I mean, if you want to talk about our actual tech, it's bound by lithography of silicon chips, which are largely n^2, on printed circuit boards, which are n^2, on the surface area of the earth, which is n^2.

This has been observed since at least 2014: https://www.ilikebigbits.com/2014_04_21_myth_of_ram_1/3_fit....

Pretty much every physical metric pegs memory access as O(n^1/2).