From orbital to paramagnetic pair breaking in layered superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>2</mml:mn><mml:mi>H</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>NbS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml

The superconducting transition-metal dichalcogenides <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>2</a:mn><a:mi>H</a:mi><a:mtext>−</a:mtext><a:msub><a:mi>NbSe</a:mi><a:mn>2</a:mn></a:msub></a:mrow></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>2</b:mn><b:mi>H</b:mi><b:mtext>−</b:mtext><b:msub><b:mi>NbS</b:mi><b:mn>2</b:mn></b:msub></b:mrow></b:math> are intensively studied on account of their unique electronic properties such as Ising superconductivity, found in multi- and monolayers, with upper critical fields beyond the Pauli limit. Even in bulk crystals, there are reports of multiband superconductivity and exotic states, such as the Fulde-Ferrell-Larkin-Ovchinnikov phase. In this work, we investigate the superconducting properties of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mn>2</c:mn><c:mi>H</c:mi><c:mtext>−</c:mtext><c:msub><c:mi>NbS</c:mi><c:mn>2</c:mn></c:msub></c:mrow></c:math> through a detailed high-field mapping of the phase diagram by means of magnetotransport and magnetostriction experiments. We compare the phase diagram between bulk crystals and a 6-nm-thick flake of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mn>2</d:mn><d:mi>H</d:mi><d:mtext>−</d:mtext><d:msub><d:mi>NbS</d:mi><d:mn>2</d:mn></d:msub></d:mrow></d:math> and find a drastically enhanced Maki parameter in the flake, signifying a change of the relevant pair-breaking mechanism from orbital to paramagnetic pair breaking, which we attribute to an effect of enhanced spin-orbit coupling. Published by the American Physical Society 2024