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In the unconventional superconductor Sr2RuO4, uniaxial stress along the [100] direction tunes the Fermi level through a Van Hove singularity (VHS) in the density of states, causing a strong enhancement of the superconducting critical temperature Tc. Here, we report measurements of the London penetration depth λ as this tuning is performed. We find that the zero-temperature superfluid density, here defined as λ(0)^(−2), increases by ∼15%, with a peak that coincides with the peak in Tc. We also find that the low temperature form of λ(T) is quadratic over the entire strain range. Using scanning tunneling microscopy, we find that the gap increases from ∆(0) ≈ 350 μeV in unstressed Sr2RuO4 to ∆(0) ≈ 600 μeV in a sample strained to near the peak in Tc. With a nodal order parameter, an increase in the superconducting gap could bring about an increase in the superfluid density through reduced sensitivity to defects and through reduced non-local effects in the Meissner screening. Our data indicate that tuning to the VHS increases the gap throughout the Brillouin zone, and that non-local effects are likely more important than reduced scattering.

Rights:

• http://arxiv.org/licenses/nonexclusive-distrib/1.0/
  

Keyword: Sr2RuO4, superconductivity, penetration depth, low-energy excitation

Date published: 2024-09-17

Publisher: American Physical Society (APS)

Journal:

• Physical Review B (ISSN: 24699950) vol. 110 issue. 10 L100502

Funding:

• Basic Energy Sciences DE-AC02-76SF00515
• Basic Energy Sciences DE-SC0021238
• Japan Society for the Promotion of Science JP18K04715
• Japan Society for the Promotion of Science JP21H01033
• Japan Society for the Promotion of Science JP22K19093
• Japan Society for the Promotion of Science JP15H05851
• Japan Society for the Promotion of Science JP22H01168
• Japan Society for the Promotion of Science JP15K21717
• Max-Planck-Gesellschaft
• Deutsche Forschungsgemeinschaft TRR288-422213477
• Deutsche Forschungsgemeinschaft A10
• Deutsche Forschungsgemeinschaft EXC 2147
• Deutsche Forschungsgemeinschaft 390858490
• Engineering and Physical Sciences Research Council EP/X012158/1

Manuscript type: Author's original (Submitted manuscript)

MDR DOI:

First published URL: https://doi.org/10.1103/physrevb.110.l100502

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Updated at: 2024-09-25 16:30:32 +0900

Published on MDR: 2024-09-25 16:30:32 +0900