Experimental observation of the dual behavior of ${\cal PT}$-symmetric scattering

TL;DR

This paper experimentally demonstrates the dual nature of ${ m PT}$-symmetric scattering in coupled circuits, showing amplification, absorption, and unidirectional transparency due to non-reciprocal scattering properties.

Contribution

It provides the first experimental observation of ${ m PT}$-symmetric scattering behaviors, including dual amplification/absorption and unidirectional transparency, in coupled circuit systems.

Findings

${ m PT}$-symmetric circuits act as amplifiers or absorbers depending on orientation.

The system exhibits unidirectional transparency at specific frequencies.

Non-reciprocal scattering relations govern the observed behaviors.

Abstract

We investigate experimentally parity-time (${\cal PT}$) symmetric scattering using $LRC$ circuits in an inductively coupled ${\cal PT}$- symmetric pair connected to transmission line leads. In the single-lead case, the ${\cal PT}$-symmetric circuit acts as a simple dual device - an amplifier or an absorber depending on the orientation of the lead. When a second lead is attached, the system exhibits unidirectional transparency for some characteristic frequencies. This non-reciprocal behavior is a consequence of generalized (non-unitary) conservation relations satisfied by the scattering matrix.