  The Mott insulator is the quintessential strongly correlated electronic
state. We obtain complete insight into the physics of the two-dimensional Mott
insulator by extending the slave-fermion (holon-doublon) description to finite
temperatures. We first benchmark its predictions against state-of-the-art
quantum Monte Carlo simulations, demonstrating quantitative agreement.
Qualitatively, the short-ranged spin fluctuations both induce holon-doublon
bound states and renormalize the charge sector to form the Hubbard bands. The
Mott gap is understood as the charge gap renormalized downwards by these spin
fluctuations. As temperature increases, the Mott gap closes before the charge
gap, causing a pseudogap regime to appear naturally during the melting of the
Mott insulator.
