Fe-Vacancies Manipulate Kondo Screening States in the d-Orbital Kondo Lattice of Fe3-xGeTe2 (x = 0.07-0.54)

Manipulating the electronic correlation is a long-term issue in the Kondo regime. Based on the pioneer successes in many localized f-orbital systems, further achievements in more itinerant d-orbital systems will open up avenues for numerous systems to participate in enabling the understanding of the electron interactions toward quantum criticality. Here, by simply tuning the ratio of Fe vacancies (x) in d-orbital Fe3-xGeTe2 (x = 0.07-0.54), the effective mass of Kondo lattice (KL) Fe3-xGeTe2 is modulated due to the change of spinless Kondo hole densities, through a series of scaling investigations including on the effective and spontaneous moments mu (eff )and mu (spon), magnetic susceptibility chi, the Sommerfeld coefficient gamma, and the resistivity coefficients A. By analyzing the Fermi liquid characteristics of KL via the two relations of A(FL)/gamma(2) and chi(Pauli)(0)/gamma below T*, an orbital coupling between degenerate orbitals of local moment S and multiple conducting spins m are found. With increasing Fe vacancy concentration, the localization effect, and Kondo interactions can be manipulated simultaneously, and the change in 2S/m leads to a subtle over-under-over- Kondo screening states evolution in Fe3-xGeTe2. This work expands the comprehension of Kondo screening and provides a facile method to control electron correlation.