  In this supporting material for the main paper (the preceding submission), we
show, in addition to the related information for the experiments, additional
discussion that cannot fit in the main paper (due to the space constraint). It
includes further discussion about our experimental observations, wider
implications of our main findings with various reported candidates for the
pseudogap order, and a simple mean-field argument that favors interpretations
based on a finite-Q order (density wave) for the pseudogap seen by ARPES
(whether "the pseudogap order" is a single order or contains multiple
ingredients, is an independent, open issue). We also include a detailed
simulation section, in which we model different candidates (various density
wave/nematic order) for the pseudogap order in simple forms using a mean-field
approach, and discuss their partial success as well as limitations in
describing the experimental observations. These simulations are based on a
tight-binding model with parameters fitted globally (and reasonably well) to
the experimental band dispersions (by tracking the maximum of the energy
distribution curve), which could be useful for further theoretical explorations
on this issue.
