Pattern Formation in One-Dimensional Polaron Systems and Temporal Orthogonality Catastrophe

Recent studies have demonstrated that higher than two-body bath-impurity correlations are not important for quantitatively describing the ground state of the Bose polaron. Motivated by the above, we employ the so-called Gross Ansatz (GA) approach to unravel the stationary and dynamical properties of the homogeneous one-dimensional Bose-polaron for different impurity momenta and bath-impurity couplings. We explicate that the character of the equilibrium state crossovers from the quasi-particle Bose polaron regime to the collective-excitation stationary dark-bright soliton for varying impurity momentum and interactions. Following an interspecies interaction quench the temporal orthogonality catastrophe is identified, provided that bath-impurity interactions are sufficiently stronger than the intraspecies bath ones, thus generalizing the results of the confined case. This catastrophe originates from the formation of dispersive shock wave structures associated with the zero-range character of the bath-impurity potential. For initially moving impurities, a momentum transfer process from the impurity to the dispersive shock waves via the exerted drag force is demonstrated, resulting in a final polaronic state with reduced velocity. Our results clearly demonstrate the crucial role of non-linear excitations for determining the behavior of the one-dimensional Bose polaron.

Quasi-particle interference of the van Hove singularity in Sr2RuO4

The single-layered ruthenate Sr2RuO4 is one of the most enigmatic unconventional superconductors. While for many years it was thought to be the best candidate for a chiral p-wave superconducting ground state, desirable for topological quantum computations, recent experiments suggest a singlet state, ruling out the original p-wave scenario. The superconductivity as well as the properties of the multi-layered compounds of the ruthenate perovskites are strongly influenced by a van Hove singularity in proximity of the Fermi energy. Tiny structural distortions move the van Hove singularity across the Fermi energy with dramatic consequences for the physical properties. Here, we determine the electronic structure of the van Hove singularity in the surface layer of Sr2RuO4 by quasi-particle interference imaging. We trace its dispersion and demonstrate from a model calculation accounting for the full vacuum overlap of the wave functions that its detection is facilitated through the octahedral rotations in the surface layer.

Dynamics of Langmuir Wave Spectra in Randomly Inhomogeneous Solar Wind Plasmas

Solar coronal and wind plasmas often contain density fluctuations of various scales and amplitudes. The scattering of Langmuir wave turbulence on these inhomogeneities modifies the properties of the radiated electromagnetic emissions traveling from the Sun to the Earth. This paper shows the similarities between the physical results obtained by (i) a model based on the Zakharov equations, describing the self-consistent dynamics of Langmuir wave turbulence spectra in a plasma with external density fluctuations, and (ii) a modeling, within the framework of geometric optics approximation, of quasi-particles (representing plasmon quanta) moving in a fluctuating potential. It is shown that the dynamics of the Langmuir spectra is governed by anomalous diffusion processes, as a result of multiple scattering of waves on the density fluctuations; the same dynamics are observed in the momenta distributions of quasi-particles moving in potential structures with random inhomogeneities. These spectra and distributions are both characterized by a fast broadening during which energy is transported to larger wavevectors and momenta, exhibiting nonlinear time dependence of the average squares of wavevectors and quasi-particle momenta as well as non-Gaussian tails in the asymptotic stage. The corresponding diffusion coefficients depend on the time and are proportional to the square of the average level of density (or potential) fluctuations. It appears that anomalous transport and superdiffusion phenomena are responsible for the spectral broadening.

Charge transport spectra in superconductor-InAs/GaSb-superconductor heterostructures

Charge transport physics in InAs/GaSb bi-layer systems has recently attracted attention for the experimental search for two-dimensional topological superconducting states in solids. Here we report measurement of charge transport spectra of nano devices consisting of an InAs/GaSb quantum well sandwiched by tantalum superconductors. We explore the current-voltage relation as a function of the charge-carrier density in the quantum well controlled by a gate voltage and an external magnetic field. We observe three types of differential resistance peaks, all of which can be effectively tuned by the external magnetic field, and, however, two of which appear at electric currents independent of the gate voltage, indicating a dominant mechanism from the superconductor and the system geometry. By analyzing the spectroscopic features, we nd that the three types of peaks identify Andreev reflections, quasi-particle interference, and superconducting transitions in the device, respectively. Our results provide a basis for further exploration of possible topological superconducting state in the InAs/GaSb system.

Semiconducting phase of hafnium dioxide under high pressure: a theoretical studied by quasi-particle GW calculations

The phase stability of the hafnium dioxide compounds HfO2, a novelmaterial with a wide range of application due to its versatility and biocompatibility,is predicted to be achievable by using evolutionary technique, based on first-principlescalculations. Herein, the candidate structure of HfO2 is revealed to adopt a tetragonalstructure under high-pressure phase with P4/nmm space group. This evidentlyconfirms the stability of the HfO2 structures, since the decomposition into thecomponent elements under pressure does not occur until the pressure is at least200GPa. Moreover, phonon calculations can confirm that the P4/nmm structure isdynamically stable. The P4/nmm structure is mainly attributed to the semiconductingproperty within using the Perdew{Burke{Ernzerhof, the modified Becke-Johnsonexchange potential in combination with the generalized gradient approximations, andthe quasi-particle GW approximation, respectively. Our calculation manifests that theP4/nmm structure likely to be metal above 200GPa, arising particularly from GWapproximation. The remarkable results of this work provide more understanding ofthe high-pressure structure for designing metal-oxide-based semiconducting materials.

Evidence for an atomic chiral superfluid with topological excitations

Topological superfluidity is an important concept in electronic materials as well as ultracold atomic gases1. However, although progress has been made by hybridizing superconductors with topological substrates, the search for a material—natural or artificial—that intrinsically exhibits topological superfluidity has been ongoing since the discovery of the superfluid 3He-A phase2. Here we report evidence for a globally chiral atomic superfluid, induced by interaction-driven time-reversal symmetry breaking in the second Bloch band of an optical lattice with hexagonal boron nitride geometry. This realizes a long-lived Bose–Einstein condensate of 87Rb atoms beyond present limits to orbitally featureless scenarios in the lowest Bloch band. Time-of-flight and band mapping measurements reveal that the local phases and orbital rotations of atoms are spontaneously ordered into a vortex array, showing evidence of the emergence of global angular momentum across the entire lattice. A phenomenological effective model is used to capture the dynamics of Bogoliubov quasi-particle excitations above the ground state, which are shown to exhibit a topological band structure. The observed bosonic phase is expected to exhibit phenomena that are conceptually distinct from, but related to, the quantum anomalous Hall effect3–7 in electronic condensed matter.