A reversible transition in liquid Bi under pressure.

Area of Science:

• Materials Science
• Condensed Matter Physics
• High-Pressure Geophysics

Background:

• Understanding the behavior of materials under extreme conditions is crucial for various scientific fields.
• Bismuth (Bi) exhibits complex phase transitions, making it a key subject for high-pressure research.
• Previous studies on Bi have explored its solid-state properties, but its liquid phase behavior under pressure remains less understood.

Purpose of the Study:

• To investigate the electrical resistance of solid and liquid bismuth (Bi) at high pressures and temperatures.
• To identify and characterize any novel transitions occurring in molten Bi beyond its melting point.
• To map the pressure-temperature phase diagram of Bi, focusing on the newly observed liquid-phase transition.

Main Methods:

• Utilized a novel experimental design with a "Paris-Edinburgh" toroid large volume press for high-sensitivity electrical resistance measurements.
• Performed measurements on solid and liquid Bi across a range of high pressures and temperatures.
• Conducted both heating and cooling cycles to assess the reversibility of observed phenomena.

Main Results:

• Observed an anomalous, sharp decrease in electrical resistivity with increasing temperature at constant pressures in the liquid phase of Bi.
• Confirmed the reversibility of this transition across various pressures and during both heating and cooling cycles.
• Determined a distinct "phase-line" for this novel transition on the Bi pressure-temperature phase diagram, which terminates at the melting curve.

Conclusions:

• The observed anomalous resistivity decrease indicates a possible novel phase transition in molten bismuth (Bi) under high pressure.
• This transition is reversible and can be mapped onto the Bi pressure-temperature phase diagram.
• The findings contribute to a deeper understanding of material behavior under extreme conditions and the fundamental physics of liquid metals.