Competition of Spinon Fermi Surface and Heavy Fermi Liquids states from the Periodic Anderson to the Hubbard model*

We study a model of correlated electrons coupled by tunnelling to a layer of itinerant electrons, which interpolates from a frustrated limit favorable to spin liquid states to a Kondo-lattice limit favorable to interlayer coherent heavy metallic states. Employing a slave rotor mean-field, we obtain a phase diagram and describe two regimes where the spin liquid state is destroyed by weak interlayer tunnelling, (i) the Kondo limit where the correlated electrons can be viewed as localized spin moments and (ii) near the Mott metal-insulator-transition where the spinon fermi surface transitions continuously into a Fermi liquid. We study the LDOS spectra of the correlated layer in the heavy Fermi liquid phase and describe the temperature dependence of its width arising from interactions and disorder effects. Comparison of theoretical results and recent experiments of the candidate spin liquid 1T-TaSe₂ residing on metallic 1H-TaSe₂ suggests that this system is either close to the localized Kondo limit, or in an intermediate coupling regime where the Kondo coupling and the Heisenberg exchange interaction are comparable, posing a challenge to the interpretation of this material as a candidate spin liquid.