Critical Correlations for Short-Range Valence-Bond Wave Functions on the Square Lattice

We investigate the arguably simplest $SU(2)$-invariant wave functions capable of accounting for spin-liquid behavior, expressed in terms of nearest-neighbor valence-bond states on the square lattice and characterized by different topological invariants. While such wave-functions are known to exhibit short-range spin correlations, we perform Monte Carlo simulations and show that four-point correlations decay algebraically with an exponent $1.16(4)$. This is reminiscent of the {\it classical} dimer problem, albeit with a slower decay. Furthermore, these correlators are found to be spatially modulated according to a wave-vector related to the topological invariants. We conclude that a recently proposed spin Hamiltonian that stabilizes the here considered wave-function(s) as its (degenerate) ground-state(s) should exhibit gapped spin and gapless non-magnetic excitations.Comment: 4 pages, 5 figures. Updated versio

Coexistence of long-range and algebraic correlations for short-range valence-bond wave functions in three dimensions

We investigate nearest-neighbor valence-bond wave functions on bipartite three-dimensional lattices. By performing large-scale Monte Carlo simulations, we find that long-range magnetic order coexists with dipolar four-spin correlations on the cubic lattice, this latter feature being reminiscent of the Coulomb phase for classical dimers on the same lattice. Similar properties are found for the lower-coordination diamond lattice. While this suggests that the coexistence of magnetic order and dipolar four-spin correlations is generic for bipartite three-dimensional lattices, we show that simple generalizations of these wave functions can encode different ordering behaviors.Comment: 4+ pages, 5 figures. Updated version, to appear in Phys. Rev. Let

ENCORE: An Extended Contractor Renormalization algorithm

Contractor renormalization (CORE) is a real-space renormalization-group method to derive effective Hamiltionians for microscopic models. The original CORE method is based on a real-space decomposition of the lattice into small blocks and the effective degrees of freedom on the lattice are tensor products of those on the small blocks. We present an extension of the CORE method that overcomes this restriction. Our generalization allows the application of CORE to derive arbitrary effective models whose Hilbert space is not just a tensor product of local degrees of freedom. The method is especially well suited to search for microscopic models to emulate low-energy exotic models and can guide the design of quantum devices.Comment: 5 pages, 4 figure

Quantum Critical Scaling of Fidelity Susceptibility

The behavior of the ground-state fidelity susceptibility in the vicinity of a quantum critical point is investigated. We derive scaling relations describing its singular behavior in the quantum critical regime. Unlike it has been found in previous studies, these relations are solely expressed in terms of conventional critical exponents. We also describe in detail a quantum Monte Carlo scheme that allows for the evaluation of the fidelity susceptibility for a large class of many-body systems and apply it in the study of the quantum phase transition for the transverse-field Ising model on the square lattice. Finite size analysis applied to the so obtained numerical results confirm the validity of our scaling relations. Furthermore, we analyze the properties of a closely related quantity, the ground-state energy's second derivative, that can be numerically evaluated in a particularly efficient way. The usefulness of both quantities as alternative indicators of quantum criticality is examined.Comment: 13 pages, 7 figures. Published versio

Phase separation versus supersolid behavior in frustrated antiferromagnets

We investigate the competition between spin-supersolidity and phase separation in a frustrated spin-half model of weakly coupled dimers. We start by considering systems of hard-core bosons on the square lattice, onto which the low-energy physics of the herein investigated spin model can be mapped, and devise a criterion for gauging the interplay between supersolid order and domain wall formation based on strong coupling arguments. Effective bosonic models for the spin model are derived via the contractor renormalization (CORE) algorithm and we propose to combine a self-consistent cluster mean-field solution with our criterion for the occurrence of phase separation to derive the phase diagram as a function of frustration and magnetic field. In the limit of strong frustration, the model is shown to be unstable toward phase separation, in contradiction with recently published results. However, a region of stable supersolidity is identified for intermediate frustration, in a parameter range not investigated so far and of possible experimental relevance.Comment: 8 pages, 7 figures. Published versio

Engineering exotic phases for topologically-protected quantum computation by emulating quantum dimer models

We use a nonperturbative extended contractor renormalization (ENCORE) method for engineering quantum devices for the implementation of topologically protected quantum bits described by an effective quantum dimer model on the triangular lattice. By tuning the couplings of the device, topological protection might be achieved if the ratio between effective two-dimer interactions and flip amplitudes lies in the liquid phase of the phase diagram of the quantum dimer model. For a proposal based on a quantum Josephson junction array [L. B. Ioffe {\it et al.}, Nature (London) {\bf 415}, 503 (2002)] our results show that optimal operational temperatures below 1 mK can only be obtained if extra interactions and dimer flips, which are not present in the standard quantum dimer model and involve three or four dimers, are included. It is unclear if these extra terms in the quantum dimer Hamiltonian destroy the liquid phase needed for quantum computation. Minimizing the effects of multi-dimer terms would require energy scales in the nano-Kelvin regime. An alternative implementation based on cold atomic or molecular gases loaded into optical lattices is also discussed, and it is shown that the small energy scales involved--implying long operational times--make such a device impractical. Given the many orders of magnitude between bare couplings in devices, and the topological gap, the realization of topological phases in quantum devices requires careful engineering and large bare interaction scales.Comment: 12 pages, 10 figure

Quantum Phase Diagram and Excitations for the One-Dimensional S=1 Heisenberg Antiferromagnet with Single-Ion Anisotropy

We investigate the zero-temperature phase diagram of the one-dimensional S=1 Heisenberg antiferromagnet with single-ion anisotropy. By employing high-order series expansions and quantum Monte Carlo simulations we obtain accurate estimates for the critical points separating different phases in the quantum phase diagram. Additionally, excitation spectra and gaps are obtained.Comment: 8 pages, 7 figures. Published versio

Transcriptome and gene expression analysis of three developmental stages of the coffee berry borer, Hypothenemus hampei

Coffee production is a global industry valued at approximately 173 billion US dollars. One of the main challenges facing coffee production is the management of the coffee berry borer (CBB), Hypothenemus hampei, which is considered the primary arthropod pest of coffee worldwide. Current control strategies are inefficient for CBB management. Although biotechnological alternatives, including RNA interference (RNAi), have been proposed in recent years to control insect pests, characterizing the genetics of the target pest is essential for the successful application of these emerging technologies. In this study, we employed RNA-seq to obtain the transcriptome of three developmental stages of the CBB (larva, female and male) to increase our understanding of the CBB life cycle in relation to molecular features. The CBB transcriptome was sequenced using Illumina Hiseq and assembled de novo. Differential gene expression analysis was performed across the developmental stages. The final assembly produced 29,434 unigenes, of which 4,664 transcripts were differentially expressed. Genes linked to crucial physiological functions, such as digestion and detoxification, were determined to be tightly regulated between the reproductive and nonreproductive stages of CBB. The data obtained in this study help to elucidate the critical roles that several genes play as regulatory elements in CBB development

Transcriptome and gene expression analysis of three developmental stages of the coffee berry borer, Hypothenemus hampei

Coffee production is a global industry valued at approximately 173 billion US dollars. One of the main challenges facing coffee production is the management of the coffee berry borer (CBB), Hypothenemus hampei, which is considered the primary arthropod pest of coffee worldwide. Current control strategies are inefficient for CBB management. Although biotechnological alternatives, including RNA interference (RNAi), have been proposed in recent years to control insect pests, characterizing the genetics of the target pest is essential for the successful application of these emerging technologies. In this study, we employed RNA-seq to obtain the transcriptome of three developmental stages of the CBB (larva, female and male) to increase our understanding of the CBB life cycle in relation to molecular features. The CBB transcriptome was sequenced using Illumina Hiseq and assembled de novo. Differential gene expression analysis was performed across the developmental stages. The final assembly produced 29,434 unigenes, of which 4,664 transcripts were differentially expressed. Genes linked to crucial physiological functions, such as digestion and detoxification, were determined to be tightly regulated between the reproductive and nonreproductive stages of CBB. The data obtained in this study help to elucidate the critical roles that several genes play as regulatory elements in CBB development

Transcriptome and gene expression analysis of three developmental stages of the coffee berry borer, Hypothenemus hampei

Coffee production is a global industry valued at approximately 173 billion US dollars. One of the main challenges facing coffee production is the management of the coffee berry borer (CBB), Hypothenemus hampei, which is considered the primary arthropod pest of coffee worldwide. Current control strategies are inefficient for CBB management. Although biotechnological alternatives, including RNA interference (RNAi), have been proposed in recent years to control insect pests, characterizing the genetics of the target pest is essential for the successful application of these emerging technologies. In this study, we employed RNA-seq to obtain the transcriptome of three developmental stages of the CBB (larva, female and male) to increase our understanding of the CBB life cycle in relation to molecular features. The CBB transcriptome was sequenced using Illumina Hiseq and assembled de novo. Differential gene expression analysis was performed across the developmental stages. The final assembly produced 29,434 unigenes, of which 4,664 transcripts were differentially expressed. Genes linked to crucial physiological functions, such as digestion and detoxification, were determined to be tightly regulated between the reproductive and nonreproductive stages of CBB. The data obtained in this study help to elucidate the critical roles that several genes play as regulatory elements in CBB development