ETH-monotonicity in two-dimensional systems

We study a recently discovered property of many-body quantum chaotic systems called ETH-monotonicity in two-dimensional systems. Our new results further support ETH-monotonicity in these higher dimensional systems. We show that the flattening rate of the $f$-function is directly proportional to the number of degrees of freedom in the system, so as $L^2$ where $L$ is the linear size of the system, and in general, expected to be $L^d$ where $d$ is the spatial dimension of the system. We also show that the flattening rate is directly proportional to the particle (or hole) number for systems of same spatial size.