New semimetal hits quantum bullseye

Semimetal research has just taken an important step forward with the discovery of a material that could lead to the development of advanced quantum technologies. A team of scientists from Austria and the United States proved that a semimetal they were studying could achieve a naturally quantum critical state without any external influences. A paper published in the journal ‘Science Advances’ describes the research that received support from the EU-funded EMP project.

When materials transition from one phase to another, for example, from a solid to a liquid when ice gets warmer and melts, it usually has to do with changes in temperature. However, phase transitions also happen when magnetic and superconducting states form. Scientists exploring the quantum properties of materials strive to achieve phase transitions at the absolute zero point of temperature, where quantum fluctuation occurs. When such a transition occurs, it’s called a quantum critical point. “Getting close to this point is usually extremely tricky, and you’re never entirely sure that your material would make it to the true quantum critical point,” remarks study first author Wesley Fuhrman of Johns Hopkins University in a news item posted on ‘EurekAlert!’. “Imagine a dartboard where the bullseye gets smaller and smaller as you lower the temperature.”The material under study was formed of one part cerium (Ce), four parts ruthenium (Ru) and six parts tin (Sn), and was made at EMP project partner Vienna University of Technology. Magnetic susceptibility, specific heat and inelastic neutron scattering experiments revealed that the semimetal CeRu4Sn6 was naturally quantum critical without any external influences at all.

“In our case, CeRu4Sn6 seems to be at the quantum critical point without any of that mucking around--a pristine quantum criticality where the dart always hits the bullseye,” states Fuhrman. “A material at a quantum critical point is ideally suited for manipulation, being at the precipice of multiple phases,” he added, calling attention to the importance of being able to manipulate quantum states for the development of quantum technologies.

In quantum computers – the quantum technology people are most familiar with – information is stored in qubits, whose quantum states researchers are currently struggling to control. The new semimetal seems to possess certain quantum states of great stability that aren’t easily disturbed by outside forces, making it a promising material for quantum computers. Although more research is needed, this has given the team reason to hope that other materials with these quantum states could be designed.

This is important because quantum technologies will need a great number of quantum materials to make them work, Fuhrman explains in the news item. “A car is much more than just combustion in a cylinder. To get quantum technology rolling, we need quantum refrigerators, quantum sensors, as well as the qubits at the heart of quantum computers.”

EMP (European Microkelvin Platform) is coordinated by Heidelberg University in Germany. The project, which ends in June 2023, is providing an improved platform for ultra-low temperature research focused on quantum materials and technologies.

For more information, please see:

EMP project website