Cryogenic Magneto-Terahertz Scanning Near-field Optical Microscope (cm-SNOM)

TL;DR

This paper introduces a novel cryogenic magneto-THz scanning near-field optical microscope capable of operating at ultra-low temperatures and high magnetic fields, enabling advanced nanoscopic studies of quantum materials.

Contribution

The development of the first cryogenic magneto-THz nano-spectroscopy platform combining high magnetic fields, cryogenic temperatures, and near-field optical imaging.

Findings

First cryogenic magneto-THz nano-spectroscopy at 1.8 K and 5 T

Demonstrated imaging of superconducting and topological materials

Enabled studies of quantum materials under extreme conditions

Abstract

We have developed a versatile near-field microscopy platform that can operate at high magnetic fields and below liquid-helium temperatures. We use this platform to demonstrate an extreme terahertz (THz) nanoscope operation and to obtain the first cryogenic magneto-THz time-domain nano-spectroscopy/imaging at temperatures as low as 1.8 K and magnetic fields of up to 5 T simultaneously. Our cryogenic magneto-THz scanning near-field optical microscopy, or cm-SNOM, instrument comprises three main equipment: i) a 5 T split pair magnetic cryostat with a custom made insert for mounting SNOM inside; ii) an atomic force microscope (AFM) unit that accepts ultrafast THz excitation and iii) a MHz repetition rate, femtosecond laser amplifier for high-field THz pulse generation and sensitive detection. We apply the cm-SNOM to obtain proof of principle measurements of superconducting and topological materials. The new capabilities demonstrated break grounds for studying quantum materials that requires extreme environment of cryogenic operation and applied magnetic fields simultaneously in nanometer space, femtosecond time, and terahertz energy scales.