Extreme orbital <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>a</mml:mi><mml:mi>b</mml:mi></mml:mrow></mml:math>-plane upper critical fields far beyond the Pauli limit in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>4</mml:mn><mml:msub><mml:mi>H</mml:mi><mml:mi>b</mml:mi></mml:msub><mml:mtext>−</mml:mtext><mml:mi>Ta</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="normal">S</mml:mi><mml:mo>,</mml:mo><mml:mi>Se</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> bulk crystals
Fanyu Meng, Yang Fu, Senyang Pan, Shangjie Tian, Shaohua Yan, Zhengyu Li, Shouguo Wang, Jinglei Zhang, Hechang Lei
Abstract
Transition metal disulfides $4{H}_{b}$-Ta(S, ${\mathrm{Se})}_{2}$ with natural heterostructure of $1T$- and $1H$-Ta(S, ${\mathrm{Se})}_{2}$ layers have became the focus of correlated materials their unique combinations of Mott physics and possible topological superconductivity. In this work, we study the upper critical fields ${\ensuremath{\mu}}_{0}{H}_{c2}$ of $4{H}_{b}\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ and $4{H}_{b}\text{\ensuremath{-}}{\mathrm{TaS}}_{1.99}{\mathrm{Se}}_{0.01}$ single crystals systematically. Transport measurements up to 35 T show that both of $ab$-plane and $c$-axis upper critical fields (${\ensuremath{\mu}}_{0}{H}_{c2,ab}$ and ${\ensuremath{\mu}}_{0}{H}_{c2,c}$) for $4{H}_{b}\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ and $4{H}_{b}\text{\ensuremath{-}}{\mathrm{TaS}}_{1.99}{\mathrm{Se}}_{0.01}$ exhibit a linear temperature dependent behavior down to 0.3 K, suggesting the three-dimensional superconductivity with dominant orbital depairing mechanism in bulk $4{H}_{b}$-Ta(S, ${\mathrm{Se})}_{2}$. However, the zero-temperature ${\ensuremath{\mu}}_{0}{H}_{c2,ab}$(0) for both crystals are far beyond the Pauli paramagnetic limit ${\ensuremath{\mu}}_{0}H{}_{\mathrm{P}}$. It could be explained by the effects of spin-momentum locking in $1H$-Ta(S, ${\mathrm{Se})}_{2}$ layers with local inversion symmetry broken and the relatively weak intersublattice interaction between $1H$ layers due to the existence of $1T$ layers.