Suppression and Revival of Superconducting Phase Coherence in Monolayer FeSe/SrTiO<sub>3</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 36519788.
- Also identified by DOI 10.1021/acs.nanolett.2c03587.
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Abstract
Monolayer FeSe grown on SrTiO<sub>3</sub> (FeSe/STO) is an interfacial high-temperature superconductor distinctively different from bulk FeSe. However, the superconducting phase coherence of the interface is challenging to probe due to its fragility in the atmosphere. Here, we perform <i>in situ</i> mutual inductance under ultrahigh vacuum on FeSe/STO in combination with band mapping by angle-resolved photoemission spectroscopy. We find that even though the monolayer shows a gap-closing temperature above 50 K, no diamagnetism is visible down to 5 K. This is the case for few-layer FeSe/STO until it exceeds a critical number of five layers, where diamagnetism suddenly appears. The suppression of diamagnetism in the monolayer is also lifted by depositing a top FeTe layer. However, <i>T</i><sub>c</sub> and superfluid density both decrease with thicker FeTe, suggesting unconventional electron pairing and phase coherence competition. Our observation may be understood by a scenario in which the interfacial superconducting phase coherence is highly anisotropic.