Abstract
This thesis presents a systematic investigation of exotic correlated electronic states and hidden charge orders in kagome lattice metals and rare-earth tritelluride LaTe3, studied by low-temperature scanning tunneling microscopy (STM) and complemented with angle-resolved photoemission spectroscopy (ARPES) and thin-film molecular beam epitaxy (MBE). In Fedoped CoSn kagome films, chemical doping continuously tunes the filling of geometrically frustrated flat bands. We discover a temperature-driven cascade of strongly correlated phases, including electronic nematic order and an orbital-selective Mott state at half filling of the upper flat band. A phase-sensitive lock-in tunneling spectroscopy technique is developed to probe local electronic incompressibility at the atomic scale, verifying the Hubbard band origin of the Mott state. In the kagome metal CsV3Sb5, individual magnetic Co adatoms are deployed as local quantum sensors to probe the hidden order within the 2a × 2a charge density wave (CDW). A localized in-gap quasiparticle excitation is observed below 30 K, consistent with a flux defect in a time-reversal symmetry-breaking loop-current state. We further discover an odd-parity f-wave charge bond order with q = 0, which breaks the inversion symmetry, gaps a Dirac point along the Γ−K line, and realizes the Gross-Neveu dynamical generation scenario. This f-wave phase is an intervening state, vanishing abruptly below 10 K into an unresolved hidden ground state. In LaTe3, deposited Co atoms amplify quasiparticle interference signals. Combining with polarization-resolved ARPES, we reveal that the unidirectional CDW carries a substantial ferroaxial component, driven by inter-orbital coupling and breaking all vertical mirror symmetries. This work establishes single-atom spectroscopic probing as a versatile methodology for uncovering hidden electronic orders, advancing understanding of the interplay between geometry, orbital degrees of freedom, and electronic correlations in quantum materials.