Scanning Quantum Cryogenic Atom Microscope (1608.06922v4)

Abstract: Microscopic imaging of local magnetic fields provides a window into the organizing principles of complex and technologically relevant condensed matter materials. However, a wide variety of intriguing strongly correlated and topologically nontrivial materials exhibit poorly understood phenomena outside the detection capability of state-of-the-art high-sensitivity, high-resolution scanning probe magnetometers. We introduce a quantum-noise-limited scanning probe magnetometer that can operate from room to cryogenic temperatures with unprecedented DC-field sensitivity and micron-scale resolution. The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) employs a magnetically levitated atomic Bose-Einstein condensate (BEC), thereby providing immunity to conductive and blackbody radiative heating. It has a field sensitivity of 1.4 nT per resolution-limited point ($\sim$2 $\mu$m), or 6 nT/$\sqrt{\text{Hz}}$ per point at its duty cycle. Compared to point-by-point sensors, the long length of the BEC provides a naturally parallel measurement, allowing one to measure nearly one-hundred points with an effective field sensitivity of 600 pT$/\sqrt{\text{Hz}}$ for each point during the same time as a point-by-point scanner would measure these points sequentially. Moreover, it has a noise floor of 300 pT and provides nearly two orders of magnitude improvement in magnetic flux sensitivity (down to $10^{-6}$ $\Phi_0/\sqrt{\text{Hz}}$) over previous atomic probe magnetometers capable of scanning near samples. These capabilities are, for the first time, carefully benchmarked by imaging magnetic fields arising from microfabricated wire patterns, in a system where samples may be scanned, cryogenically cooled, and easily exchanged. The SQCRAMscope will provide charge transport images at temperatures from room to 4 K in unconventional superconductors and topologically nontrivial materials.