Scientists at the University of Bristol, led by Professor Nigel Hussey, have discovered a rare phenomenon in purple bronze, a unique one-dimensional metal, that could be key to creating a ‘perfect switch’ in quantum devices. The material can flip between being an insulator and a superconductor, a versatility known as ’emergent symmetry’. This could offer an ideal On/Off switch in future quantum technology. The research, which began 13 years ago, was published in Science. The team included Dr Piotr Chudzinski, now a Research Fellow at Queen’s University Belfast, and PhD students Xiaofeng Xu, Nick Wakeham, and Maarten Berben.
Discovery of a Rare Phenomenon in Quantum Science
Quantum scientists have identified a unique occurrence that could be instrumental in the development of a flawless switch in quantum devices. This switch would be capable of transitioning between an insulating state with zero conductivity and a superconducting state with unlimited conductivity. This discovery was made in a one-dimensional metal known as purple bronze, which is made up of individual conducting chains of atoms.
The phenomenon, known as ’emergent symmetry’, could be triggered by minor changes in the material, such as a small stimulus like heat or light. This could result in an instant transition from an insulating state to a superconducting state, and vice versa. This discovery could potentially offer an ideal On/Off switch in future quantum technology developments.
The Role of Purple Bronze in Quantum Science
The research, conducted by the University of Bristol, found that these two opposing electronic states exist within purple bronze. In the absence of a magnetic field, the resistance of purple bronze was highly dependent on the direction in which the electrical current is introduced. Its temperature dependence was also rather complicated.
Around room temperature, the resistance is metallic, but as the temperature is lowered, this reverses and the material appears to be turning into an insulator. Then, at the lowest temperatures, the resistance plummets again as it transitions into a superconductor. Despite this complexity, surprisingly, the magnetoresistance was found to be extremely simple.
The Journey of Discovery
The journey of this discovery began 13 years ago when two PhD students measured the magnetoresistance of purple bronze. However, the data lay dormant and unpublished for the next seven years due to the lack of a coherent explanation for this puzzling behaviour.
In 2017, a physicist proposed that the resistive upturn may be caused by interference between the conduction electrons and elusive, composite particles known as ‘dark excitons’. This theory was tested and confirmed through subsequent measurements.
Emergent Symmetry: A World-First in Quantum Science
The concept of emergent symmetry is an unusual state of affairs and its development in a metal as the temperature is lowered would constitute a world-first. Physicists are familiar with the phenomenon of symmetry breaking, which involves lowering the symmetry of an electron system upon cooling. However, the converse is an extremely rare, if not unique, occurrence.
Emergent symmetry can be likened to a magic trick where a dull, distorted figure transforms into a beautiful, perfectly symmetric sphere. In this case, the figure is the material, purple bronze, and the magician is nature itself.
Future Implications of the Discovery
This discovery has significant implications for the future of quantum technology. It might be possible to exploit this ‘edginess’ to create switches in quantum circuits whereby tiny stimuli induce profound, orders-of-magnitude changes in the switch resistance.
This could potentially offer an ideal On/Off switch in future quantum technology developments. The research is a significant step forward in the field of quantum science and could pave the way for more advanced quantum devices in the future.
“Lead author Nigel Hussey, Professor of Physics at the University of Bristol, said: “It’s a really exciting discovery which could provide a perfect switch for quantum devices of tomorrow. The remarkable journey started 13 years ago in my lab when two PhD students, Xiaofeng Xu and Nick Wakeham, measured the magnetoresistance – the change in resistance caused by a magnetic field – of purple bronze.”
“Finding no coherent explanation for this puzzling behaviour, the data lay dormant and published unpublished for the next seven years. A hiatus like this is unusual in quantum research, though the reason for it was not a lack of statistics,” Prof Hussey explained.
Prof Hussey said: “In the seminar Chudzinski proposed that the resistive upturn may be caused by interference between the conduction electrons and elusive, composite particles known as ‘dark excitons’. We chatted after the seminar and together proposed an experiment to test his theory. Our subsequent measurements essentially confirmed it.”
Prof Hussey said: “Such physical symmetry is an unusual state of affairs and to develop such symmetry in a metal as the temperature is lowered, hence the term ‘emergent symmetry’, would constitute a world-first.”
Dr Chudzinski, now a Research Fellow at Queen’s University Belfast, said: “Imagine a magic trick where a dull, distorted figure transforms into a beautiful, perfectly symmetric sphere. This is, in a nutshell, the essence of emergent symmetry. The figure in question is our material, purple bronze, while our magician is nature itself.”
Prof Hussey added: “After Maarten’s Herculean effort, the story was complete and the reason why different crystals exhibited such wildly different ground states became apparent. Looking ahead, it might be possible to exploit this ‘edginess’ to create switches in quantum circuits whereby tiny stimuli induce profound, orders-of-magnitude changes in the switch resistance.”
Summary
Scientists at the University of Bristol have discovered a unique property in a one-dimensional metal called purple bronze that could potentially be used to create a perfect switch in quantum devices. The metal can instantly transition from an insulating state with zero conductivity to a superconductor with unlimited conductivity, and vice versa, a phenomenon known as ’emergent symmetry’, which could be triggered by small stimuli like heat or light.
- Quantum scientists from the University of Bristol have discovered a rare phenomenon in a unique one-dimensional metal called purple bronze, which could be key to creating a ‘perfect switch’ in quantum devices.
- The phenomenon, known as ’emergent symmetry’, allows the metal to flip between being an insulator with zero conductivity and a superconductor with unlimited conductivity, potentially offering an ideal On/Off switch in future quantum technology.
- The research was led by Professor Nigel Hussey, who began the study 13 years ago with PhD students Xiaofeng Xu and Nick Wakeham.
- The team found that the resistance of purple bronze was highly dependent on the direction of the electrical current and temperature. At room temperature, the resistance is metallic, but as the temperature is lowered, it becomes an insulator, then a superconductor at the lowest temperatures.
- The research lay dormant for seven years until a seminar by physicist Dr Piotr Chudzinski in 2017, who proposed that the resistive upturn may be caused by interference between the conduction electrons and composite particles known as ‘dark excitons’.
- Further tests were conducted by another PhD student, Maarten Berben, at Radboud University, confirming the theory.
- The findings were published in the journal Science.