We investigate a modified Anderson model at the large-$N$ limit, where Coulomb interaction is replaced by Sachdev-Ye-Kitaev random interaction. The resistivity of conduction electron $rho_{c}$ has a minimum value around temperature $widetilde{T}_{K}$
, which is similar to the Kondo system, but the impurity electrons density of state $A_{d}(omega)$ elucidates no sharp-peak like Kondo resonance around the Fermi surface. The impurity electrons entropy $S_{d}$ and specific heat capacity $C_{textrm{v}}$ illustrate a crossover from Fermi liquid to the non-Fermi liquid. The system is a non-Fermi liquid at temperature $T^{star}<T<widetilde{T}_{K}$, a Fermi liquid for $T<T^{star}$, and becomes a Fermi gas if $T>widetilde{T}_{K}$. The non-Fermi liquid at intermediate-$T$ regime does not occur in standard Anderson model. With renormalization group analysis, we elucidate a crossover from Fermi liquid to the non-Fermi liquid, coinciding with transport and thermodynamics. The resistivity minimum and the Kondo resonance are two characteristics of Kondo effect. However, the resistivity minimum emerges in our model when the system behaves as a NFL rather than FL, and the impurity electrons density of state without the Kondo resonance.
In this paper we introduce an exactly solvable Kondo lattice model without any fine-tuning local gauge symmetry. This model describes itinerant electrons interplaying with a localized magnetic moment via only longitudinal Kondo exchange. Its solvabil
ity results from conservation of the localized moment at each site, and is valid for arbitrary lattice geometry and electron filling. A case study on square lattice shows that the ground state is a N{e}el antiferromagnetic insulator at half-filling. At finite temperature, paramagnetic phases including a Mott insulator and correlated metal are found. The former is a melting antiferromagnetic insulator with a strong short-range magnetic fluctuation, while the latter corresponds to a Fermi liquid-like metal. Monte Carlo simulation and theoretical analysis demonstrate that the transition from paramagnetic phases into the antiferromagnetic insulator is a continuous $2D$ Ising transition. Away from half-filling, patterns of spin stripes (inhomogeneous magnetic order) at weak coupling, and phase separation at strong coupling are predicted. With established Ising antiferromagnetism and spin stripe orders, our model may be relevant to a heavy fermion compound CeCo(In$_{1-x}$Hg$_{x}$)$_{5}$ and novel quantum liquid-crystal order in a hidden order compound URu$_{2}$Si$_{2}$.
Quantum metrology employs quantum effects to attain a measurement precision surpassing the limit achievable in classical physics. However, it was previously found that the precision returns the shot-noise limit (SNL) from the ideal Zeno limit (ZL) du
e to the photon loss in quantum metrology based on Mech-Zehnder interferometer. Here, we find that not only the SNL can be beaten, but also the ZL can be asymptotically recovered in long-encoding-time condition when the photon dissipation is exactly studied in its inherent non-Markovian manner. Our analysis reveals that it is due to the formation of a bound state of the photonic system and its dissipative noise. Highlighting the microscopic mechanism of the dissipative noise on the quantum optical metrology, our result supplies a guideline to realize the ultrasensitive measurement in practice by forming the bound state in the setting of reservoir engineering.
We investigate the real-time dynamics of the half-filled one-dimensional extended Hubbard model in the strong-coupling regime, when driven by a transient laser pulse. Starting from a wide regime displaying a charge-density wave in equilibrium, a robu
st photoinduced in-gap state appears in the optical conductivity, depending on the parameters of the pulse. Here, by tuning its conditions, we maximize the overlap of the time-evolving wavefunction with excited states displaying the elusive bond-ordered wave of this model. Finally, we make a clear connection between the emergence of this order and the formation of the aforementioned in-gap state, suggesting the potential observation of purely electronic (i.e., not associated with a Peierls instability) bond-ordered waves in experiments involving molecular crystals.
Controlling the decoherence induced by the interaction of quantum system with its environment is a fundamental challenge in quantum technology. Utilizing Floquet theory, we explore the constructive role of temporal periodic driving in suppressing dec
oherence of a spin-1/2 particle coupled to a spin bath. It is revealed that, accompanying the formation of a Floquet bound state in the quasienergy spectrum of the whole system including the system and its environment, the dissipation of the spin system can be inhibited and the system tends to coherently synchronize with the driving. It can be seen as an analog to the decoherence suppression induced by the structured environment in spatially periodic photonic crystal setting. Comparing with other decoherence control schemes, our protocol is robust against the fluctuation of control parameters and easy to realize in practice. It suggests a promising perspective of periodic driving in decoherence control.
Motivated by recent work of Mross and Senthil [Phys. Rev. B textbf{84}, 165126 (2011)] which provides a dual description for Mott transition from Fermi liquid to quantum spin liquid in two space dimensions, we extend their approach to higher dimensio
nal cases, and we provide explicit formalism in three space dimensions. Instead of the vortices driving conventional Fermi liquid into quantum spin liquid states in 2D, it is the vortex lines to lead to the instability of Fermi liquid in 3D. The extended formalism can result in rich consequences when the vortex lines condense in different degrees of freedom. For example, when the vortex lines condense in charge phase degrees of freedom, the resulting effective fermionic action is found to be equivalent to that obtained by well-studied slave-particle approaches for Hubbard and/or Anderson lattice models, which confirm the validity of the extended dual formalism in 3D. When the vortex lines condense in spin phase degrees of freedom, a doublon metal with a spin gap and an instability to the unconventional superconducting pairing can be obtained. In addition, when the vortex lines condense in both phase degrees, an exotic doubled U(1) gauge theory occurs which describes a separation of spin-opposite fermionic excitations. It is noted that the first two features have been discussed in a similar way in 2D, the last one has not been reported in the previous works. The present work is expected to be useful in understanding the Mott transition happening beyond two space dimensions.
An unstable particle in quantum mechanics can be stabilized by frequent measurements, known as the quantum Zeno effect. A soliton with dissipation behaves like an unstable particle. Similar to the quantum Zeno effect, here we show that the soliton ca
n be stabilized by modulating periodically dispersion, nonlinearity, or the external harmonic potential available in BEC. This can be obtained by analyzing a Painleve integrability condition, which results from the rigorous Painleve analysis of the generalized nonautonomous nonlinear Schrodinger equation. The result has a profound implication to the optical soliton transmission and the matter-wave soliton dynamics.
