# Orbitally resolved superconductivity in real space: FeSe

## TL;DR

This paper introduces a novel low-temperature STM method to directly resolve orbital contributions to superconductivity in FeSe at atomic resolution, bypassing traditional scattering techniques and combining experimental data with theoretical calculations.

## Contribution

It presents a new approach using STM to identify orbital-specific superconducting gaps in FeSe without relying on surface scatterers or QPI measurements.

## Key findings

- Successfully resolved superconducting gaps within the unit cell.
- Identified the orbital character of each superconducting gap.
- Demonstrated the method's capability on defect-free crystals.

## Abstract

Multi-orbital superconductors combine unconventional pairing with complex band structures, where different orbitals in the bands contribute to a multitude of superconducting gaps. We here demonstrate a fresh approach using low-temperature scanning tunneling microscopy (LT-STM) to resolve the contributions of different orbitals to superconductivity. This approach is based on STM's capability to resolve the local density of states (LDOS) with a combined high energy and sub unit-cell resolution. This technique directly determines the orbitals on defect free crystals without the need for scatters on the surface and sophisticated quasi-particle interference (QPI) measurements. Taking bulk FeSe as an example, we directly resolve the superconducting gaps within the units cell using a 30 mK STM. In combination with density functional theory calculations, we are able to identify the orbital character of each gap.