Incipient antiferromagnetism in the Eu-doped topological insulator Bi${}_2$Te${}_3$

Abstract

Rare earth ions typically exhibit larger magnetic moments than transition metal ions and thus promise the opening of a wider exchange gap in the Dirac surface states of topological insulators. Yet, in a recent photoemission study of Eu-doped Bi${}_2$Te${}_3$ films, the spectra remained gapless down to $T=20\text{K}$. Here, we scrutinize whether the conditions for a substantial gap formation in this system are present by combining spectroscopic and bulk characterization methods with theoretical calculations. For all studied Eu doping concentrations, our atomic multiplet analysis of the $M_{4,5}$ x-ray absorption and magnetic circular dichroism spectra reveals a Eu${}^{2+}$ valence and confirms a large magnetic moment, consistent with a $4f^7{}^8{S}_{7/2}$ ground state. At temperatures below $10\text{K}$, bulk magnetometry indicates the onset of antiferromagnetic (AFM) ordering. This is in good agreement with density functional theory, which predicts AFM interactions between the Eu impurities. Our results support the notion that antiferromagnetism can coexist with topological surface states in rare-earth doped Bi${}_2$Te${}_3$ and call for spectroscopic studies in the kelvin range to look for novel quantum phenomena such as the quantum anomalous Hall effect.

arXiv comment15 pages, 9 figures

References in corpus (21)

• Experimental Observation of the Quantum Anomalous Hall Effect in a Magnetic Topological Insulator
• Angle-resolved photoemission spectroscopy of the cuprate superconductors
• Topological superconductors: a review
• Prediction and observation of the first antiferromagnetic topological insulator
• High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator
• Chiral Majorana edge state in a quantum anomalous Hall insulator-superconductor structure
• Multiplet ligand-field theory using Wannier orbitals
• Realization of the Axion Insulator State in Quantum Anomalous Hall Sandwich Heterostructures
• Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect
• Precise quantization of anomalous Hall effect near zero magnetic field
• Natural van der Waals heterostructural single crystals with both magnetic and topological properties
• Surface states and Rashba-type spin polarization in antiferromagnetic MnBi${}_2$Te${}_4$
• Chemical potential dependent gap-opening at the Dirac surface states of Bi2Se3 induced by aggregated substitutional Cr atoms
• Coincidence of Superparamagnetism and perfect quantization in the Quantum Anomalous Hall state
• Scaling of the Quantum Anomalous Hall Effect as an Indicator of Axion Electrodynamics
• Impurity states in the magnetic topological insulator V:(Bi,Sb)${}_2$Te${}_3$
• Why $T_c$ of (CaFeAs)${}_{10}$Pt${}_{3.58}$As${}_8$ is twice as high as (CaFe${}_{0.95}$Pt${}_{0.05}$As)${}_{10}$Pt${}_3$As${}_8$
• Racah materials: role of atomic multiplets in intermediate valence systems
• Intercalated europium metal in epitaxial graphene on SiC
• Microscopic effects of Dy-doping in the topological insulator Bi2Te3
• Realization of Stable Ferromagnetic Order in Topological Insulator: Codoping Enhanced Magnetism in 4f Transition Metal Doped Bi2Se3

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• Effects of Crystalline Disorder on Interfacial and Magnetic Properties of Sputtered Topological Insulator/Ferromagnet Heterostructures
• Experimental demonstration of a magnetically induced warping transition in a topological insulator mediated by rare-earth surface dopants
• Interface Engineering Enabled Low Temperature Growth of Magnetic Insulator on Topological Insulator
• Low-energy modeling of three-dimensional topological insulator nanostructures
• Magnetic interactions of 4$f$ electrons in the topological insulator chalcogenide Bi${}_2$Se${}_3$
• Pre-Patterned Superconducting Contacts for Clean Superconductor-Topological Material Interfaces Enabling Long-Range Josephson Coupling