For the first time, a temperature-driven contour change in an electron behavioral map—known as the Fermi surface—has been reported. The key properties of conducting materials are determined by the behavior of the electrons that reside on so called “Fermi surface.” Changes in the shape of this surface, known as Lifshitz transitions, previously were seen only when substantial pressure was applied or the chemical composition of the material was modified. Employing a technique that uses light energy (photons) to study electron properties within a sample, known as angle-resolved photoemission spectroscopy (ARPES), researchers found that in a compound of tungsten and tellurium such a Lifshitz transition occurs by merely changing the temperature. Researchers found that upon an increase of the temperature the electron pockets remain intact, while the hole pockets vanished above 165 K (-162.67 °F). Researchers are studying this material and its cousins because of their unusual and dramatic resistance change (500,000%!) in a magnetic field. The discovery of a temperature-driven Lifshitz transition is key to understanding many other semimetallic quantum materials that hold promise for revolutionizing data storage and information technology.
Shown is the temperature dependence of the band dispersion at the hole pocket divided by the Fermi function. Researchers found that upon increase of the temperature the electron pockets remain intact, while the hole pockets vanished above 165 K. The pink arrow points to a band located above the hole band.
Temperature induced Lifshitz transition in WTe2