Spontaneous and explicit parity-time-symmetry breaking in drift wave instabilities of magnetized plasmas

The drift wave in magnetized plasmas typically depends on 7 or 8 dimensionless parameters, resulting in many different paths to instabilities. We introduce a method of Parity-Time (PT)-symmetry analysis to study the high dimensional, complex parameter space of drift wave instabilities. The main results include:  (1) It is shown that spontaneous PT-symmetry breaking leads to the Ion Temperature Gradient (ITG) instability, whereas the collisional instability and the universal mode are the results of explicit PT-symmetry breaking. (2) Drift wave instabilities by spontaneous PT-symmetry breaking have instability thresholds due to topological constraints on the spectrum, but those by explicit PT-symmetry breaking do not. (3) When the ITG mode is stabilized, the relative phase between density perturbation and ion flow in the inhomogeneous direction needs to be locked at π/2, which can be used as a measurable criterion in experiments. (4) A new unstable drift wave induced by finite collisionality is identified. (5) It is also found that gradients of ion temperature and density can destabilize the ion cyclotron waves when PT symmetry is explicitly broken by a finite collisionality.