Figure 4
(a) Meissner force curves from the \(\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2\) single crystal at 0.5 K (blue solid line) and the reference sample (Nb, black solid line) to determine in-plane London penetration depth \(\lambda _{\text {L}}\). Using the comparative method (see the text), one can extract the absolute value of \(\lambda _{\text {L}}\). The addition of the shifted distance of 700 nm to the black solid line (red dashed line) leads to \(\lambda _{\text {L}}(0.5 \;\text {K}) = \lambda _{\text {L,Nb}}(0.5\; \text {K})+z\) = 110 nm + 700 nm = 810 nm. Inset : MFM image obtained at T = 0.5 K. (b) Temperature dependence of the \(\lambda _{\text {L}}\). Below \(\frac{1}{3}T_c\), \(\lambda _{\text {L}}(T)\) is fitted to both the single-band BCS formula (green dashed line) and the power-law (\(AT^n\), red dashed line). The former fails to reproduce the data while the latter fits better the data with the exponent n about 2.66, constituting compelling evidence on nodeless, multiband nature of the superconducting gap.
