Defects Engineering of ZrTe5 for Stabilizing Ideal Topological States

TL;DR

The study addresses inconsistent electronic and topological states in $ZrTe_5$ arising from intrinsic defects. It uses comprehensive first-principles defect calculations to map formation energies and charge states, linking defect chemistry to Fermi level control and topology via $Zr_{i}^{+}$ and $V_{Te_z}^{2-}$ defects. The findings show that defect density tunes lattice strain and thus transitions between weak and strong topological insulator states, with Te-rich growth stabilizing a nearly ideal weak TI and extrinsic doping or strain offering paths to ideal phases. This defect-engineering framework enables robust, reproducible realization of topological states in $ZrTe_5$ for quantum technologies.

Abstract

ZrTe5 is a highly tunable, high-mobility topological material that hosts a rich variety of quantum phenomena, making it a promising platform for next-generation quantum technologies. Despite intensive research efforts, experimental studies have reported inconsistent and sometimes conflicting results for its electronic and topological states, largely due to variations in sample quality. Here, through systematic frst-principles investigations of all intrinsic point defects, we identify a practical route to achieving stable and ideal topological characteristics in ZrTe5. We show that the competition between two dominant charged defects, donor-like Zr interstitials and acceptor-like Te vacancies, governs the Fermi-level position. Furthermore, variations in defect density determine the topological phases of the samples. We theoretically propose and experimentally confrm that increasing the Te/Zr ratio during crystal growth effectively suppresses intrinsic defects and stabilizes ZrTe5 in a nearly ideal weak topological insulator state. These fndings provide clear guidance for defect control and sample optimization, paving the way toward robust and reproducible realization of topological quantum states in ZrTe5 for future quantum applications.

Figures (4)

• Figure 1: (a) Reported phase: (i) electron-doped WTIs, (ii) electron-doped STIs, (iii) hole-doped STIs and (iv) hole-doped WTIs. (b) Crystal structure of ZrTe$_{5}$. Green, blue, brown and orange spheres represent Zr, Te$_z$, Te$_d$ amd Te$_a$, respectively. Schematic diagram of structure with (c) $\mathrm{Zr}_{\mathrm{i1}}^{+}$ defect and (d) $\mathrm{V}_{\mathrm{Te}_{\mathrm{z}}}^{2-}$ defect.
• Figure 2: (a) Schematic illustration of donor-like, neutral, and acceptor-like behavior of Te vacancies. (b) Band structure with the $p$ orbital contribution from the $\mathrm{Te}_{\mathrm{d}}$ and $\mathrm{Te}_{\mathrm{z}}$ atoms.(c) Charge density difference for the $\mathrm{Te}_{\mathrm{z}}$ site. Yellow and cyan indicate charge accumulation and depletion, respectively. (d) Formation energies for charged defects under Zr-rich and Te-rich conditions, respectively.
• Figure 3: (a) Strain induced by five dominant defects in $ab$ plane. (b) Band Gap as a function of strain $\varepsilon_{a}$ in PBE and HSE calculation, respectively. (c) Band gaps and topological phases of five dominant defects. (d) Strain along a axis and topological phases under various $V_{\mathrm{Te}_{\mathrm{z}}}^{2-}$ defect density (N$_{defect}$/Volume). Calculations are performed with the same number $V_{\mathrm{Te}_{\mathrm{z}}}^{2-}$ defect in 3$\times$1$\times$1, 4$\times$1$\times$1, 5$\times$1$\times$1 supercell, respectively.
• Figure 4: (a) Formation energies of intrinsic point defects evaluated at the valence-band maximum (VBM) under Te-rich conditions. (b) Schematic illustration of electronic and topological phases in ZrTe$_{5}$, arising from variations in V$_{{Te}_z}$ defect concentration. The horizontal axis qualitatively increases the Te/Zr ratio. Ideal WTI induced by extrinsic impurity in lightly $\mathrm{V}_{\mathrm{Te_z}}^{2-}$ defect sample and STI upon applying external strain to the ideal WTI. (c),(d) Temperature-dependent resistivity $\rho_{xx}$ for flux-grown ZrTe$_{5}$ with different flux ratios. (c) Normalized temperature-dependent resistivity for ZrTe$_{5}$ samples grown with different flux ratios. S74 data from Ref.exp_rho. (d) Variation of $\rho_{2K}$⁄$\rho$$_{300K}$ as a function of flux ratio.