35 T water-cooled magnet scanning tunneling microscope for in-plane magnetic field measurement

Manipulating the direction of the magnetic field can induce various intriguing physical phenomena, such as the regulation of nematic phase and disappearance of the charge density wave. Conventional superconducting magnet-based scanning tunneling microscopes (STMs) operate with a perpendicular magnetic field direction to the sample surface, limiting their ability to investigate anisotropy of materials. Some STMs are integrated into vector magnets to achieve in-plane magnetic field conditions; however, these setups typically offer a maximum lateral magnetic field strength of less than 5 T, which is far below the critical magnetic field required for many materials. To explore the anisotropy of materials under in-plane magnetic fields exceeding 20 T, a new STM with small lateral tip-sample junction, which is capable of working in huge vibrational water-cooled magnets, is required. This paper presents an innovative design of such a small lateral size featured STM that is capable of operating under 35 T in-plane magnetic field conditions. The proposed STM utilizes an improved spider drive to drive the tip move in oblique upward direction, with the component of tip motion on the lateral direction being one-fifth of the vertical direction. With the novel design, the lateral size of the STM head is minimized to as small as 15 mm. The high rigidity of an independent scanner is proved by the high eigenfrequencies obtained through finite element analysis. The excellent imaging ability of our new STM are demonstrated by the high-quality atomic images of graphite and NbSe2 acquired under in-plane magnetic fields ranging from 0 to 35 T, illustrating the new STM's high immunity to the magnetic field conditions. As far as known, this is the first STM capable of atomic imaging at magnetic field up to 35 T and capable of working at both 300 and 1.7 K low temperature; this is also the first water-cooled magnet STM capable of atomic imaging under 35 T magnetic field and huge vibrational conditions. Using this STM, we expect to investigate novel physical phenomena occurring under high in-plane magnetic fields.