Origin of 'bad metal' downward curvature in UAs2 resistivity under pressure

Determine the physical mechanism responsible for the downward curvature of the temperature-dependent electrical resistance R(T) observed in UAs2 at low temperatures under pressures approximately 5–20 GPa, which the authors designate as 'bad metal' behavior.

Background

In constructing the temperature–pressure phase diagram for UAs2, the authors analyze normal-state transport by fitting R(T) to a power-law form and identify distinct regimes: Fermi-liquid (n ≈ 2), strange metal (n ≈ 1), and a region exhibiting a pronounced downward curvature in R(T) at low temperatures for intermediate pressures. They refer to this anomalous transport as 'bad metal' behavior.

Specifically, they report a strange downward curvature in R(T) in the low-temperature limit for pressures between about 5 and 20 GPa and explicitly state that its origin is unknown. Resolving this mechanism is important for understanding the evolution from antiferromagnetism to unconventional superconductivity and its relation to quantum criticality in uranium-based 5f-electron systems.

References

Note that a strange downward curvature of resistance versus temperature was observed in the pressure region from 5 to 20 GPa in the low temperature limit. We don’t know yet what is the reason for this downward shape in the low pressure region, thus we mark it as "bad metal" in Fig.4.

— Unconventional superconductivity emerging along with the strange-metal behavior in UAs2 under pressure  (2408.14334 - Li et al., 2024) in Section 3, T-P phase diagram of UAs2 (main text; near Figure 4)