Exact diagonalization study of the trionic crossover and the trion liquid in the attractive three-component Hubbard model

摘要

We investigate the trion formation and the effective trionic properties inthe attractive Hubbard model with three fermionic colors using exactdiagonalization. The crossover to the trionic regime with colorless compoundfermions upon increasing strength of the onsite attraction parameter U featuressmoothly evolving ground state properties and exhibits clear similarities tothe BCS/BEC-crossover for two colors. In the excitation spectrum, there is aclear gap opening between a band of well-defined trions and excitations ofbroken-up trions at U_c ~ 1.8t. This picture remains the same away from theSU(3)-symmetric point. The spatial pairing correlations for colored Cooperpairs are compatible with a power-law at small attractions and change to anexponential decay above the trionic crossover. Furthermore, we show that theeffective trionic liquid for U > U_c can be well modeled with spinless 'heavy'fermions interacting with a strong nearest neighbor repulsion.