Observation of magnon bound states in the long-range, anisotropic Heisenberg model

Over the recent years coherent, time-periodic modulation has been established as a versatile tool for realizing novel Hamiltonians. Using this approach, known as Floquet engineering, we experimentally realize a long-ranged, anisotropic Heisenberg model with tunable interactions in a trapped ion quantum simulator. We demonstrate that the spectrum of the model contains not only single magnon excitations but also composite magnon bound states. For the long-range interactions with the experimentally realized power-law exponent, the group velocity of magnons is unbounded. Nonetheless, for sufficiently strong interactions we observe bound states of these unconventional magnons which possess a non-diverging group velocity. By measuring the configurational mutual information between two disjoint intervals, we demonstrate the implications of the bound state formation on the entanglement dynamics of the system. Our observations provide key insights into the peculiar role of composite excitations in the non-equilibrium dynamics of quantum many-body systems

Symmetry breaking and circular photogalvanic effect in epitaxial CdxHg1-xTe films

We report on the observation of symmetry breaking and the circular photogalvanic effect in CdxHg1-xTe alloys. We demonstrate that irradiation of bulk epitaxial films with circularly polarized terahertz radiation leads to the circular photogalvanic effect (CPGE) yielding a photocurrent whose direction reverses upon switching the photon helicity. This effect is forbidden in bulk zinc-blende crystals by symmetry arguments; therefore, its observation indicates either the symmetry reduction of bulk material or that the photocurrent is excited in the topological surface states formed in a material with low cadmium concentration. We show that the bulk states play a crucial role because the CPGE was also clearly detected in samples with noninverted band structure. We suggest that strain is a reason for the symmetry reduction. We develop a theory of the CPGE showing that the photocurrent results from the quantum interference of different pathways contributing to the free-carrier absorption (Drude-like) of monochromatic radiation

Ethnic Speech and Ethnic Action as Ethnic Behavior: Part 1. Construction of the Brunel Ethnic Behavior Inventory

© 2016 Taylor & Francis.This article reports the construction of a new survey—specifically, the Brunel Ethnic Behavior Inventory (BEBI)—designed to measure ethnic speech and ethnic action as separate, yet related, aspects of individuals’ ethnic behavior. Using Tajfel’s social identity theory as a conceptual frame of reference, this study sought an answer to the research question of how many factors actually are measured by the BEBI, and tested the hypothesis that a two-factor model (i.e., Ethnic Speech and Ethnic Action as two correlated factors) would provide significantly better goodness of fit to the correlational data than would a one-factor model (i.e., Ethnic Behavior as one undifferentiated factor). Across one pilot sample (n = 101) and two main samples (n = 120 for Sample 1, n = 148 for Sample 2), the study found that not only did the BEBI measure two factors at most (i.e., Ethnic Speech and Ethnic Action) but, consistent with the hypothesis, the two-factor model yielded better goodness of fit than did the one-factor model. Implications for the conceptualization and measurement of Verkuyten’s “ways of ethnicity” are discussed

Deconfined quantum criticality in the long-range, anisotropic Heisenberg chain

Deconfined quantum criticality describes continuous phase transitions that are not captured by the Landau-Ginzburg paradigm. Here, we investigate deconfined quantum critical points in the long-range, anisotropic Heisenberg chain. With matrix product state simulations, we show that the model undergoes a continuous phase transition from a valence bond solid to an antiferromagnet. We extract the critical exponents of the transition and connect them to an effective field theory obtained from bosonization techniques. We show that beyond stabilizing the valance bond order, the long-range interactions are irrelevant and the transition is well described by a double frequency sine-Gordon model. We propose how to realize and probe deconfined quantum criticality in our model with trapped-ion quantum simulators

Deconfined Quantum Criticality in the long-range, anisotropic Heisenberg Chain

<p>Deconfined quantum criticality describes continuous phase transitions that are not captured by the Landau-Ginzburg paradigm. Here, we investigate deconfined quantum critical points in the long-range, anisotropic Heisenberg chain. With matrix product state simulations, we show that the model undergoes a continuous phase transition from a valence bond solid to an antiferromagnet. We extract the critical exponents of the transition and connect them to an effective field theory obtained from bosonization techniques. We show that beyond stabilizing the valance bond order, the  long-range interactions are irrelevant and the transition is well described by a double frequency sine-Gordon model. We propose how to realize and probe deconfined quantum criticality in our model with trapped-ion quantum simulators.</p&gt

Signatures of Confinement in Raman Spectroscopy of Ising Spin Chains

<p>Confinement of excitations is usually considered as a phenomenon of high-energy physics. How-<br> ever, over the recent years, related effects have been discussed in condensed matter settings as well.<br> A paradigmatic example is the formation of mesonic bound states in spin chains with linear con-<br> finement between domain walls. A prominent candidate material is the quasi-one dimensional Ising<br> magnet CoNb2O6 for which mesonic bound states have been detected by neutron scattering exper-<br> iments. In this work, we study the Raman response of a twisted Kitaev chain in the presence of a<br> magnetic field as a minimal model for confinement in CoNb2O6 and compute the response within<br> the theory by Fleury and Loudon. We show that the bound states directly manifest themselves as<br> sharp peaks in the Raman response, which we numerically compute using Matrix Product States.<br> We find that the main features of the spectrum can be well understood by a trial wave-function,<br> which contains a few solitonic excitations only. Moreover, when approaching the critical regime<br> Raman spectroscopy can be used to directly detect Ising quantum criticality via the emergence of<br> the famous E8 symmetry in the response spectrum.</p&gt

Characterizing Topological Excitations of a Long-Range Heisenberg Model with Trapped Ions

Realizing and characterizing interacting topological phases in synthetic quantum systems is a formidable challenge. Here, we propose a Floquet protocol to realize the antiferromagnetic Heisenberg model with power-law decaying interactions. Based on analytical and numerical arguments, we show that this model features a quantum phase transition from a liquid to a valence bond solid that spontaneously breaks lattice translational symmetry and is reminiscent of the Majumdar-Ghosh state. The different phases can be probed dynamically by measuring the evolution of a fully dimerized state. We moreover introduce an interferometric protocol to characterize the topological excitations and the bulk topological invariants of the interacting many-body system.Comment: 13 pages, 12 figures, revised version contains significantly extended discussion of the implementation of the Zak protoco

Polish Medical Doctors’ Opinions on Available Resources and Information Campaigns concerning Antibiotics and Antibiotic Resistance, a Cross-Sectional Study

Background: Antibiotic resistance (ABR) is at the top of global health threats. This paper aims to assess Polish physicians’ readiness to impact ABR through prescribing routines. Methods: Surveying Polish physicians participating in specialization courses at the Center for Postgraduate Medical Education in Warsaw, Poland from October 2019 to March 2020. Results: Information was obtained from 504 physicians aged 25–59, mean 32.8 ± 5.9 years, mainly women (65%). Most doctors (78%) prescribed antibiotics at least once a week. Physicians indicated clinical practice guidelines as resources most often consulted in the management of infections (90%). However, clinical experience was also declared a powerful resource. In total, 54% of respondents recalled receiving information about the prudent use of antibiotics within 12 months, which partially translated into changing views (56%) and practice (42%). Physicians disagreed that national campaigns provide good promotion of prudent antibiotics use (75%) or that they are effective (61%). Only 40% of doctors were aware of the national campaign promoting responsible antibiotics use, 24% had heard about the European Antibiotic Awareness Day and 20% knew about the World Antimicrobial Awareness Week. Conclusions: Prescribers most often rely on clinical practice guidelines and their own experience as resources for antibiotics use. Doctors’ awareness of available resources and information campaigns concerning antibiotics and antibiotic resistance should be improved