Extreme in-plane upper critical magnetic fields of heavily doped quasi-two-dimensional transition metal dichalcogenides

Extreme in-plane upper critical magnetic fields \(B_{c2//ab}\) strongly violating the Pauli paramagnetic limit have been observed in the misfit layer \((LaSe)_{1.14}(NbSe_2)\) and \((LaSe)_{1.14}(NbSe_2)_2\) single crystals with \(T_c\) = 1.23 K and 5.7 K, respectively. The crystals show a two-dimen...

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Bibliographic Details
Published in:arXiv.org 2021-12
Main Authors: Samuely, P, Szabó, P, Kačmarčík, J, Meerchaut, A, Cario, L, Jansen, A G M, Cren, T, Kuzmiak, M, Šofranko, O, Samuely, T
Format: Article
Language:English
Subjects:
Anisotropy
Chalcogenides
Charge transfer
Critical field (superconductivity)
Ising model
Magnetic fields
Single crystals
Spin-orbit interactions
Superconductivity
Temperature dependence
Transition metal compounds
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Summary:Extreme in-plane upper critical magnetic fields \(B_{c2//ab}\) strongly violating the Pauli paramagnetic limit have been observed in the misfit layer \((LaSe)_{1.14}(NbSe_2)\) and \((LaSe)_{1.14}(NbSe_2)_2\) single crystals with \(T_c\) = 1.23 K and 5.7 K, respectively. The crystals show a two-dimensional to three-dimensional transition at temperatures slightly below \(T_c\) with an upturn in the temperature dependence of \(B_{c2//ab}\), a temperature dependent huge superconducting anisotropy and a cusplike behavior of the angular dependence of \(B_{c2}\). Both misfits are characterized by a strong charge transfer from LaSe to \(NbSe_2\). As shown in our previous work, \((LaSe)_{1.14}(NbSe_2)\) is electronically equivalent to the highly doped \(NbSe_2\) 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 \((LaSe)_{1.14}(NbSe_2)_2\), where the charge transfer is nominally twice as big, which could eventually lead to complete filling of the \(NbSe_2\) 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.
ISSN:2331-8422
DOI:10.48550/arxiv.2107.07302