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Register a new userDynamics of a quantum phase transition in the Aubry-Andr{e}-Harper model with $p$-wave superconductivity
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We investigate the nonequilibrium dynamics of the one-dimension Aubry-Andr{e}-Harper model with $p$-wave superconductivity by changing the potential strength with slow and sudden quench. Firstly, we study the slow quench dynamics from localized phase to critical phase by linearly decreasing the potential strength $V$. The localization length is finite and its scaling obeys the Kibble-Zurek mechanism. The results show that the second-order phase transition line shares the same critical exponent $z u$, giving the correlation length $ u=0.997$ and dynamical exponent $z=1.373$, which are different from the Aubry-Andr{e} model. Secondly, we also study the sudden quench dynamics between three different phases: localized phase, critical phase, and extended phase. In the limit of $V=0$ and $V=infty$, we analytically study the sudden quench dynamics via the Loschmidt echo. The results suggest that, if the initial state and the post-quench Hamiltonian are in different phases, the Loschmidt echo vanishes at some time intervals. Furthermore, we found that, if the initial value is in the critical phase, the direction of the quench is the same as one of the two limits mentioned before, and similar behaviors will occur.
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Off-diagonal Aubry-Andr{e} (AA) model has recently attracted a great deal of attention as they provide condensed matter realization of topological phases. We numerically study a generalized off-diagonal AA model with p-wave superfluid pairing in the presence of both commensurate and incommensurate hopping modulations. The phase diagram as functions of the modulation strength of incommensurate hopping and the strength of the p-wave pairing is obtained by using the multifractal analysis. We show that with the appearance of the p-wave pairing, the system exhibits mobility-edge phases and critical phases with various number of topologically protected zero-energy modes. Predicted topological nature of these exotic phases can be realized in a cold atomic system of incommensurate bichromatic optical lattice with induced p-wave superfluid pairing by using a Raman laser in proximity to a molecular Bose-Einstein condensation.
In this work, the non-Markovian dynamics of excitation in the generalized Aubry-Andr{e}-Harper model coupled with an Ohmic-type environment is discussed in detail by evaluating the survival probability and inverse participation ratio of the state of system. Contrary to the common belief that localization will preserve the information of the initial state in the system against dissipation into the environment, this study found that strong localization can enhance the dissipation of quantum information. Through a thorough examination, we show that the non-Markovianity induced by the memory effect of the environment was responsible for this behavior. Under this circumstance, the exchange of energy between the system and its environment may lead to interference in the reduced energy levels of the system, that are also responsible for the stability of the system. In term of strong localization, the difference between reduced energy levels will become large, to the degree that the environment cannot feed back enough energy into the system. As a result, the initial-state information will eventually dissipate. This explanation was verified herein by an increase of the coupling strength between the system and its environment, which greatly reduced the decaying of quantum information.
We study the many-body localization (MBL) transition of Floquet eigenstates in a driven, interacting fermionic chain with an incommensurate Aubry-Andr{e} potential and a time-periodic hopping amplitude as a function of the drive frequency $omega_D$ using exact diagonalization (ED). We find that the nature of the Floquet eigenstates change from ergodic to Floquet-MBL with increasing frequency; moreover, for a significant range of intermediate $omega_D$, the Floquet eigenstates exhibit non-trivial fractal dimensions. We find a possible transition from the ergodic to this multifractal phase followed by a gradual crossover to the MBL phase as the drive frequency is increased. We also study the fermion auto-correlation function, entanglement entropy, normalized participation ratio (NPR), fermion transport and the inverse participation ratio (IPR) as a function of $omega_D$. We show that the auto-correlation, fermion transport and NPR displays qualitatively different characteristics (compared to their behavior in the ergodic and MBL regions) for the range of $omega_D$ which supports multifractal eigenstates. In contrast, the entanglement growth in this frequency range tend to have similar features as in the MBL regime; its rate of growth is controlled by $omega_D$. Our analysis thus indicates that the multifractal nature of Floquet-MBL eigenstates can be detected by studying auto-correlation function and fermionic transport of these driven chains. We support our numerical results with a semi-analytic expression of the Floquet Hamiltonian obtained using Floquet perturbation theory (FPT) and discuss possible experiments which can test our predictions.
We study a non-Hermitian AA model with the long-range hopping, $1/r^a$, and different choices of the quasi-periodic parameters $beta$ to be the member of the metallic mean family. We find that when the power-law exponent is in the $a<1$ regime, the system displays a delocalized-to-multifractal (DM) edge in its eigenstate spectrum. For the $a>1$ case, it exists a delocalized-to-localized (DL) edge, also called the mobility edge. While a striking feature of the Hermitian AA model with the long-range hopping is that the fraction of delocalized states can be obtained from a general sequence manifesting a mathematical feature of the metallic mean family, we find that the DM or DL edge for the non-Hermitian cases is independent of the mathematical feature of the metallic mean family. To understand this difference, we consider a specific case of the non-Hermitian long-range AA model with $a=2$, for which we can apply the Sarnak method to analytically derive its localization transition points and the exact expression of the DL edge. Our analytical result clearly demonstrates that the mobility edge is independent of the quasi-periodic parameter $beta$, which confirms our numerical result. Finally, an optical setup is proposed to realize the non-Hermitian long-range AA model.
We study a class of off-diagonal quasiperiodic hopping models described by one-dimensional Su-Schrieffer-Heeger chain with quasiperiodic modulations. We unveil a general dual-mapping relation in parameter space of the dimerization strength $lambda$ and the quasiperiodic modulation strength $V$, regardless of the specific details of the quasiperiodic modulation. Moreover, we demonstrated semi-analytically and numerically that under the specific quasiperiodic modulation, quantum criticality can emerge and persist in a wide parameter space. These unusual properties provides a distinctive paradigm compared with the diagonal quasiperiodic systems.
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