An ultra-high vacuum scanning tunneling microscope operating at sub-Kelvin temperatures and high magnetic fields for spin-resolved measurements

TL;DR

This paper describes the development of an ultra-high vacuum, sub-Kelvin temperature scanning tunneling microscope capable of high magnetic field operation, enabling advanced spin-resolved measurements with high spatial and energy resolution.

Contribution

The paper introduces a novel ultra-low temperature STM design that integrates UHV sample handling and spin-resolved measurement capabilities at sub-Kelvin temperatures.

Findings

Successful operation at 300 mK with 80-hour stability

High spatial and energy resolution demonstrated

Effective spin-resolved measurements on superconducting and metallic samples

Abstract

We present the construction and performance of an ultra-low temperature scanning tunneling microscope (STM), working in ultra-high vacuum conditions (UHV) and in high magnetic fields up to 9 T. The cryogenic environment of the STM is generated by a single shot $^3$He magnet cryostat in combination with a $^4$He dewar system. At base temperature (300~mK), the cryostat has an operation time of approximately 80 hours. The special design of the microscope allows the transfer of the STM head from the cryostat to a UHV-chamber system, where samples and STM-tips can be easily exchanged. The UHV chambers are equipped with specific surface science treatment tools for the functionalization of samples and tips, including high-temperature treatments and thin film deposition. This, particularly, enables spin-resolved tunneling measurements. We present test measurements using well known samples and tips based on superconductor and metallic materials such as LiFeAs, Nb, Fe and W, respectively. The measurements demonstrate the outstanding performance of the STM with high spatial and energy resolution as well as the spin-resolved capability.