A research team at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has discovered a quantum state in which water remains liquid even at extremely low temperatures. A team of experts from the University of Tokyo Institute for Solid State Physics in Japan, Johns Hopkins University in the US, and the Max Planck Institute for the Physics of Complex Systems (MPI-PKS) in Dresden, Germany, cool a given material to near absolute zero.

They discovered that the central property of atoms – their arrangement – did not “freeze” as usual, but remained in a “liquid” state. The new quantum material could serve as a model system for the development of new high-precision quantum sensors. The team recently published their findings in a journal. Nature Physics.

At first glance, quantum materials do not differ from ordinary matter, but they certainly do their job: Inside, electrons interact with extraordinary intensity, both with each other and with the atoms of the crystal lattice. This close interaction leads to powerful quantum effects that operate not only at the microscopic scale, but also at the macroscopic scale. Thanks to these effects, quantum materials exhibit remarkable properties. For example, they can conduct electricity without loss at low temperatures. Often, even small changes in temperature, pressure, or electrical voltage are enough to significantly change a material’s behavior.

In principle, magnets can also be thought of as quantum materials; after all, magnetism relies on the intrinsic spin of electrons in a material. “In a sense, these spins can behave like a fluid,” explains Professor Jochen Woznitza from the Dresden Magnetic Field Laboratory (HLD) at HZDR. “As the temperature drops, these erratic turns can freeze, much like water turns into ice.” For example, certain types of magnets, called ferromagnets, are not magnetic above their “freeze” values, or rather their order points. Only when they descend can they become permanent magnets.

high purity material

The international team set out to create a quantum state in which the atomic alignment associated with spins is disordered even at ultra-low temperatures, similar to a liquid that does not solidify even in extreme cold. To achieve this state, the research group used a special material that is a combination of the elements praseodymium, zirconium and oxygen. They hypothesized that the properties of the crystal lattice in this material would allow electron spins to interact in a special way with their orbits around atoms.

“However, the prerequisite was to have crystals of exceptional purity and quality,” explains Professor Satoru Nakatsuji of the University of Tokyo. It took a few tries, but eventually the team was able to produce crystals pure enough for their experiment: in a cryostat, in something like a super thermos, the experts gradually cooled their samples to 20 millikelvins (just one-fiftieth of a degree). above absolute zero. To see how the sample responded to this cooling process and within the magnetic field, they measured how much its length changed. In another experiment, the group recorded how the crystal responded to ultrasound waves coming directly from it.

intimate interaction

Conclusion: HLD’s ultrasound research specialist, Dr. “If the turns were sequenced, this should cause a drastic change in the behavior of the crystal, such as a sudden change in length,” explains Serhiy Zherlitsyn. “However, as we noticed, nothing happened! There was no abrupt change in length or response to ultrasound waves.” The result: the apparent interaction of spins and orbitals prevented ordering as the atoms remained in a liquid quantum state – the first time such a quantum state has been observed. Further studies in magnetic fields confirmed this assumption.

This fundamental research result may one day have practical implications: “At some point, we will be able to use the new quantum state to develop highly sensitive quantum sensors,” says Jochen Vosnica. “But to do that, we need to figure out how to systematically produce arousal in this situation.” The quantum sensor is considered a promising technology of the future. Because their quantum structure makes them extremely sensitive to external stimuli, quantum sensors can record magnetic fields or temperatures with much greater precision than conventional sensors. Source