Observation of superconductivity in structure-selected Ti2O3 thin films

The search for new superconductors capable of carrying loss-free current has been a research theme in condensed matter physics for the past decade. Among superconducting compounds, titanates have not been pursued as much as Cu 2+ (3 d 9 ) (cuprate) and Fe 2+ (3 d 6 ) (pnictide) compounds. Particularly, Ti 3+ -based compounds or electron systems with a special 3 d 1 filling are thought to be promising candidates as high-T C superconductors, but there has been no report on such pure Ti 3+ -based superconducting titanates. With the advent of thin-film growth technology, stabilizing new structural phases in single-crystalline thin films is a promising strategy to realize physical properties that are absent in the bulk counterparts. Herein, we report the discovery of unexpected superconductivity in orthorhombic-structured thin films of Ti 2 O 3 , a 3 d 1 electron system, which is in strong contrast to the conventional semiconducting corundum-structured Ti 2 O 3 . This is the first report of superconductivity in a titanate with a pure 3 d 1 electron configuration. Superconductivity at 8 K was observed in the orthorhombic Ti 2 O 3 films. Leveraging the strong structure-property correlation in transition-metal oxides, our discovery introduces a previously unrecognized route for inducing emergent superconductivity in a newly stabilized polymorph phase in epitaxial thin films. Superconductors: thin films reveal titanate’s hidden strength Researchers have discovered a titanate -based single-crystal film with a rare structure that allows superconductivity to emerge at low temperatures. Titanium (III) oxide, Ti 2 O 3 , has garnered recent interest for solar and energy harvesting devices because its electrons are easily excited by electromagnetic radiation. A team led by Tom Wu from University of New South Wales in Sydney, Australia and Shuai Dong from Southeast University in Nanjing, China, report that these electrons have a very high density comparable to metals and are strongly coupled with lattice in constrained thin films. The researchers used a sapphire substrate to direct the growth of nanometer-thick Ti 2 O 3 layers into a solid-state structure not normally found in free-grown crystals. One particular combination of growth temperature and film thickness yielded an orthorhombic crystal phase that exhibited an unusual semiconductor-to-superconductor electronic transition when cooled to 8 K. Polymorph-dependent superconductivity was discovered in orthorhombic-struc