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Quantum breakthrough paves way for ‘perfect switch’ in electronic devices

In a groundbreaking revelation, quantum scientists at the University of Bristol have uncovered a rare phenomenon within purple bronze that could pave the way for a revolutionary ‘perfect switch’ in quantum devices, announced in a university release.

Published in the prestigious journal Science, the research explores the emergence of a unique polarized versatility within the one-dimensional metal, offering the potential for a seamless transition between insulator and superconductor states.

The remarkable journey of discovery

The journey to this discovery began 13 years ago when two Ph.D. students, Xiaofeng Xu, and Nick Wakeham, measured the magnetoresistance of purple bronze. The material’s resistance exhibited a complex behavior, shifting from metallic to insulating states with temperature changes. Surprisingly, the magnetoresistance remained simple and consistent, raising unanswered questions for seven years.

“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,” explained lead author Nigel Hussey, Professor of Physics at the University of Bristol.

In 2017, Professor Hussey attended a seminar by physicist Dr. Piotr Chudzinski, focusing on purple bronze, a material seldom discussed in academic circles. Dr. Chudzinski proposed that the resistive upturn in the material might be linked to interference between conduction electrons and elusive composite particles known as ‘dark excitons.’ Subsequent experiments confirmed this theory, leading to the resurrection of Xu and Wakeham’s dormant data.

Quoting Professor Hussey: “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.”

Decoding emergent symmetry

The concept of ’emergent symmetry’ challenges conventional understanding, as symmetry breaking is a common phenomenon in physics. However, the reverse, where complexity transforms into symmetry, is exceedingly rare. Dr. Chudzinski likens it to a magic trick:

“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.”

To validate the theory, another PhD student, Maarten Berben, investigated 100 individual crystals, some insulating and others superconducting. The results supported the hypothesis, revealing that the emergent symmetry was responsible for the diverse ground states of different crystals.

Quoting Professor Hussey: “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.”

The discovery opens new avenues for developing quantum technology, offering the potential for highly efficient and versatile quantum devices. As researchers delve deeper into the applications of emergent symmetry, the future of quantum technology seems brighter than ever before.

In summary, the University of Bristol’s research into purple bronze has unveiled a rare and exciting phenomenon and set the stage for a quantum technological revolution. The journey from the initial perplexing data to the collaborative breakthrough with Dr. Chudzinski showcases the serendipitous nature of scientific discovery. As the scientific community eagerly awaits further developments, the promise of a ‘perfect switch’ in quantum devices looms, potentially reshaping the technology landscape in future years.


Upon cooling, condensed-matter systems typically transition into states of lower symmetry. The converse—i.e., the emergence of higher symmetry at lower temperatures—is extremely rare. In this work, we show how an unusually isotropic magnetoresistance in the highly anisotropic, one-dimensional conductor Li0.9Mo6O17 and its temperature dependence can be interpreted as a renormalization group (RG) flow toward a so-called separatrix. This approach is equivalent to an emergent symmetry in the system. The existence of two distinct ground states, Mott insulator and superconductor, can then be traced back to two opposing RG trajectories. By establishing a direct link between quantum field theory and an experimentally measurable quantity, we uncover a path through which emergent symmetry might be identified in other candidate materials.


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