Electronic inhomogeneity and phase fluctuation in one-unit-cell FeSe films.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38643171.
- Also identified by DOI 10.1038/s41467-024-47350-0 and PMC identifier 11032316.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
One-unit-cell FeSe films on SrTiO<sub>3</sub> substrates are of great interest owing to significantly enlarged pairing gaps characterized by two coherence peaks at ±10 meV and ±20 meV. In-situ transport measurement is desired to reveal novel properties. Here, we performed in-situ microscale electrical transport and combined scanning tunneling microscopy measurements on continuous one-unit-cell FeSe films with twin boundaries. We observed two spatially coexisting superconducting phases in domains and on boundaries, characterized by distinct superconducting gaps ( <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>Δ</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </math> ~15 meV vs. <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>Δ</mi></mrow> <mrow><mn>2</mn></mrow> </msub> </math> ~10 meV) and pairing temperatures (T<sub>p1</sub>~52.0 K vs. T<sub>p2</sub>~37.3 K), and correspondingly two-step nonlinear <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>V</mi> <mo>~</mo> <msup><mrow><mi>I</mi></mrow> <mrow><mi>α</mi></mrow> </msup> </math> behavior but a concurrent Berezinskii-Kosterlitz-Thouless (BKT)-like transition occurring at <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>T</mi></mrow> <mrow><mi>BKT</mi></mrow> </msub> </math> ~28.7 K. Moreover, the onset transition temperature <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>T</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mi>onset</mi></mrow> </msubsup> </math> ~54 K and zero-resistivity temperature <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>T</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mi>zero</mi></mrow> </msubsup> </math> ~31 K are consistent with T<sub>p1</sub> and <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>T</mi></mrow> <mrow><mi>BKT</mi></mrow> </msub> </math> , respectively. Our results indicate the broadened superconducting transition in FeSe/SrTiO<sub>3</sub> is related to intrinsic electronic inhomogeneity due to distinct two-gap features and phase fluctuations of two-dimensional superconductivity.