Matter waves, single-mode excitations of the matter-wave field, and the atomtronic transistor oscillator

A self-consistent theoretical treatment of a triple-well atomtronic transistor circuit reveals the mechanism of gain, conditions of oscillation, and properties of the subsequent coherent matter waves emitted by the circuit. A Bose-condensed reservoir of atoms in a large source well provides a chemical potential that drives circuit dynamics. The theory is based on the ansatz that a condensate arises in the transistor gate well as a displaced ground state, that is, one that undergoes dipole oscillation in the well. That gate atoms remain condensed and oscillating is shown to be a consequence of the cooling induced by the emission of a matter wave into the vacuum. Key circuit parameters such as the transistor transconductance and output current are derived by transitioning to a classical equivalent circuit model. Voltage-like and current-like matter-wave circuit wave fields are introduced in analogy with microwave circuits, as well as an impedance relationship between the two. This leads to a notion of a classically coherent matter wave that is the dual of a coherent electromagnetic wave and which is distinct from a de Broglie matter wave associated with cold atoms. Subjecting the emitted atom flux to an atomic potential that will reduce the de Broglie wavelength, for example, will increase the classical matter-wave wavelength. Quantization of the classical matter-wave fields leads to the dual of the photon that is identified not as an atom but as something else, which is here dubbed a ``matteron.''