When you flip a switch, the light doesn't come on immediately — electrons in the wires need time to 'get going' and move together. In ordinary metals and semiconductors, current builds up gradually, like water in a hose when you first open the tap. But in materials called quantum-geometric semimetals, it's different: apply a field, and electrons are off like a shot, as if at the command 'March!' without a running start. The secret lies in how their energy bands are arranged: at the points where bands touch, electrons of different 'kinds' are strongly mixed, and the slightest external nudge instantly turns this mixing into a directed flow.
The authors showed that this instantaneous response is not just a theoretical curiosity. They simulated how a semimetallic film behaves under a series of short laser pulses, and the current dutifully turned on and off, following the light almost without delay. For comparison, they took graphene, copper, and silicon: in all cases, current took longer to 'get going,' and its switching on and off was smeared out. In quantum-geometric semimetals, the signal front is as sharp as a drumstick strike.
Among the candidates for such a material are bilayer graphene twisted at a specific angle, cyclic graphene, as well as single-atom layers of bismuth and the compound V3F8. First-principles calculations confirm that the effect should be observable at voltages comparable to those used in modern chips. If this can be transferred from laboratory laser setups to mass-produced transistors, electronics could switch orders of magnitude faster while barely heating up.
So the familiar delay between pressing a button and the device responding could disappear — at least inside the device itself. Instead of a gradual build-up, electrons would spring into action like sprinters hearing the starting pistol.
In bismuth, which alchemists already used, electrons behave as if they have no mass, and this helps current appear almost instantly.
In Peter Watts' novel 'Blindsight,' alien ships react to threats without the slightest delay — similar to how circuits made of such semimetals might work.