Scientists discover unknown mechanism of heat conduction in quantum material
The ability to conduct heat is one of the most fundamental properties of matter, crucial for engineering applications. Scientists know well how conventional materials, such as metals and insulators, conduct heat. However, things are not as straightforward under extreme conditions such as temperatures close to absolute zero combined with strong magnetic fields, where strange quantum effects begin to dominate. This is particularly true in the realm of quantum materials. Researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), University of Bonn, and Centre national de la recherche scientifique (CNRS) now exposed the semimetal zirconium pentatelluride (ZrTe5) to high magnetic fields and very low temperatures. They found dramatically enhanced heat oscillations caused by a novel mechanism. This finding challenges the widely held belief that magnetic quantum oscillations should not be detectable in the heat transport of semimetals, as the scientists report in the journal PNAS.
The quantum material ZrTe5 belongs to the class of so-called topological semimetals. In physics, the term “topological” describes special materials that, due to their unique electronic structure, have extremely robust (“topologically protected”) conduction properties. In such materials, quantum effects can lead to unconventional and often bizarre phenomena that could play a crucial role in advancing future quantum technologies. Notably, both research and industry are currently investing considerable effort into developing quantum computers, with topological materials emerging as a promising avenue for their realization. Like ZrTe₅: it combines a rare set of non-trivial electronic properties, making it potentially relevant for high-precision electronics applications and magnetic-field sensor technologies.
“When a normal metal such as silver or copper is placed in strong magnetic fields at temperatures close to absolute zero, that is −273.15 °C, its heat conduction is expected to oscillate − a striking example of quantum mechanical dynamics of electrons in metals. This effect arises due to the existence of the so-called Fermi surface, a boundary between occupied and unoccupied energy states of electrons in a metal”, Dr. Stanisław Gałeski, currently assistant professor at Radboud University and visiting scientist at the Dresden High Magnetic Field (HLD) laboratory at HZDR, explains. “On the other hand, in semimetals, there are very few electrons available to transport heat, and as such, heat conduction is widely believed to be dominated by phonons − emergent particles that represent crystal lattice vibrations. As such, quantum oscillations should not be detectable in the transport of heat”, Gałeski sums up more traditional expectations. However, several recent experiments have found giant quantum oscillations in the heat conduction of semimetals, questioning the mechanism of heat transport.
Read more on HZDR website
Image: Artistic visualization of a crystalline rod made of the semimetal ZrTe5. There is a heat gradient from one end to the other. In its center, giant oscillations in its heat conduction are toggled by the magnetic field, which is generated by the electromagnet below.
Credit: B. Schröder/HZDR