Emergent quasi-two-dimensional metallic state derived from the Mott-insulator framework

Recent quasi-two-dimensional (quasi-2D) systems with judicious exploitation of the atomic monolayer or few-layer architecture exhibit unprecedented physical properties that challenge the conventional wisdom on condensed matter physics. Here we show that the infinite layer SrCuO2 (SCO), a topical cuprate Mott insulator in bulk form, can manifest an unexpected metallic state in the quasi-2D limit when SCO is grown on TiO2terminated SrTiO3 (STO) substrates. The sheet resistance does not conform to Landau's Fermi liquid paradigm. Hard x-ray core-level photoemission spectra demonstrate a definitive Fermi level that resembles the hole doped metal. Soft x-ray absorption spectroscopy also reveals features analogous to those of a hole doped Mott insulator. Based on these results, we conclude that the hole doping does not occur at the interfaces between SCO and STO; instead, it comes from the transient layers between the chain-type and the planar-type structures within the SCO slab. The present work reveals a metallic state in the infinite layer SCO and invites further examination to elucidate the spatial extent of this state.

Automated summary

Recent studies have shown that quasi-two-dimensional (quasi-2D) systems with atomic monolayer or few-layer architecture exhibit unprecedented physical properties that challenge conventional theories in condensed matter physics. In this study, it was found that the infinite layer SrCuO2 (SCO) can exhibit an unexpected metallic state when grown on SrTiO3 substrates. This metallic state does not conform to the traditional Landau's Fermi liquid paradigm. Furthermore, it was discovered that the hole doping in SCO does not occur at the interfaces between SCO and STO, but rather from transient layers within the SCO slab.