Thermodynamics of Adiabatically Loaded Cold Bosons in the Mott Insulating Phase of One-Dimensional Optical Lattices

In this work we give a consistent picture of the thermodynamic properties of bosons in the Mott insulating phase when loaded adiabatically into one-dimensional optical lattices. We find a crucial dependence of the temperature in the optical lattice on the doping level of the Mott insulator. In the undoped case, the temperature is of the order of the large onsite Hubbard interaction. In contrast, at a finite doping level the temperature jumps almost immediately to the order of the small hopping parameter. These two situations are investigated on the one hand by considering limiting cases like the atomic limit and the case of free fermions. On the other hand, they are examined using a quasi-particle conserving continuous unitary transformation extended by an approximate thermodynamics for hardcore particles.Comment: 10 pages, 6 figure

Temperature in One-Dimensional Bosonic Mott insulators

The Mott insulating phase of a one-dimensional bosonic gas trapped in optical lattices is described by a Bose-Hubbard model. A continuous unitary transformation is used to map this model onto an effective model conserving the number of elementary excitations. We obtain quantitative results for the kinetics and for the spectral weights of the low-energy excitations for a broad range of parameters in the insulating phase. By these results, recent Bragg spectroscopy experiments are explained. Evidence for a significant temperature of the order of the microscopic energy scales is found.Comment: 8 pages, 7 figure

Liquid Water and Interfacial, Cubic, and Hexagonal Ice Classification through Eclipsed and Staggered Conformation Template Matching

We propose a novel method based on template matching for the recognition of liquid water, cubic ice (ice Ic), hexagonal ice (ice Ih), clathrate hydrates, and different interfacial structures in atomistic and coarse-grained simulations of water and ice. The two template matrices represent staggered and eclipsed conformations, which are the building blocks of hexagonal and cubic ice and clathrate crystals. The algorithm is rotationally invariant and highly robust against imperfections in the ice structure, and its sensitivity for recognizing ice-like structures can be tuned for different applications. Unlike most other algorithms, it can discriminate between cubic, hexagonal, clathrate, mixed, and other interfacial ice types and is therefore well suited to study complex systems and heterogeneous ice nucleation.Peer reviewe

Systematic Mapping of the Hubbard Model to the Generalized t-J Model

The generalized t-J model conserving the number of double occupancies is constructed from the Hubbard model at and in the vicinity of half-filling at strong coupling. The construction is realized by a self-similar continuous unitary transformation. The flow equation is closed by a truncation scheme based on the spatial range of processes. We analyze the conditions under which the t-J model can be set up and we find that it can only be defined for sufficiently large interaction. There, the parameters of the effective model are determined.Comment: 16 pages, 13 figures included. v2: Order of sections changed. Calculation and discussion of apparent gap in Section IV.A correcte

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Sufficiently dimerized quantum antiferromagnets display elementary S=1 excitations, triplon quasiparticles, protected by a gap at low energies. At higher energies, the triplons may decay into two or more triplons. A strong enough magnetic field induces Bose-Einstein condensation of triplons. For both phenomena the compound IPA-CuCl3 is an excellent model system. Nevertheless no quantitative model was determined so far despite numerous studies. Recent theoretical progress allows us to analyse data of inelastic neutron scattering (INS) and of magnetic susceptibility to determine the four magnetic couplings J1=-2.3meV, J2=1.2meV, J3=2.9meV and J4=-0.3meV. These couplings determine IPA-CuCl3 as system of coupled asymmetric S=1/2 Heisenberg ladders quantitatively. The magnetic field dependence of the lowest modes in the condensed phase as well as the temperature dependence of the gap without magnetic field corroborate this microscopic model.Comment: 6 pages, 5 figure

Imaging of tumor hypoxia with [124I]IAZA in comparison with [18F]FMISO and [18F]FAZA – first small animal PET results

PURPOSE: This study was performed to compare the 2-nitroimidazole derivatives [124I]IAZA, [18F]FAZA and well known [18F]FMISO in visualization of tumor hypoxia in a mouse model of human cancer using small animal PET. METHODS: PET imaging of female Balb/c nude mice bearing A431 tumors on a Phillips Mosaic small animal PET scanner was performed 3 h p.i. for all three tracers. Mice injected with [124I]IAZA were scanned again after 24 h and 48 h. In addition to the mice breathing air, in the case of [18F]FAZA and [124I]IAZA a second group of mice for each tracer was kept in an atmosphere of carbogen gas (5% of CO2 + 95 % of O2; from 1 h before to 3 h after injection) to evaluate the oxygenation dependency on uptake (all experiments n = 4). After the final PET scan animals were sacrificed and biodistribution was studied. RESULTS: Mice injected with [18F]FAZA displayed significantly higher tumor-to background (T/B) ratios (5.19 +/- 0.73) compared to those injected with [18F]FMISO (3.98 +/- 0.66; P $lt; 0.05) or [124I]IAZA (2.06 +/- 0.26; P$lt; 0.001) 3 h p.i. Carbogen breathing mice showed lower ratios ([18F]FAZA: 4.06 +/- 0.59; [124I]IAZA: 2.02 +/- 0.36). The T/B ratios increased for [124I]IAZA with time (24 h: 3.83 +/- 0.61; 48 h: 4.20 +/- 0.80), but after these late time points the absolute whole body activity was very low, as could be seen from the biodistribution data (< 0.1 %ID/g for each investigated organ) and ratios were still lower than for [18F]FAZA 3 h p.i. Due to de-iodination uptake in thyroid was high. Biodistribution data were in good agreement with the PET results. CONCLUSIONS: [18F]FAZA showed superior biokinetics compared to [18F]FMISO and [124I]IAZA in this study. Imaging at later time points that are not possible with the short lived 18F labeled tracers resulted in no advantage for [124I]IAZA, i. e. tumor to normal tissue ratios could not be improved. © 1999 Canadian Society for Pharmaceutical Sciences