Fermiology and transport properties of the proposed topological crystalline insulator SrAg4Sb2

TL;DR

This study combines experimental transport measurements and first-principles calculations to identify SrAg4Sb2 as a promising topological crystalline insulator with unique Fermi surface features and potential surface states.

Contribution

It provides the first comprehensive experimental and theoretical investigation confirming SrAg4Sb2 as a topological crystalline insulator candidate with detailed Fermiology analysis.

Findings

SrAg4Sb2 exhibits compensated semimetal behavior with high magnetoresistance.

Fermi surface consists of three distinct pockets with light effective masses.

Theoretical calculations confirm band inversion and potential topological surface states.

Abstract

Compared to time-reversal symmetry-protected Z2 topological insulators and Dirac/Weyl semimetals, there are significantly fewer candidates for topological crystalline insulators. SrAg4Sb2 is predicted to exhibit topological crystalline insulator behavior when considering spin-orbit coupling. In this study, we systematically investigate single crystals of SrAg4Sb2 using electrical transport and magnetic torque measurements, along with first-principles calculations. Our transport data reveals its compensated semimetal nature with a magnetoresistance up to around 700% at 2 K and 9 T. Analysis of de Haas-van Alphen oscillations uncovers a Fermi surface consisting of three distinct Fermi pockets with light effective masses. Comparison between the three-dimensional fermiology obtained from our oscillation data and the first-principles calculations demonstrates excellent agreement. This confirms the accuracy of the calculations, which indicate a band inversion centered at the {\Gamma} point and identify the existence of nontrivial tube and needle hole Fermi pockets at {\Gamma}, alongside one trivial diamond electron pocket at the T point in the Brillouin zone. Furthermore, symmetry and topology analysis results in two potential sets of topological invariants, suggesting the emergence of two-dimensional gapless Dirac surface states either on the ab planes or on both the ab planes and mirror planes, protected by crystal symmetries. Therefore, SrAg4Sb2 emerges as a promising candidate topological crystalline insulator.