Universal Linear Density of States for Tunneling into the Two-Dimensional Electron Gas in a Magnetic Field

We have developed a technique capable of measuring the tunneling current into both localized and conducting states in a 2D electron system. I- V characteristics for tunneling are obtained with no distortions arising from low 2D in-plane conductivity. In a perpendicular magnetic field, a pseudogap develops in the tunneling density of states at the Fermi energy. We resolve a linear energy dependence of this pseudogap at low excitations. The slopes of this linear gap are strongly field dependent. The data are suggestive of a new model of the gap in the presence of disorder and external screening.