Thermoelectric properties of Topological Weyl Semimetal Cu₂ZnGeTe₄

The study of topological quantum materials for enhanced thermoelectric energy conversion has received significant attention recently. Topological materials (including topological insulators and Dirac/Weyl/nodal-line semi-metals) with unique nature of band structure involving linear and regular parabolic bands near Fermi level (E$_F$) have the potential to show promising TE properties. In this article, we report the promising TE performance of a quaternary chalcogenide (Cu$_2$ZnGeTe$_4$) having non-trivial topological phase. At ambient condition, the compound is a narrow band gap (0.067 eV) semiconductor, with a TE figure of merit (ZT) 1.2. Application of 5% strain drives the system to a topologically non-trivial Weyl semi-metal with the right combination of linear and parabolic bands near E$_F$, giving rise to a reasonable ZT of 0.36. Apart from strain, alloy engineering (Sn substituted at Ge) is also shown to induce topological non-triviality. The present work demonstrates the potential of such unique semimetals for exceptional electronic transport properties and hence excellent thermoelectric performance.