Abstract

Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. Using near-field optical and photocurrent nanoscopy, the authors probe real-space variations of the optical and photothermal dynamics of monolayer graphene encapsulated in hexagonal boron nitride under high magnetic field. Near the charge neutrality point, strong optical and photothermal signals are observed from resonant inter-Landau-level magnetoexciton excitations between the 0th and ±1st Landau levels, which weaken with increasing doping due to Pauli blocking. At full integer Landau-level filling, photothermal signals reappear across the sample over a ~10-micrometer scale, indicating long cooling lengths and nonlocal photothermal heating through the insulating bulk.

Abstract

Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. Using near-field optical and photocurrent nanoscopy, the authors probe real-space variations of the optical and photothermal dynamics of monolayer graphene encapsulated in hexagonal boron nitride under high magnetic field. Near the charge neutrality point, strong optical and photothermal signals are observed from resonant inter-Landau-level magnetoexciton excitations between the 0th and ±1st Landau levels, which weaken with increasing doping due to Pauli blocking. At full integer Landau-level filling, photothermal signals reappear across the sample over a ~10-micrometer scale, indicating long cooling lengths and nonlocal photothermal heating through the insulating bulk.

Abstract

Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. Using near-field optical and photocurrent nanoscopy, the authors probe real-space variations of the optical and photothermal dynamics of monolayer graphene encapsulated in hexagonal boron nitride under high magnetic field. Near the charge neutrality point, strong optical and photothermal signals are observed from resonant inter-Landau-level magnetoexciton excitations between the 0th and ±1st Landau levels, which weaken with increasing doping due to Pauli blocking. At full integer Landau-level filling, photothermal signals reappear across the sample over a ~10-micrometer scale, indicating long cooling lengths and nonlocal photothermal heating through the insulating bulk.

Abstract

Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. Using near-field optical and photocurrent nanoscopy, the authors probe real-space variations of the optical and photothermal dynamics of monolayer graphene encapsulated in hexagonal boron nitride under high magnetic field. Near the charge neutrality point, strong optical and photothermal signals are observed from resonant inter-Landau-level magnetoexciton excitations between the 0th and ±1st Landau levels, which weaken with increasing doping due to Pauli blocking. At full integer Landau-level filling, photothermal signals reappear across the sample over a ~10-micrometer scale, indicating long cooling lengths and nonlocal photothermal heating through the insulating bulk.