Scientists in Germany, including one of Indian origin, have discovered evidence of a new and exotic matter state where the constituent particles pair up when limited to two dimensions.The findings from the field of quantum physics may hold important clues to intriguing phenomena of superconductivity. The results were published in Science.
Superconductors are materials through which electricity can flow without any resistance once they are cooled below a certain critical temperature. Researchers performed experiments in which they confined a gas of ultracold atoms in two-dimensional traps which they created using focused laser beams.
Moreover, research has shown that materials which become superconducting at relatively high temperatures have layered structures. Prof. Dr. Selim Jochim of Heidelberg University’s Institute for Physics, who heads the project explained that:
This means that electrons in these systems can only move in two-dimensional planes. What we did not understand until now was how the interplay of pairing and dimensionality can lead to higher critical temperatures.
To examine this question, the scientists at the Center for Quantum Dynamics performed experiments in which they confined a gas of ultracold atoms in two-dimensional traps which they created using focused laser beams. Puneet Murthy, a Ph.D. student at Heidelberg University in Germany said that:
In solid-state materials like copper oxides, there are many different effects and impurities that make these materials difficult to study. That is why we use ultracold atoms to simulate the behaviour of electrons in solids. This allows us to create very clean samples and gives us full control over the essential system parameters.
The technologically most relevant class of materials, with exceptionally high critical temperatures for superconductivity, is poorly understood so far. However, there is evidence that in order for superconductivity to occur, a certain type of particles the fermions must pair up. Using a technique known as radio-frequency spectroscopy, the researchers measured the response of the atoms to a radio-wave pulse.
From this response, the physicists could tell exactly whether or not the particles were paired and in what way. But when the scientists increased the interaction between fermions, they found that pairing occurred at temperatures several times higher than the critical temperature. Dr. Jochim states that a proper classification of the new state of matter will require them to start with smaller systems which will be created from scratch.
The 2D traps were made using focused laser beams. The team witnessed a unique type of particle pairing and an exotic state of matter when they conducted the 2D trap experiment which strongly depends on the density of the surrounding medium (gray clouds). This suggests that in this specific exotic state, each particle is not only paired with another particle but that there are additional correlations with other particles in the environment as well.
These measurements were also performed for different strengths of interaction between fermions. In the course of the experiments, the researchers discovered an exotic state of matter. Theory states that fermions with a weak interaction should pair up at the temperature at which they become superconductive.