Inorganic chiral crystals have attracted much recent interest for their potential topological quantum properties1. In particular, β-Ag2Te was shown to be a bulk insulator hosting a topological surface state (TSS) of highly anisotropic Dirac dispersion2. On the other hand, in chiral materials, an electric current along the helical axis produces a collinear spin polarization; this is known as chirality-induced spin selectivity (CISS)3. This raises the intriguing possibility that Ag2Te may be a material that simultaneously exhibits TSS and CISS. Here we report on electrical transport measurements on oriented films of nonmagnetic Ag2+δTe. The films were grown by electron-beam evaporation on quartz, which were shown to be highly textured by XRD. With decreasing temperature, the film resistivity shows semiconducting behavior at high temperatures, and plateaus below ~50 K, consistent with the predominance of a TSS (Fig. 1). The in-plane field magnetoresistance (MR) of the samples exhibits qualitatively different behavior for the longitudinal and transverse configurations. The transverse MR is positive and of a similar magnitude to polycrystalline Ag2Te samples4. In contrast, the longitudinal MR is negative in the semiconducting temperature range, and remains substantial at 300 K. At lower temperatures, the longitudinal MR shows a non-monotonic behavior, with sign reversals for the slope and even magnitude with increasing field (Fig. 2). The unusual MR in the oriented films of Ag2+δTe implies two competing mechanisms behind the magnetotransport properties of Ag2+δTe, possibly reflecting the coexistence of a TSS on the surface and CISS in the bulk. *Work supported by NSF grant DMR-1905843

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Sign Reversal and Large Anisotropy in the Magnetoresistance of Oriented Thin Films of Ag2+δTe

Sign Reversal and Large Anisotropy in the Magnetoresistance of Oriented Thin Films of Ag2+δTe

**Session chairs:** Yu-hang Li, University of California, Riverside and Lambert Alff, TU Darmstadt


BOB - Magnetoelectronic Materials and Phenomena: 2D and Topological Materials

technical paper

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Sign Reversal and Large Anisotropy in the Magnetoresistance of Oriented Thin Films of Ag2+δTe

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