Abstract
Extreme in-plane upper critical magnetic fields strongly violating the Pauli paramagnetic limit have been observed in the misfit layer and single crystals with and 5.7 K, respectively. The crystals show a two-dimensional to three-dimensional transition at temperatures slightly below with an upturn in the temperature dependence of , a temperature-dependent huge superconducting anisotropy and a cusplike behavior of the angular dependence of . Both misfits are characterized by a strong charge transfer from LaSe to . As shown in our previous work, is electronically equivalent to the highly doped monolayers. Then, the strong upper critical field can be attributed to the Ising coupling recently discovered in atomically thin transition metal dichalcogenides with strong spin-orbit coupling and a lack of inversion symmetry. A very similar behavior is found in , where the charge transfer is nominally twice as big, which could eventually lead to complete filling of the conduction band and opening superconductivity in LaSe. Whatever the particular superconducting mechanism would be, a common denominator in both misfits is that they behave as a stack of almost decoupled superconducting atomic layers, proving that Ising superconductivity can also exist in bulk materials.
- Received 8 July 2021
- Revised 9 November 2021
- Accepted 30 November 2021
DOI:https://doi.org/10.1103/PhysRevB.104.224507
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