Structural and Electronic Properties of Ti- and Ca-Doped Hexagonal TbInO₃

Magnetic frustration combined with strong quantum fluctuations can create a quantum spin liquid ground state in that material. Doped spin liquids, which may host novel properties such as fractionalized charges and unconventional superconductivity are of fundamental interest and may hold promise for quantum computing applications. However, understanding what happens to added charge carriers in doped spin liquids remains a challenging problem. Recent research has demonstrated that hexagonal ferroelectric TbInO₃, characterized by anisotropic exchange interactions, substantial spin-orbit coupling, and f-electron magnetism, is a candidate spin liquid material. Low-dimensional frustrated magnetism in TbInO₃ arises from its layered crystal structure, consisting of nonmagnetic layers of corner-sharing InO₅ trigonal bipyramids alternating with layers of magnetic Tb³⁺ ions arranged in a distorted triangular lattice featuring two distinct Tb sites. In this work, we employ density functional theory (DFT) calculations together with scanning transmission electron microscopy (STEM) imaging to investigate the effects of doping hexagonal TbInO₃ thin films via chemical substitution. We explicitly introduce Ti⁴⁺ for electron doping and Ca²⁺ for hole doping, systematically exploring various dopant concentrations and configurations. We investigate the evolution of the structural and ferroelectric properties of electron- and hole-doped TbInO₃, finding good agreement between changes to lattice parameters and atomic displacement amplitudes from our DFT calculations and STEM measurements We also combine DFT calculations of the density of states with electron energy loss spectroscopy measurements to probe the evolution of the electronic structure of TbInO₃ upon Ti⁴⁺ and Ca²⁺ substitution. This research provides new insight into the structural and electronic properties of doped TbInO₃ and their implications for conductivity in low-dimensional frustrated magnetic states.<br/>Funding acknowledgement: This material is based upon research supported by Air Force Office of Scientific Research (MURI Grant No. FA9550-21-1-0429).