A Fully-Passive, Quasi-Zero Stiffness Vibrational Isolator for Cryogen-Free Scanning Probe Microscopy

We demonstrate a novel, fully-passive vibration damping system designed to isolate a scanning tunneling microscope (STM) from the low-frequency noise introduced by a cryogen-free refrigerator pump. The design uses thin flexures to create an operating region of quasi-zero stiffness (QZS), effectively lowering the resonance frequency of the isolator into the sub-Hertz range and achieving < 1pm vibrational noise levels at the pump resonance frequency. The system is robust against cryogenic temperatures, and is compact enough to fit inside a dilution refrigerator, facilitating cryogen-free, low-temperature scanning probe microscopy (SPM).