US scientists discover material that switches quantum states on demand

US scientists led by Argonne National Laboratory have discovered a rare quantum material, KxNi4S2, that can switch between two distinct electronic states on demand. This nickel sulfide compound consists of nickel and sulfur layers sandwiched between potassium layers, with potassium content tunable from zero to one. By applying an electrical current, potassium ions can be reversibly removed or reinserted, causing the material’s structure to collapse or restore, thereby switching between two quantum states: Dirac cones and flat bands. In the Dirac state, electrons behave as nearly massless and move extremely fast, while in the flat-band state, electrons slow down and behave as heavier particles. This switching ability effectively allows the material to control electron speed and flow dynamically. The discovery is significant because such tunable quantum phases within a single material are rare and could revolutionize electronic device design. Instead of relying on multiple materials, devices could use this single material to adjust electronic behavior in real time, potentially enhancing performance,