Quantifying magnetic field driven lattice distortions in kagome metals at femto-scale using scanning tunneling microscopy*

A wide array of unusual phenomena has recently been uncovered in kagome solids. In particular, the charge density wave (CDW) state in the kagome superconductor AV₃Sb₅ (A = Cs, Rb, K) intrigued the community as it appears to break time-reversal symmetry despite the absence of spin magnetism. This has been tied to exotic orbital loop currents possibly intertwined with magnetic field tunable crystal distortions. To test this connection, precise determination of the lattice response to applied magnetic field is crucial, but can be challenging at the atomic-scale. We establish a new scanning tunneling microscopy based method to map the evolution of AV₃Sb₅ atomic structure as a function of the magnetic field. We study and discuss the response of both in-plane and out-of-plane lattice constants to 3D vector magnetic fields. The method substantially reduces errors present in typical STM measurements, and can be widely applied to extract the field-lattice coupling in other quantum materials.