Observation of slowly decaying eigenmodes without exceptional points in Floquet, dissipative, synthetic circuits

TL;DR

This paper experimentally demonstrates the emergence and disappearance of slowly decaying eigenmodes in a dissipative Floquet system without the occurrence of exceptional points, challenging conventional understanding.

Contribution

It provides the first experimental observation of such transitions in a dissipative Floquet system without exceptional points, using synthetic electronic circuits.

Findings

Slowly decaying eigenmodes emerge at very low dissipation in weak coupling.

Multiple emergence and disappearance events occur with moderate Floquet coupling.

Transitions are driven by avoided-level-crossing phenomena in dissipative systems.

Abstract

We report the first experimental observation of multiple transitions showing the emergence and disappearance of slowly decaying eigenmodes in a dissipative, Floquet electronic system with synthetic components. Conventional wisdom has it that such transitions occur at exceptional points, and avoided-level-crossing driven phenomena in purely dissipative systems are formerly unexplored. Remarkably, in our system, the slowly decaying eigenmodes emerge without exceptional points. Our experimental setup makes use of an LC oscillator inductively coupled to an RLC oscillator, where the time-periodic (Floquet) inductive coupling and resistive-heating losses can be independently controlled by means of external voltage signals. With a Floquet dissipation, we observe that slowly-decaying eigenmodes emerge at vanishingly small dissipation strength in the weak coupling limit. With a moderate, Floquet coupling, multiple instances of their emergence and disappearance are observed. With an asymmetric dimer model, we show that these transitions, driven by avoided-level-crossing in purely dissipative systems, are generically present in both static and Floquet domains.