A Chinese joint team revealed the anomalous thermoelectric effects of ZrTe5 in and beyond the quantum limit. The results were published in Physical Review Letters.

Zirconium pentatellurides have attracted considerable interest as topological materials very close to the boundary of topological phase transition.

In addition to its nature of multiple topological phases, a moderate magnetic field is enough to drive this layered material into the quantum limit, in which all carriers occupy the lowest Landau band.

It provides a platform to explore the exotic quantum phenomena caused by unique band topology in extremely strong magnetic fields.

The research team studied the thermoelectric effects (thermo power and Nernst effect) of ZrTe5 in strong magnetic field.  

The presence of the nontrivial electrons led to the anomalous Nernst effect and quasi linear field dependence of thermo power below the quantum limit.

In the strong-field quantum limit, they found that both the thermo power and Nernst signal exhibited exotic peaks. At higher magnetic fields, the Nernst signal had a sign reversal at a critical field where the thermo power approached zero.

Further numerical calculations showed that these anomalous behaviors could be attributed to the gap closing of the zeroth Landau bands in topological materials with the band inversion.

These findings opened a new avenue for exploring Dirac physics in topological materials.

This joint work was conducted by Dr. ZHANG Jinglei and Prof. TIAN Mingliang from High Magnetic Filed Laboratory, Chinese Academy of Sciences, Prof. WANG Chunming from Shanghai Normal University and Prof. LU Haizhou from Southern University of Science and Technology.

This work was supported by the Natural Science Foundation of China, the Youth Innovation Promotion Association CAS, the Scientific Instrument Developing Project of the Chinese Academy of Sciences and the Innovative Program of Development Foundation of Hefei Center for Physical Scienceand Technology.

High-field measurements of (a) thermo power-Sxx and (b) Nernst effect Sxy up to 33 T atseveral temperatures. (c) The band bottoms of the Landau bands vs the magnetic field. The top-right figure shows a photograph of the device in water cooling magnet. (Image by ZHANG Jinglei)