Pressure-Induced Superconducting Phase in the Charge-Density-Wave Compound Terbium Tritelluride

A series of high-pressure electrical resistivity measurements on single crystals of ${\mathrm{TbTe}}_3$ reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge-density-wave order. The onset of superconductivity reaches a maximum of almost 4 K (onset) near $\sim 12.4\mathrm{GPa}$.

Figure 1

Specific heat $C$ versus temperature $T$ for ${\mathrm{TbTe}}_3$ at ambient pressure and fields up to 5 T. For clarity, the curves have been offset vertically by a constant amount indicated in parentheses near the right side of the curves. Three distinct peaks, indicated by arrows, are visible near the Néel temperature at 6 K. Inset: The field dependence of the specific heat anomalies. The dashed line fits are described in the text.

Figure 2

Electrical resistivity measured in the $ac$ plane of ${\mathrm{TbTe}}_3$ under nearly hydrostatic pressures to 2.3 GPa. The curves have been offset vertically for clarity. The pressure and magnitude of the offset are indicated in parentheses at the right of the curves. The onset of the CDW is clearly seen to shift downward with pressure. At and above 1.2 GPa, a second feature in the resistivity is clearly visible as a minimum in the slope $d\rho /dT$ (inset). At 2.3 GPa, the two transitions $T_{\mathrm{CDW}}$ and $T^{*}$ appear to be nearly coincident.

Figure 3

Electrical resistivity measured in the $ac$ plane of ${\mathrm{TbTe}}_3$ at various pressures. The upper panel shows data from the piston-cylinder cell and first Bridgman anvil cell experiment, while the lower panel shows data taken from the second Bridgman anvil cell experiment. At several pressures, the resistance becomes negligible below the transition confirming SC. Upper inset: Resistivity versus temperature in the vicinity of $T_N$ at selected pressures. The dashed and solid black lines in the inset indicate the value of $T_N$ at 0.1 GPa. Lower inset: Relative change in the 6 K resistance, taken from the second Bridgman anvil cell experiment.

Figure 4

Pressure dependence of the transition temperatures of the phases observed in ${\mathrm{TbTe}}_3$. The value of $T_c$ is given by the transition midpoint, and the vertical error bars are determined by the 10%–90% width of the transition (the 10% value has been estimated via extrapolation where necessary). The point labeled “H” is from the hydrostatic cell run. The numbers indicate the order of measurement for the first Bridgman anvil cell run. Open squares are from the first Bridgman anvil cell run.