Superconductors with ‘zeitgeist’: When materials differentiate between the past and the future

Overview

What happened yesterday and what will happen tomorrow are usually two different and independent matters.The situation is different in microscopic physics. For elementary particles, atoms and molecules, forward or backward makes no difference. This is the so-called time-reversal symmetry.
 
For decades this symmetry was also found in all superconductors. Superconductors are materials which can conduct electrical currents at low temperatures without energy dissipation. One of their major applications is the efficient generation of strong magnetic fields, for example in magnetic resonance imaging (MRI) diagnosis. Approximately 99% of all known superconducting materials are time-reversal symmetric.
 
However, for some years, physicists have been discovering new superconductors which brake time-reversal symmetry. To explain these observations, the basic mechanism of superconductivity, which has been known for more than 75 years, had to be modified considerably. Only these novel superconductors are able to spontaneously generate constant internal magnetic fields. This can lead to new applications, for example in quantum computing devices.
 
An international research team led by Dresden Physicists Dr. Vadim Grinenko und Prof. Hans-Henning Klauss from the Cluster of Excellence ct.qmat – Complexity and Topology in Quantum Matter discovered this new magnetic state with broken time-reversal symmetry in iron-based superconductors. The synthesis of this versatile class of intermetallic compounds is comparatively simple. Therefore, these iron-based superconductors have an enormous potential for 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,” states Prof. Hans-Henning Klauss.
 
Original Publication:
V. Grinenko , R. Sarkar, K. Kihou, C. H. Lee, I. Morozov, S. Aswartham, B. Büchner, P. Chekhonin, W. Skrotzki, K. Nenkov, R. Hühne, K. Nielsch, S. -L. Drechsler, V. L. Vadimov, M. A. Silaev, P. A. Volkov, I. Eremin, H. Luetkens, and H.-H. Klauss, Superconductivity with broken time-reversal symmetry inside a superconducting s-wave state. Nat. Phys. (2020). 

Picture: © Hans-Henning Klauss