Fig. 2: Interlayer charge dynamics in 2H-NbS2.
a Scanning electron microscope image of a 2H-NbS2 sample, structured with focused ion beam for accurate resistivity anisotropy measurements. False colouring is used: purple – crystal, beige – gold film. The scale bar in the bottom left is 20 µm long. The current sourcing (I) and voltage probing (V) electrodes are labelled. b Plots of the in-plane (ρab, blue) and out-of-plane (ρc, red) resistivities of 2H-NbS2 against temperature (T). The dashed red line stands for the out-of-plane resistivity of 2H-NbSe2, scaled by a factor of 2. Resistivity anisotropy of 2H-NbS2 is plotted in the inset. c Seebeck coefficients of 2H-NbS2 for the out-of-plane (Sc) and in-plane (Sab) directions as functions of temperature, measured on bulk single crystals (note that Sab is negative). The setup for measuring Sc is illustrated schematically. The crystal was approximately 1 mm long in the c axis direction (indicated in the drawing), and 2–3 mm long laterally. The value of Sc is the ratio of the voltage across the sample (Vs) and the thermal gradient across it, determined from the differential thermocouple voltage (VDTC). The sample sat between two copper plates, which homogenised temperature at its two faces and was electrically decoupled from the heatsink by a thin sapphire plate.
