead to highercritical temperatures," said Jochim.
Using a technique known as radio-frequency spectroscopy,the researchers measured the response of the atoms to aradio-wave pulse.
From this response, they could tell exactly whether ornot the particles were paired and in what way.
These measurements were also performed for differentstrengths of interaction between fermions.
In the course of the experiments, the researchersdiscovered an exotic state of matter. Theory states thatfermions with a weak interaction should pair up at thetemperature at which they become superconductive.
However, when the scientists increased the interactionbetween fermions, they found that pairing occurred attemperatures several times higher than the criticaltemperature.
"To achieve our ultimate goal of better understandingthese phenomena, we will start with small systems that we puttogether atom by atom," said Jochim. PTI SARSAR.
This is unedited, unformatted feed from the Press Trust of India wire.