- Chiang, P-C;
- Lin, SC;
- Chiang, C-Y;
- Ku, C-S;
- Huang, SW;
- Lee, JM;
- Chuang, Y-D;
- Lin, HJ;
- Liao, YF;
- Cheng, C-M;
- Haw, SC;
- Chen, JM;
- Chu, Y-H;
- H., T;
- Luo, C-W;
- Juang, J-Y;
- Wu, KH;
- Chang, Y-W;
- Yang, J-C;
- Lin, J-Y
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 TiO2-terminated 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.