Coexisting low-energy scales are observed in f -electron materials. The information about some of... more Coexisting low-energy scales are observed in f -electron materials. The information about some of low-energy scales is imprinted in the electron self-energy, which can be measured by angle-resolved photoemission (ARPES). Such measurements in d-electron materials over the last decade were based on high energy-and momentumresolution ARPES techniques used to extract the self-energy information from measured spectra. Simultaneously, many-body theoretical approaches have been developed to find a link between the self-energy and many-body interactions. Here we show the transcription of such methods from d-electrons to f -electrons by presenting the first example of low energy scales in the f -electron material USb2, measured with synchrotron-based ARPES. The proposed approach will help in answering the fundamental questions about the complex nature of the heavy fermion state.
We report measurements of the specific heat of the quantum spin liquid system SrCu2(BO3)2 in cont... more We report measurements of the specific heat of the quantum spin liquid system SrCu2(BO3)2 in continuous magnetic fields H of up to 33 T. The specific heat data, when combined with a finite temperature Lanczos diagonalization of the Shastry-Sutherland Hamiltonian, indicates the presence of a nearest neighbor Dzyaloshinsky-Moriya (DM) interaction that violates the crystal symmetry for H = 0. Moreover, the same DM interaction is required to explain the observed ESR lines for H c. These results indicate that spin-lattice coupling needs to be included in any realistic description of this system.
We introduce a frustrated spin 1/2 Hamiltonian which is an extension of the two dimensional J1 −J... more We introduce a frustrated spin 1/2 Hamiltonian which is an extension of the two dimensional J1 −J2 Heisenberg model. The ground states of this model are exactly obtained at a first order quantum phase transition between two regions with different valence bond solid order parameters. At this point, the low energy excitations are deconfined spinons and spin-charge separation occurs under doping in the limit of low concentration of holes. In addition, this point is characterized by the proliferation of topological defects that signal the emergence of Z2 gauge symmetry. PACS numbers: 71.27.+a, 71.28.+d, Frustrated magnets are the focus of considerable attention because exotic quantum effects are expected to emerge from the competition between two or more opposite tendencies. While several models in this category are solvable in one dimension, the list is much smaller for higher dimensions. One of the most studied frustrated magnets is the spin 1/2 Heisenberg model with first and second nearest neighbor interactions J 1 and J 2 . In one dimension, this model exhibits a quantum transition as a function of J 2 /J 1 from a critical state with quasi-long range antiferromagnetic (AF) order to a dimerized phase. Moreover, the exact dimerized ground state has been obtained for the point J 2 /J 1 = 0.5 by Majumdar and Ghosh [1]. In contrast, two dimensional (2D) frustrated magnets like the J 1 − J 2 Heisenberg model on a square lattice still hold many secrets. Different approaches predict a transition between a Néel ordered state and a gapped (non-magnetic) quantum phase for the region 0.4 J 2 /J 1 0.6. However, the nature of this phase is still debated. More precisely, the question is whether it is a uniform spin liquid [2, 3] or a spatially ordered valence bond crystal .
The intermediate valence compounds Yb 2 M 3 Ga 9 (M = Rh, Ir) exhibit an anisotropic magnetic sus... more The intermediate valence compounds Yb 2 M 3 Ga 9 (M = Rh, Ir) exhibit an anisotropic magnetic susceptibility. We report measurements of the temperature dependence of the 4f occupation number, n f (T), for Yb 2 M 3 Ga 9 as well as the magnetic inelastic neutron scattering spectrum S mag (∆E) at 12 and 300 K for Yb 2 Rh 3 Ga 9 . Both n f (T) and S mag (∆E) were calculated for the Anderson impurity model with crystal field terms within an approach based on the non-crossing approximation. These results corroborate the importance of crystal field effects in these materials; they also suggest that Anderson lattice effects are important to the physics of Yb 2 M 3 Ga 9 .
Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried... more Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried out on single crystals of the intermediate valence compounds Yb2Rh3Ga9 and Yb2Ir3Ga9. These measurements reveal a large anisotropy due apparently to an interplay between crystalline electric field (CEF) and Kondo effects. The temperature dependence of magnetic susceptibility can be modelled using the Anderson impurity model including CEF within an approach based on the Non-Crossing Approximation.
Goldenseal (Hydrastis canadensis L.) is a popular medicinal plant distributed widely in North Ame... more Goldenseal (Hydrastis canadensis L.) is a popular medicinal plant distributed widely in North America. The rhizome, rootlets, and root hairs produce medicinally active alkaloids. Berberine, one of the Hydrastis alkaloids, has shown antifungal activity. The influence of a combination of the major Hydrastis alkaloids on the plant rhizosphere fungal ecology has not been investigated. A bioassay was developed to study the effect of goldenseal isoquinoline alkaloids on three Fusarium isolates, including the two species isolated from Hydrastis rhizosphere. The findings suggest that the Hydrastis root extract influences macroconidia germination, but that only the combined alkaloids--berberine, canadine, and hydrastine--appear to synergistically stimulate production of the mycotoxin zearalenone in the Fusarium oxysporum isolate. The Hydrastis root rhizosphere effect provided a selective advantage to the Fusarium isolates closely associated with the root tissue in comparison with the Fusarium isolate that had never been exposed to Hydrastis.
We study numerically the one-dimensional ferromagnetic Kondo lattice model, which is widely used ... more We study numerically the one-dimensional ferromagnetic Kondo lattice model, which is widely used to describe nickel and manganese perovskites. We find broad regions near the commensurate dopings where the formation of magnetic polarons induces a charge-ordered state. This ordering arises from the competition between double and super-exchange, and is present even in the absence of any inter-site Coulomb repulsion. An
Coexisting low-energy scales are observed in f -electron materials. The information about some of... more Coexisting low-energy scales are observed in f -electron materials. The information about some of low-energy scales is imprinted in the electron self-energy, which can be measured by angle-resolved photoemission (ARPES). Such measurements in d-electron materials over the last decade were based on high energy-and momentumresolution ARPES techniques used to extract the self-energy information from measured spectra. Simultaneously, many-body theoretical approaches have been developed to find a link between the self-energy and many-body interactions. Here we show the transcription of such methods from d-electrons to f -electrons by presenting the first example of low energy scales in the f -electron material USb2, measured with synchrotron-based ARPES. The proposed approach will help in answering the fundamental questions about the complex nature of the heavy fermion state.
We report measurements of the specific heat of the quantum spin liquid system SrCu2(BO3)2 in cont... more We report measurements of the specific heat of the quantum spin liquid system SrCu2(BO3)2 in continuous magnetic fields H of up to 33 T. The specific heat data, when combined with a finite temperature Lanczos diagonalization of the Shastry-Sutherland Hamiltonian, indicates the presence of a nearest neighbor Dzyaloshinsky-Moriya (DM) interaction that violates the crystal symmetry for H = 0. Moreover, the same DM interaction is required to explain the observed ESR lines for H c. These results indicate that spin-lattice coupling needs to be included in any realistic description of this system.
We introduce a frustrated spin 1/2 Hamiltonian which is an extension of the two dimensional J1 −J... more We introduce a frustrated spin 1/2 Hamiltonian which is an extension of the two dimensional J1 −J2 Heisenberg model. The ground states of this model are exactly obtained at a first order quantum phase transition between two regions with different valence bond solid order parameters. At this point, the low energy excitations are deconfined spinons and spin-charge separation occurs under doping in the limit of low concentration of holes. In addition, this point is characterized by the proliferation of topological defects that signal the emergence of Z2 gauge symmetry. PACS numbers: 71.27.+a, 71.28.+d, Frustrated magnets are the focus of considerable attention because exotic quantum effects are expected to emerge from the competition between two or more opposite tendencies. While several models in this category are solvable in one dimension, the list is much smaller for higher dimensions. One of the most studied frustrated magnets is the spin 1/2 Heisenberg model with first and second nearest neighbor interactions J 1 and J 2 . In one dimension, this model exhibits a quantum transition as a function of J 2 /J 1 from a critical state with quasi-long range antiferromagnetic (AF) order to a dimerized phase. Moreover, the exact dimerized ground state has been obtained for the point J 2 /J 1 = 0.5 by Majumdar and Ghosh [1]. In contrast, two dimensional (2D) frustrated magnets like the J 1 − J 2 Heisenberg model on a square lattice still hold many secrets. Different approaches predict a transition between a Néel ordered state and a gapped (non-magnetic) quantum phase for the region 0.4 J 2 /J 1 0.6. However, the nature of this phase is still debated. More precisely, the question is whether it is a uniform spin liquid [2, 3] or a spatially ordered valence bond crystal .
The intermediate valence compounds Yb 2 M 3 Ga 9 (M = Rh, Ir) exhibit an anisotropic magnetic sus... more The intermediate valence compounds Yb 2 M 3 Ga 9 (M = Rh, Ir) exhibit an anisotropic magnetic susceptibility. We report measurements of the temperature dependence of the 4f occupation number, n f (T), for Yb 2 M 3 Ga 9 as well as the magnetic inelastic neutron scattering spectrum S mag (∆E) at 12 and 300 K for Yb 2 Rh 3 Ga 9 . Both n f (T) and S mag (∆E) were calculated for the Anderson impurity model with crystal field terms within an approach based on the non-crossing approximation. These results corroborate the importance of crystal field effects in these materials; they also suggest that Anderson lattice effects are important to the physics of Yb 2 M 3 Ga 9 .
Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried... more Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried out on single crystals of the intermediate valence compounds Yb2Rh3Ga9 and Yb2Ir3Ga9. These measurements reveal a large anisotropy due apparently to an interplay between crystalline electric field (CEF) and Kondo effects. The temperature dependence of magnetic susceptibility can be modelled using the Anderson impurity model including CEF within an approach based on the Non-Crossing Approximation.
Goldenseal (Hydrastis canadensis L.) is a popular medicinal plant distributed widely in North Ame... more Goldenseal (Hydrastis canadensis L.) is a popular medicinal plant distributed widely in North America. The rhizome, rootlets, and root hairs produce medicinally active alkaloids. Berberine, one of the Hydrastis alkaloids, has shown antifungal activity. The influence of a combination of the major Hydrastis alkaloids on the plant rhizosphere fungal ecology has not been investigated. A bioassay was developed to study the effect of goldenseal isoquinoline alkaloids on three Fusarium isolates, including the two species isolated from Hydrastis rhizosphere. The findings suggest that the Hydrastis root extract influences macroconidia germination, but that only the combined alkaloids--berberine, canadine, and hydrastine--appear to synergistically stimulate production of the mycotoxin zearalenone in the Fusarium oxysporum isolate. The Hydrastis root rhizosphere effect provided a selective advantage to the Fusarium isolates closely associated with the root tissue in comparison with the Fusarium isolate that had never been exposed to Hydrastis.
We study numerically the one-dimensional ferromagnetic Kondo lattice model, which is widely used ... more We study numerically the one-dimensional ferromagnetic Kondo lattice model, which is widely used to describe nickel and manganese perovskites. We find broad regions near the commensurate dopings where the formation of magnetic polarons induces a charge-ordered state. This ordering arises from the competition between double and super-exchange, and is present even in the absence of any inter-site Coulomb repulsion. An
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Papers by C. Batista