Universal Dynamic Conductivity and Quantized Visible Opacity of Suspended Graphene

TL;DR

This paper demonstrates that suspended graphene's optical transparency and dynamic conductivity are universal, governed by fundamental constants, resulting in a quantized visible opacity despite its atomic thinness.

Contribution

It reveals that graphene's optical transparency and conductivity are universal, directly linked to the fine structure constant, highlighting a fundamental quantum property of this material.

Findings

Graphene absorbs approximately 2.3% of incident white light.

The dynamic conductivity of graphene is universally G = e^2/4h_bar.

Optical transparency is defined by the fine structure constant.

Abstract

We show that the optical transparency of suspended graphene is defined by the fine structure constant, alpha, the parameter that describes coupling between light and relativistic electrons and is traditionally associated with quantum electrodynamics rather than condensed matter physics. Despite being only one atom thick, graphene is found to absorb a significant (pi times alpha=2.3%) fraction of incident white light, which is a consequence of graphene's unique electronic structure. This value translates into universal dynamic conductivity G =e^2/4h_bar within a few percent accuracy.