Terahertz magneto-nanoscopy of encapsulated monolayer graphene

TL;DR

This paper uses terahertz near-field microscopy to explore how magnetic fields affect the nanoscale conductivity of encapsulated monolayer graphene at very low temperatures, revealing field-tunable cyclotron resonance.

Contribution

It demonstrates the application of s-SNOM to study magnetic-field-dependent terahertz responses in graphene at cryogenic temperatures, advancing nanoscale quantum material analysis.

Findings

Graphene exhibits near-perfect high-q reflector behavior with magnetic field influence.

Measurements match calculations of magneto-optical conductivity and cyclotron resonance.

Provides initial insights into temperature and magnetic effects on nanoscale terahertz transport.

Abstract

This study investigates the nanoscale conductivity of encapsulated monolayer graphene at temperatures down to 5 K and magnetic fields of up to 1 T. We use the scattering-type scanning near-field optical microscopy (s-SNOM) technique to probe magnetic-field-dependent responses from graphene close to charge neutrality in the terahertz spectral region. We observe the near-perfect high-$q$ reflector behavior of graphene but with subtle changes by the presence of magnetic fields. Measurements align with calculations of the magneto-optical conductivity and the near-field spectroscopic contrast that describes the field-tunable cyclotron resonance of Dirac fermions. Our result provides an initial step toward understanding temperature and magnetic-field effects on nanoscale terahertz transport in two-dimensional quantum materials.