Quantum criticality and universality in the $p$-wave paired Aubry-André-Harper model

We investigate the quantum criticality and universality in Aubry-André-Harper (AAH) model with $p$-wave superconducting pairing $Δ$ in terms of the generalized fidelity susceptibility (GFS). We show that the higher-order GFS is more efficient in spotlighting the critical points than lower-order ones, and thus the enhanced sensitivity is propitious for extracting the associated universal information from the finite-size scaling in quasiperiodic systems. The GFS obeys power-law scaling for localization transitions and thus scaling properties of the GFS provide compelling values of critical exponents. Specifically, we demonstrate that the fixed modulation phase $ϕ=π$ alleviates the odd-even effect of scaling functions across the Aubry-André transition with $Δ=0$, while the scaling functions for odd and even numbers of system sizes with a finite $Δ$ cannot coincide irrespective of the value of $ϕ$. A thorough numerical analysis with odd number of system sizes reveals the correlation-length exponent $ν\simeq 1.000$ and the dynamical exponent $z$ $\simeq$ 1.388 for transitions from the critical phase to the localized phase,suggesting the unusual universality class of localization transitions in the AAH model with a finite $p$-wave superconducting pairing lies in a different universality class from the Aubry-André transition. The results may be testified in near term state-of-the-art experimental settings.

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