Possible routes to superconductivity in the surface layers of V-doped Mg1−δTi2O4 through multiple charge transfers and suppression of Jahn-Teller activity

Abstract

Superconductivity in the family of spinel oxides is very rare owing to their robust Mott-insulating nature. About half a century ago, LiTi2O4 became the first reported spinel compound to show superconductivity with a 12 K transition temperature. Since then, several unsuccessful attempts were made to enhance the Tc of this family of materials. However, a very recent experiment [A. Rahaman et al., arXiv:2209.02053] has reported superconductivity at a higher temperature (below ∼16 K) in the V-doped Mg1−δTi2O4 thin surface layer while its bulk counterpart remains Mott insulating. The superconducting Tc of this material is significantly higher compared to other engineered MgTi2O4 thin films grown on different substrates. From our first-principles analysis, we have identified that Mg depletion significantly reduces Jahn-Teller (JT) activity and antiferromagnetic superexchange at the surface layer of V-doped Mg1−δTi2O4 due to considerable charge transfer between various ions. The combined effect of a degraded antiferromagnetic order and reduced JT activity weakens the “Mottness” of the system, leading to the emergence of superconductivity at higher temperatures.

Source-reported materials — not catalogue approval

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