Out-of-Equilibrium Dissipative <i>ac</i>—Susceptibility in Quantum Ising Spin Glass

The imaginary part of the non-equilibrium magnetic susceptibility of Ising spin glass in a transverse field under time-dependent longitudinal external magnetic field has been calculated at very low temperature on the basis of quantum droplet model and quantum linear response theory. Quantum and aging effects on the low temperature dynamics of the model are discussed. A comparison with recent theoretical and experimental data in spin glass is made.

Scattering and absorption imaging of a highly fractured fluid-filled seismogenetic volume in a region of slow deformation

Regions of slow strain often produce swarm-like sequences,characterized by the lack of a clear mainshockaftershock pattern.The comprehension of their underlying physical mechanisms is challenging and still debated.We used seismic recordings from the last Pollino swarm(2010-2014) and nearby to separate and map seismic scattering(from P peak-delays) and absorption(from late-time coda-wave attenuation) at different frequencies in the Pollino range and surroundings.High-scattering and high-absorption anomalies are markers of a fluid-filled fracture volume extending from SE to NW(1.5-6 Hz) across the range.With increasing frequency,these anomalies approximately cover the area where the strongest earthquakes occurred from the sixteenth century until 1998.In our interpretation,the NW fracture propagation ends where carbonates of the Lucanian Apennines begin,as marked by a high-scattering and low-absorption area.At the highest frequency(12 Hz) the anomalies widen southward in the middle of the range,consistently marking the faults active during the recent Pollino swarm.Our results suggest that fracture healing has closed small-scale fractures across the SE faults that were active in the past centuries,and that the propagation of fluids may have played a crucial role in triggering the 2010-2014 Pollino swarm.Assuming that the fluid propagation ended at the carbonates barrier in the NW direction,fractures opened new paths to the South,favoring the nucleation of the last Pollino swarm.Indeed,the recently active faults in the middle of the seismogenic volume are marked by a high-scattering and highabsorption footprints.Our work provides evidence that attenuation parameters may track shape and dynamics of fluid-filled fracture networks in fault areas.

An analytical variational method for the biased quantum Rabi model in the ultra-strong coupling regime

An analytical variational method for the ground state of the biased quantum Rabi model in the ultra-strong coupling regime is presented. This analytical variational method can be obtained by a unitary transformation or alternatively by assuming the form of the ground state wave function. The key of the method is to introduce a variational parameter λ,which can be determined by minimizing the energy functional. Using this method, we calculate the physical observables with high accuracy in comparison with the numerical exact ones. Our method evidently improves over the widely used general rotating-wave approximation（GRWA） in both qualitative and quantitative aspects.

Time delay in non-lethal infectious diseases

The effects of the incubation period q on the dynamics of non-lethal infectious diseases in a fixed-size population are studied by means of a delay differential equation model. It is noted that the ratio between the quantity q and the time τ for recovering from the illness plays an important role in the onset of the epidemic breakthrough. An approximate analytic expression for the solution of the delay differential equation governing the dynamics of the system is proposed and a comparison is made with the classical SEIR model.

Quantum Interference in Josephson Junctions

The parallelism between diffraction and interference in optics and quantum interference in Josephson junctions is discussed and studied in details. The interdisciplinary character of the present work is highlighted through specific examples. The Fraunhofer-like pattern of the maximum Josephson current in a single Josephson junction and the periodic field dependence of the critical current in two-junction and in multi-junction quantum interferometers is analyzed and discussed in comparison with the homologous classical optical phenomena.

Gate-controlled supercurrent effect in dry-etched Dayem bridges of non-centrosymmetric niobium rhenium

The application of a gate voltage to control the superconducting current flowing through a nanoscale superconducting constriction,named as gate-controlled supercurrent(GCS),has raised great interest for fundamental and technological reasons.To gain a deeper understanding of this effect and develop superconducting technologies based on it,the material and physical parameters crucial for the GCS effect must be identified.Top-down fabrication protocols should also be optimized to increase device scalability,although studies suggest that top-down fabricated devices are more resilient to show a GCS.Here,we investigate gated superconducting nanobridges made with a top-down fabrication process from thin films of the noncentrosymmetric superconductor niobium rhenium with varying ratios of the constituents(NbRe).Unlike other devices previously reported and made with a top-down approach,our NbRe devices systematically exhibit a GCS effect when they were fabricated from NbRe thin films with small grain size and etched in specific conditions.These observations pave the way for the realization of top-down-made GCS devices with high scalability.Our results also imply that physical parameters like structural disorder and surface physical properties of the nanobridges,which can be in turn modified by the fabrication process,are crucial for a GCS observation,providing therefore also important insights into the physics underlying the GCS effect.