Science & Technology, Canada (Commonwealth Union) – Strange metals are a type of materials that exhibit unusual electrical and thermal properties that are not easily explained by traditional theories of metals. They are typically characterized by a linear or “bad” metallic behavior, meaning that their electrical resistance increases linearly with temperature, unlike normal metals which exhibit a quadratic increase in resistance with temperature. This linear increase in resistance is also accompanied by an unusual behavior of the electrical conductivity, which does not follow the normal rules for metallic conductivity. It is believed that strange metals are related to the interaction of electrons with strong quantum fluctuations in the material.
Researchers at the University of Toronto (U of T) may be one step closer to knowing the nature of strange metals, despite its puzzling nature.
Electrons are subatomic particles that carry a negative electric charge and are part of the family of particles called leptons. They are one of the fundamental building blocks of matter and are found in the electron cloud or shell that surrounds the nucleus of an atom.
Electrons play a crucial role in many physical phenomena, including electricity, magnetism, and chemical bonding. They are responsible for the electrical conductivity of metals and the flow of electricity in circuits. They are also involved in chemical reactions, where they participate in the formation and breaking of chemical bonds between atoms.
Researchers pointed out that for quantum matter, in comparison, electrons do not engage as they would with normal materials. They are more powerful and the 4 fundamental properties of electrons that include charge, spin, orbit and lattice, become intertwined, leading to complex states of matter.
“In quantum matter, electrons shed their particle-like character and exhibit strange collective behaviour,” says condensed matter physicist Arun Paramekanti, a professor in the U of T department of physics in the Faculty of Arts & Science who further indicated that these materials are referred to as non-Fermi liquids where the simple rules break down.
Presently, 3 researchers from the department of physics and Centre for Quantum Information & Quantum Control (CQIQC) have formed a theoretical model that defines the engagements between subatomic particles in non-Fermi liquids. The framework goes further on current models and would assist researchers better know the behavior of these “strange metals.”
The findings were published in the journal Proceedings of the National Academy of Sciences (PNAS), with lead author is physics PhD student Andrew Hardy, as well as the co-authors Paramekanti together with post-doctoral researcher Arijit Haldar.
“What we’ve done is construct a model, a tool, to study non-Fermi liquid behaviour. And specifically, to deal with what happens when there is symmetry breaking, when there is a phase transition into a new type of system,” said Hardy.
“Symmetry breaking” generally defines the fundamental process observed in all of nature. Symmetry breaks as a system, which can be a droplet of water or the entire universe, as it loses its symmetry together with its homogeneity becoming more complex.
“Symmetry breaking in non-Fermi liquids is much more complicated to study because there isn’t a comprehensive framework for working with non-Fermi liquids,” added Hardy further indicating that defining the way this symmetry breaking occurs is difficult.
Researchers further indicated that with a non-Fermi liquid, engagements between electrons become more powerful when the particles are on the edge of symmetry breaking. Similar to a ball positioned at the top of a hill, where a simple nudge in either way will move it in opposite directions.
The recent findings give insight into these transitions in non-Fermi liquids and could bring about new ways to tune and grasp the properties of quantum materials. Even though it remains a serious obstacle for physicists, the work is significant for the new quantum materials that may bring about the next generation of quantum technology.
