Millikelvin scanning tunneling microscope at 20/22 T with a graphite enabled stick-slip approach and an energy resolution below 8$\mu$eV: Application to conductance quantization at 20 T in single atom point contacts of Al and Au

Abstract

We describe a scanning tunneling microscope (STM) that operates at magnetic fields up to 22 Tesla and temperatures down to 80 mK. We discuss the design of the STM head, with an improved coarse approach, the vibration isolation system, and efforts to improve the energy resolution using compact filters for multiple lines. We measure the superconducting gap and Josephson effect in Aluminum and show that we can resolve features in the density of states as small as 8\,$\mu$eV. We measure the quantization of conductance in atomic size contacts and make atomic resolution and density of states images in the layered material 2H-NbSe$_2$. The latter experiments are performed by continuously operating the STM at magnetic fields of 20 T in periods of several days without interruption.