These materials may exhibit an electric arc when a voltage larger than the breakdown voltage causes a charge to leap across them, but under normal conditions have an extremely high resistivity.
One class of these materials has special surface states protected by time-reversal symmetry, and are known as the "topological" type of these materials. These materials must have an even integer number of electrons per unit cell, which means that these materials have a perfectly filled valence band, above which there is a large band gap. These materials may exhibit an electric arc when a voltage larger than the breakdown voltage causes a charge to leap across them, but under normal conditions have an extremely high resistivity. For 10 points, identify these materials such as glass and rubber that block electrical current, in contrast to conductors.
One class of these materials has special surface states protected by time-reversal symmetry, and are known as the "topological" type of these materials.
electrical insulators