  Atomtronics focuses on atom analogs of electronic materials, devices and
circuits. A strongly interacting ultracold Bose gas in a lattice potential is
analogous to electrons in solid-state crystalline media. As a consequence of
the band structure, cold atoms in a lattice can exhibit insulator or conductor
properties. P-type and N-type material analogs can be created by introducing
impurity sites into the lattice. Current through an atomtronic wire is
generated by connecting the wire to an atomtronic battery which maintains the
two contacts at different chemical potentials. The design of an atomtronic
diode with a strongly asymmetric current-voltage curve exploits the existence
of superfluid and insulating regimes in the phase diagram. The atomtronic
analog of a bipolar junction transistor exhibits large negative gain. Our
results provide the building blocks for more advanced atomtronic devices and
circuits such as amplifiers, oscillators and fundamental logic gates.
