trend such that by δ = 0.01, it is located clearly below the Dirac node (Fig. 2(e)) and intersects the hole-like bulk valence band. The systematic lowering of E$_{F}$ with increasing δ in Bi$_{2}$$_{−}$$_{δ}$Ca$_{δ}$Se$_{3}$ observed in early time ARPES measurements (Figs 2(i)-(k)), which reflect the electronic structure of the sample bulk, consistently explain the measured transport behavior. However, we observe that E$_{F}$ rises back up over time across all samples such that all spectra relax back to a δ = 0 like spectrum on a typical time scale of 18 hours (Fig. 2(l)). Such a slow upward shift of the surface Fermi level has been observed also in Bi$_{2}$Te$_{3}$ [17] and is due to a surface band bending effect commonly observed in most semiconductors (SI). Therefore, although bulk Ca doping succeeds in tuning E$_{F}$ between the bulk valence and conduction bands, it does not change the position of E$_{F}$ relative to the surface Dirac point in the ground state. Because the surface Dirac point in the ground state of most insulating Bi$_{1}$$_{.}$$_{9975}$Ca$_{0}$$_{.}$$_{0025}$Se$_{3}$ lies ∼ 0.3 eV below E$_{F}$ , its electronic structure is still not in the much desired topological transport regime. To bring the surface Dirac point level with E$_{F}$ in Bi$_{2}$$_{−}$$_{δ}$Ca$_{δ}$Se$_{3}$, we show that hole carriers can be systematically introduced into the surface by dosing with NO$_{2}$ molecules, which has been demonstrated in graphene [27, 28]. Figure 3 shows that with increasing surface hole donor concentration, the binding energy of the surface Dirac point rises monotonically towards E$_{F}$ . Starting from E$_{B}$ ∼ -0.3 eV at a 0 Langmuir (L) dose, it rises to -0.15 eV at 0.1 L where the surface bent CBM has completely disappeared, and finally to the charge neutrality point ( E$_{B}$ = 0 eV) at 2 L. No further changes of the chemical potential are observed with higher dosages. To quantify the surface carrier density ( n ) dependence on surface hole donor concentration, we mapped the surface state FS in Figures 3(a)-(c) and performed an electron count based on FS area n = A$_{F S}$ / A$_{BZ}$ , where A$_{F S}$ is the area of the FS and A$_{BZ}$ is the area of the surface Brillouin zone. We find that 0.1 L of NO$_{2}$ removes approximately 0.0066 electrons per surface unit cell of Bi$_{2}$$_{−}$$_{δ}$Ca$_{δ}$Se$_{3}$ (111), and an excess of 2 L reduces the FS to a single point within our experimental resolution, which has an additional 0.005 electrons per unit cell removed. Because surface doping does not affect the carrier density in the bulk (which thus remains insulating), the energy of the Dirac point is lifted above the bulk VBM; a new time independent electronic ground state is realized that lies in the topological transport regime with E$_{F}$ intersecting the Dirac node. In order to investigate the thermal stability of this nodal Dirac ground state (Fig. 4(e)), temperature dependent ARPES scans were collected on Bi$_{2}$$_{−}$$_{δ}$Ca$_{δ}$Se$_{3}$ samples that were first 7