Two-dimensional multigap superconductivity in bulk $2H\text{−}\mathrm{TaSeS}$

Superconducting transition metal dichalcogenides have emerged as a platform for hosting novel and nontrivial physical phenomena. We report a detailed investigation of superconducting and transport properties on $2H\text{−}\mathrm{TaSeS}$ single crystals. It suggests that TaSeS is a multigap anisotropic superconductor with the upper critical field, breaking the Pauli limiting field in both in-plane and out-of-plane directions. The angle dependence of the upper critical field suggests the two-dimensional superconducting nature in bulk $2H\text{−}\mathrm{TaSeS}$.

Figure 1

(a) Shows the microscopic image of the single crystal and the Laue image in the inset. (b) Single crystal powder x-ray diffraction pattern indicates crystal oriented along the $\left[00l\right]$ plane. (c) Refinement of powder sample for determining lattice parameters. (d) Side view of $2H\text{−}\mathrm{TaSeS}$ unit cell.

Figure 2

(a) Zero resistivity drop happens at 3.905(5) K, and the inset shows the resistivity data above the superconducting transition temperature is fitted by the BG model. (b) Magnetization data was collected in ZFCW-FCC mode that shows the superconducting transition temperature at 3.90(1) K at 1 mT applied field.

Figure 3

(a) Low field variation of magnetization data in two different directions. (b) Lower critical field variation with temperature is well fitted with GL equations and gives values 4.3(2) and 2.1(1) mT for $H\perp c$ and $H\parallel c$ directions.

Figure 4

(a) and (b) Shows resistivity variation with temperature for $H\perp c$ and $H\parallel c$, respectively. (c) The two-gap fitting of the upper critical field from resistivity data for perpendicular and parallel directions and the black dashed line shows the Pauli limit of the upper critical field, i.e., $H_{c2}^P=1.86T_c=7.25$ T.

Figure 5

(a) The angle dependence resistivity variation indicates anisotropy in the system. (b) The angle dependence upper critical field from resistivity measurement 2.5 K fitted with the 3D GL model and the 2D Tinkham model.

Figure 6

(a) Low-temperature electronic contribution of specific data is better fitted with a two-gap comparative single-gap model. (b) The Sommerfeld coefficient was calculated from a field-dependent specific heat curve. The inset shows $\gamma$ depends on the square root of $H$.

Figure 7

The plot of the superconducting transition temperature versus the Fermi temperature for different superconducting families. In between, two solid blue lines show the unconventional band of superconductors. TaSeS lies close to the unconventional band.