May 19 2020
At TU Dresden, a group of physicists has identified spontaneous static magnetic fields exhibiting broken time-reversal symmetry in a family of iron-based superconductors.
Magnetic fields inside a superconductor with broken time-reversal symmetry: Red and blue arrows illustrate the direction and strength of the internal magnetic fields for forward and backward time development. Image Credit: TU Dresden.
Such a unique property drives the need to develop new theoretical models and could turn highly significant in the field of quantum computing. The outcomes of the study were recently reported in Nature Physics, a scientific journal.
In general, what happened a day earlier and what will happen a day later are two distinct and completely independent matters. In the real world, the past and the future of the life of humans are not symmetric, and thus irreversible. However, in physics, this is not the case.
In molecules, atoms, and elementary particles, the fundamental forces of nature are symmetric in relation to their development in time: forward or backward does not have any difference, and researchers name this a time-reversal symmetry.
This symmetry was also observed in all superconductors for several decades. Superconductors can be described as materials with the ability to conduct electrical currents at low temperatures, without any dissipation of energy.
The efficient generation of powerful magnetic fields, for instance, in magnetic resonance imaging (MRI) diagnosis, is one of their main applications. Of all known superconducting materials, about 99% are time-reversal symmetric.
However, in the recent past, physicists have been unearthing novel superconductors that do not conform to time-reversal symmetry. To offer an explanation for such observations, the fundamental mechanism of superconductivity, which researchers have known for over 75 years, had to be amended to a great extent.
Only these innovative superconductors exhibit the potential to spontaneously produce constant internal magnetic fields. This can result in new applications, for instance, in quantum computing devices.
Led by Dr Vadim Grinenko and Prof. Hans-Henning Klauss of the Institute of Solid State and Materials Physics at TU Dresden, an international team of researchers identified this new magnetic state with broken time-reversal symmetry in iron-based superconductors.
It is relatively simple to synthesize this unique class of intermetallic compounds. Thus, these iron-based superconductors exhibit immense potential for various applications.
In our study, we show that the iron-based superconductors discovered more than twelve years ago continue to reveal new quests for fundamental research as well as chances for new applications.
Hans-Henning Klauss, Professor, Institute of Solid State and Materials Physics, TU Dresden
Journal Reference:
Grinenko , V., et al. (2020) Superconductivity with broken time-reversal symmetry inside a superconducting s-wave state. Nature Physics. doi.org/10.1038/s41567-020-0886-9.