Unconventional scaling of the superfluid density with the critical temperature in transition metal dichalcogenides.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31819897.
- Also identified by DOI 10.1126/sciadv.aav8465 and PMC identifier 6884407.
- Licence recorded as CC BY-NC.
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Abstract
We report on muon spin rotation experiments probing the magnetic penetration depth λ(<i>T</i>) in the layered superconductors in 2H-NbSe<sub>2</sub> and 4H-NbSe<sub>2</sub>. The current results, along with our earlier findings on 1T'-MoTe<sub>2</sub> (Guguchia <i>et al.</i>), demonstrate that the superfluid density scales linearly with <i>T</i> <sub>c</sub> in the three transition metal dichalcogenide superconductors. Upon increasing pressure, we observe a substantial increase of the superfluid density in 2H-NbSe<sub>2</sub>, which we find to correlate with <i>T</i> <sub>c</sub>. The correlation deviates from the abovementioned linear trend. A similar deviation from the Uemura line was also observed in previous pressure studies of optimally doped cuprates. This correlation between the superfluid density and <i>T</i> <sub>c</sub> is considered a hallmark feature of unconventional superconductivity. Here, we show that this correlation is an intrinsic property of the superconductivity in transition metal dichalcogenides, whereas the ratio <i>T</i> <sub>c</sub>/<i>T</i> <sub>F</sub> is approximately a factor of 20 lower than the ratio observed in hole-doped cuprates. We, furthermore, find that the values of the superconducting gaps are insensitive to the suppression of the charge density wave state.