Performance benchmarking of an ultra-low vibration laboratory to host a commercial millikelvin scanning tunnelling microscope.

Ultra-low temperature scanning tunnelling microscopy and spectroscopy (STM/STS) achieved by dilution refrigeration can provide unrivalled insight into the local electronic structure of quantum materials and atomic-scale quantum systems. Effective isolation from mechanical vibration and acoustic noise is critical in order to achieve ultimate spatial and energy resolution. Here, we report on the design and performance of an ultra-low vibration (ULV) laboratory hosting a customized but otherwise commercially available 40 mK STM. The design of the vibration isolation consists of a T-shaped concrete mass block (∼55t), suspended by actively controlled pneumatic springs, and placed on a foundation separated from the surrounding building in a 'room-within-a-room' design. Vibration levels achieved are meeting the VC-M vibration standard at >3 Hz, reached only in a limited number of laboratories worldwide. Measurement of the STM's junction noise confirms effective vibration isolation on par with custom built STMs in ULV laboratories. In this tailored low-vibration environment, the STM achieves an energy resolution of 43µeV (144 mK), promising for the investigation and control of quantum matter at atomic length scales.

Experimental study on sound transmission loss of plenum windows.

To investigate the noise reduction mechanism of plenum windows, the paper experimentally studied the influence of the air-gap spacing between two glass panes, the panel thickness, and the opening size on the sound transmission loss (TL). The results show that when the half wavelength of impinged sound is smaller than the air-gap spacing, the TL can be improved by the decrement of the opening sizes and the increment of the glass thickness but varies little with changes in air-gap spacing. When the half wavelength of impinged sound is larger, the modification of the three factors makes little impact on the TL.