Fig. 4: Cryogenic reversible in situ direct-writing logic circuits.

a Schematic of light exposure on the sample surface with a hall bar patterned mask. The left side is shielded, and the right side forms a Hall bar pattern. b Modulation of the C-2DEG interface state. A 210 V back-gate pulse (1 ms) induces an insulating state, which transitions to a persistent conductive state after exposure to infrared (900 nm, 1.2 s) or ultraviolet light (300 nm, 1.2 s). c Hall resistance as a function of the external magnetic field measured in darkness following Hall bar pattern exposure. d Resistance of the insulating C-2DEG interface as a function of wavelength. Red and blue curves represent measurements for decreasing (1100–200 nm) and increasing (200–1100 nm) wavelengths, respectively. e Light flux (blue) and thermocouple temperature (red) versus wavelength (290–1100 nm). Temperature closely tracks light flux, suggesting thermal effects. f Source-drain current response in shielded and exposed regions. Ultraviolet light causes a localized non-volatile transition in the exposed region, while infrared light induces a gradual conductive transition in shielded areas due to thermal effects. g Conceptual illustration of ultraviolet laser direct-writing for creating conductive pathways. Schematic representations of serial (h) and parallel (i) logic circuit switching between cryogenic devices using “optical pencil” and “electric eraser” technology.