Typical height of the (2+1)-D Solid-on-Solid surface with pinning above a wall in the delocalized phase

We study the typical height of the (2+1)-dimensional solid-on-solid surface with pinning interacting with an impenetrable wall in the delocalization phase. More precisely, let $\Lambda_N$ be a $N \times N$ box of $\mathbb{Z}^2$, and we consider a nonnegative integer-valued field $(\phi(x))_{x \in \Lambda_N}$ with zero boundary conditions (i.e. $\phi|_{\Lambda_N^{\complement}}=0$) associated with the energy functional $$\mathcal{V} (\phi)= \beta \sum_{x \sim y} \vert \phi(x)-\phi(y) \vert- \sum_{x} h \mathbf{1}_{\{ \phi(x)=0\}},$$ where $\beta>0$ is the inverse temperature and $h\ge 0$ is the pinning parameter. Lacoin has shown that for sufficiently large $\beta$, there is a phase transition between delocalization and localization at the critical point $$h_w(\beta)= \log \left( \frac{e^{4 \beta}}{e^{4 \beta}-1}\right).$$ In this paper we show that for $\beta\ge 1$ and $h \in (0, h_w)$, the values of $\phi$ concentrate at the height $H= \lfloor (4 \beta)^{-1} \log N \rfloor$ with constant order fluctuations. Moreover, at criticality $h=h_w$, we provide evidence for the conjectured typical height $H_w= \lfloor (6 \beta)^{-1} \log N \rfloor$.