# Precision Measurement of the Optical Conductivity of Atomically Thin Crystals via Photonic Spin Hall Effect

## TL;DR

This paper introduces a highly sensitive method using the photonic spin Hall effect combined with weak-value amplification to precisely measure the optical conductivity of atomically thin crystals like graphene, achieving high resolution and revealing layer-dependent conductivity.

## Contribution

The study demonstrates a novel measurement technique that leverages the photonic spin Hall effect and weak-value amplification for accurate optical conductivity detection in atomically thin materials.

## Key findings

- Optical conductivity of monolayer graphene measured as (0.993±0.005)σ₀.
- High measurement resolution of 1.5×10⁻⁸ Ω⁻¹ achieved.
- Conductivity increases linearly with layer number in few-layer graphene.

## Abstract

How to measure the optical conductivity of atomically thin crystals is an important but challenging issue due to the weak light-matter interaction at the atomic scale. Photonic spin Hall effect, as a fundamental physical effect in light-matter interaction, is extremely sensitive to the optical conductivity of atomically thin crystals. Here, we report a precision measurement of the optical conductivity of graphene, where the photonic spin Hall effect acts as a measurement pointer. By incorporating with the weak-value amplification technique, the optical conductivity of monolayer graphene taken as a universal constant of $(0.993\pm0.005)\sigma_0$ is detected, and a high measuring resolution with $1.5\times10^{-8}\Omega^{-1}$ is obtained. For few-layer graphene without twist, we find that the conductivities increase linearly with layer number. Our idea could provide an important measurement technique for probing other parameters of atomically thin crystals, such as magneto-optical constant, circular dichroism, and optical nonlinear coefficient.