Electronic Transport and Fermi Surface Topology of Zintl Phase Compound SrZn2Ge2

TL;DR

This study investigates the electronic transport properties and Fermi surface topology of SrZn2Ge2, revealing metallic behavior, multiband conduction, and topological surface states, with implications for understanding its quantum transport phenomena.

Contribution

It provides a comprehensive analysis combining experimental transport measurements and first-principles calculations, uncovering topological surface states and complex Fermi surface features in SrZn2Ge2.

Findings

Metallic resistivity with T^2 dependence below 35 K

Resistivity plateau below 10 K persisting under magnetic fields

Presence of topological surface states within the bulk gap

Abstract

We report a comprehensive study on the electronic transport properties of SrZn2Ge2 single crystals. The electrical resistivity of the compound exhibits metallic behavior, following a T^2 dependence below 35 K, consistent with the Fermi liquid behavior. However, a notable deviation is observed from this behavior at lower temperatures as a pronounced resistivity plateau emerges below 10 K. This plateau is remarkably robust, and persists under the magnetic fields of up to 10 T. Both the transverse and longitudinal magnetoresistance exhibit a crossover at critical field B* from weak-field quadratic-like to high-field unsaturated linear field dependence at low temperatures (T \leq 50 K). Possible sources of linear magnetoresistance are discussed based on the Fermi surface topology, classical and quantum transport models. The Hall resistivity data establish SrZn2Ge2 as a multiband system with contributions from both the electrons and holes. The Hall coefficient is observed to decrease with increasing temperature and magnetic field, changing its sign from positive to negative. The negative Hall coefficient observed at low temperatures in high fields and at high temperatures over the entire field range suggests that the highly mobile electron charge carriers dominate the electronic transport. Our first-principles calculations show that nontrivial topological surface states exist in SrZn2Ge2 within the bulk gap along the Gamma-M path. Notably, these surface states extend from the valence to conduction band with their number varying based on the Sr and Ge termination plane. The Fermi surface of the compound exhibits a distinct tetragonal petal-like structure, with one open and several closed surfaces. Overall, these findings offer crucial insights into the mechanisms underlying the electronic transport of the compound.