Novel transport properties of elemental superconductors under pressure

Several novel transport phenomena have emerged in the superconducting systems, including the intermediate anomalous metallic state (AMS) in the superconductor-insulator transition at ultralow temperatures and the metal-bosonic insulator-superconductor transition (MIST) near the critical temperature (T_c). These types of behavior, primarily observed in disordered or chemically doped low-dimensional systems, raise intriguing questions about their universality and the underlying physics.

In recent work, we present experimental evidence for a 3D AMS in highly compressed titanium, which shows superconductivity with a T_c of 25.1 K. At strong magnetic fields, we observed AMS characteristics, including low-temperature saturation resistance and giant positive magnetoresistance. This discovery offers a fresh platform to explore the long-standing enigmatic physics of AMS. Moreover, we found a magnetic field-induced MIST in highly compressed sulfur, marked by a resistance peak prior to superconductivity. Notably, it's the first instance of the concurrent observation of a prominent resistance peak as a function of temperature, magnetic field, and current in a superconductor. The findings on compressed sulfur, a well-established elemental superconductor, suggest the possibility of unveiling diverse electronic and transport phenomena in putatively simple systems and open avenues for further delving into the essence of anomalous transport mechanisms in condensed matter.