Characterizing Featureless Mott Insulating State by Quasiparticle Interferences - A Dynamical Mean Field Theory Prospect

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The quasiparticle interferences (QPIs) of a Mott insulator are investigated using the T-matrix formalism implemented with the dynamical mean-field theory (T-DMFT). In Mott insulating state, because DMFT predicts a singularity in the real part of the electron self energy Σ(ω) η/ω at low frequency, where η can be considered as the 'order parameter' for Mott insulating state, QPIs are completely washed out at the small bias voltage. However, a further analysis shows that Σ(ω) in fact serves as an energy-dependent chemical potential shift. As a result, the effective bias voltage seen by the system is eV' = eV - Σ(eV). Due to the singular behavior of Σ(ω), a critical bias voltage eVc = √η satisfying eV'=0 exists if and only if in Mott insulating state. Consequently, the same QPI patterns produced by the non-interacting Fermi surfaces appears at this critical bias voltage eVc in Mott insulating state. We propose that this reentry of non-interacting QPI patterns at eVc could serve as an experimental signature of Mott insulating state, and the 'order parameter' can be experimentally measured as η (eVc)².