Non-Hermitian Casimir effect of magnons

Nakata, Koki   

Recently, there has been a growing interest in non-Hermitian quantum mechanics. However, the non-Hermitian extension of the Casimir effect and the application to spintronics remain missing ingredients. Here we fill this gap. By developing a magnonic analog of the Casimir effect into non-Hermitian systems, we show that this non-Hermitian Casimir effect of magnons is enhanced as the Gilbert damping constant (i.e., the energy dissipation rate) increases. When the damping constant exceeds a critical value, the non-Hermitian Casimir effect of magnons exhibits an oscillating behavior, including a beating one, as a function of the film thickness and is characterized by the exceptional point. Our result suggests that energy dissipation serves as a key ingredient of Casimir engineering.