Local density of states above a disk -- geometrical vs. thermal boundary conditions

TL;DR

This paper analytically investigates the local density of states above a metal disk considering thermal sources and boundary conditions, comparing analytical, cutoff, and numerical methods to understand near-field effects in microscopy.

Contribution

It introduces a wavevector cutoff method for LDOS approximation and compares thermal versus geometrical boundary conditions in near-field scenarios.

Findings

Analytical and numerical LDOS results show good agreement.

Thermal and geometrical boundary conditions exhibit distinct effects on LDOS.

Wavevector cutoff effectively approximates thermal contributions to LDOS.

Abstract

We analytically calculate the contribution to the local density of states due to thermal sources in a disk-like patch within the framework of fluctuational electrodynamics. We further introduce a wavevector cutoff method to approximate this contribution. We compare the results obtained with the source and cutoff method with the numerical exact LDOS above a metal disk attained by SCUFF-EM calculations. By this comparison we highlight the difference and resemblance of thermal and geometrical boundary conditions which are both relevant for near-field scanning microscope measurements. Finally, we give an outlook to general lateral temperature profiles and compare it with surface profiles.