Quantum effect at high-temperatures

07. December 2021.

Dr Jakša Vučičević, a researcher at the Institute of Physics, Belgrade, participated in the research during which a new quantum phenomenon was observed at a high temperature. The research is a part of the project Cold atoms, Hubbard model and Holography: Key to Strange Metals funded within the PROMIS programme of the Science Fund of the Republic of Serbia. On this project, Dr Vučičević worked with Dr Rok Žitko of the Jožef Stefan Institute in Ljubljana.

Dr Vučičević and Dr Žitko’s papers on the new types of magnetic quantum oscillations (QOs) appearing at high temperatures were singled out as editor’s suggestions in the journals Physical Review Letters and Physical Review B in November 2021 and were featured in APS Physics magazine. Why does this research draw so much attention among physicians?

‘Quantum oscillations of the electrical conductivity of materials at very low temperatures are a well-known phenomenon known as Shubnikov-de Haas (SdH), observed for the first time in 1930’, details Dr Vučičević, adding that the physical mechanism of such behaviour is evident in metals and semiconductors. However, in the recent experiment, a new type of oscillation present at high temperatures, where Shubnikov-de Haas does not occur, has been observed. The theory Dr Vučičević and Dr Žitko have developed describes this phenomenology. ‘It turns out that the main ‘ingredient’ for high-temperature Brown-Zak oscillations, is quasiparticles’ lifetime shortening, which occurs precisely at high temperatures’, emphasizes Dr Vučičević.

‘According to Heisenberg’s Uncertainty Principle, a shorter lifetime of quasiparticles understands that their energy is less certain, therefore, the processes where particles tunnel between two states of different energies become more probable. Brown-Zak oscillations (BZ) are the oscillations in the amplitude of this kind of tunnelling,’ says Dr Vučičević, declaring that the phenomenon of Brown-Zak oscillations was first experimentally observed in 2017, in graphene/hBN bilayer. The model developed by Dr Vučičević and Dr Žitko is quite different from this, so it is evident that this is a universal phenomenon which does not depend on lattice details.

‘It is still early to talk about commercial and technological applications of quantum effects at high temperatures. Nevertheless, in experimental physics, we believe that this phenomenon will be used for material diagnostics,’ professes Dr Vučičević.