Finding a quantum state in a natural mineral
28 Jun 2022
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Using muon spin spectroscopy, researchers have found new evidence that the mineral, szenicsite, is dominated by the novel quantum state known as the Majumdar-Ghosh point.

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Crystal structure shows the chain of Cu ions

Crystal structure of szenicsite; blue = copper, red = oxygen, white/cream = hydrogen, and pink = molybdenum.

 

​Although quantum technology may appear to be far removed from the natural world, often naturally occurring minerals show complex magnetic behaviour at low temperatures. This makes them ideal candidates for the investigation of the origin of these intriguing complexities.

The novel quantum state explored in this study, published as a letter in Physical Review B, is the Majumdar-Ghosh point, which is a situation where long-range magnetic order is suppressed in a one-dimensional system due to a superposition of ground states. The mineral szenicsite has a structure that enables such a one-dimensional magnetic structure, in the form of a chain of Cu2+ ions, isolated from side chains of the same ions.

To investigate whether the quantum behaviour typical of the MG point was observed in szenicsite, as had been predicted, research carried out by Adam Berlie (ISIS) and Ian Terry (Durham University) used muon spin spectroscopy measurements at temperatures as low as 0.1 K. They found that, at these ultra-low temperatures, the system is in a dynamic state dominated by quantum fluctuations.

Their experiments provide evidence that szenicsite does in fact sit on the Majumdar-Ghosh point where one expects quantum excitations to suppress any long-range order, revealing its potential for exploring these fascinating quantum states. 

Further information

The full paper can be found at DOI: 10.1103/PhysRevB.105.L220404

Contact: Berlie, Adam (STFC,RAL,ISIS)