@article{7078,
abstract = {We report resonant ultrasound spectroscopy (RUS), dilatometry/magnetostriction, magnetotransport, magnetization, specific-heat, and 119Sn Mössbauer spectroscopy measurements on SnTe and Sn0.995Cr0.005Te. Hall measurements at T=77 K indicate that our Bridgman-grown single crystals have a p-type carrier concentration of 3.4×1019 cm−3 and that our Cr-doped crystals have an n-type concentration of 5.8×1022 cm−3. Although our SnTe crystals are diamagnetic over the temperature range 2≤T≤1100 K, the Cr-doped crystals are room-temperature ferromagnets with a Curie temperature of 294 K. For each sample type, three-terminal capacitive dilatometry measurements detect a subtle 0.5 μm distortion at Tc≈85 K. Whereas our RUS measurements on SnTe show elastic hardening near the structural transition, pointing to co-elastic behavior, similar measurements on Sn0.995Cr0.005Te show a pronounced softening, pointing to ferroelastic behavior. Effective Debye temperature, θD, values of SnTe obtained from 119Sn Mössbauer studies show a hardening of phonons in the range 60–115 K (θD=162 K) as compared with the 100–300 K range (θD=150 K). In addition, a precursor softening extending over approximately 100 K anticipates this collapse at the critical temperature and quantitative analysis over three decades of its reduced modulus finds ΔC44/C44=A|(T−T0)/T0|−κ with κ=0.50±0.02, a value indicating a three-dimensional softening of phonon branches at a temperature T0∼75 K, considerably below Tc. We suggest that the differences in these two types of elastic behaviors lie in the absence of elastic domain-wall motion in the one case and their nucleation in the other.},
author = {Salje, E. K. H. and Safarik, D. J. and Modic, Kimberly A and Gubernatis, J. E. and Cooley, J. C. and Taylor, R. D. and Mihaila, B. and Saxena, A. and Lookman, T. and Smith, J. L. and Fisher, R. A. and Pasternak, M. and Opeil, C. P. and Siegrist, T. and Littlewood, P. B. and Lashley, J. C.},
issn = {1098-0121},
journal = {Physical Review B},
number = {18},
publisher = {APS},
title = {{Tin telluride: A weakly co-elastic metal}},
doi = {10.1103/physrevb.82.184112},
volume = {82},
year = {2010},
}
@article{1465,
abstract = {We prove a generating function formula for the Betti numbers of Nakajima quiver varieties. We prove that it is a q-deformation of the Weyl-Kac character formula. In particular this implies that the constant term of the polynomial counting the number of absolutely indecomposable representations of a quiver equals the multiplicity of a certain weight in the corresponding Kac-Moody algebra, which was conjectured by Kac in 1982.},
author = {Tamas Hausel},
journal = {Inventiones Mathematicae},
number = {1},
pages = {21 -- 37},
publisher = {Springer},
title = {{Kac's conjecture from Nakajima quiver varieties}},
doi = {10.1007/s00222-010-0241-3},
volume = {181},
year = {2010},
}
@article{1466,
abstract = {In Hausel et al. (2008) [10] we presented a conjecture generalizing the Cauchy formula for Macdonald polynomial. This conjecture encodes the mixed Hodge polynomials of the character varieties of representations of the fundamental group of a punctured Riemann surface of genus g. We proved several results which support this conjecture. Here we announce new results which are consequences of those in Hausel et al. (2008) [10].},
author = {Tamas Hausel and Letellier, Emmanuel and Rodríguez Villegas, Fernando},
journal = {Comptes Rendus Mathematique},
number = {3-4},
pages = {131 -- 135},
publisher = {Elsevier},
title = {{Topology of character varieties and representations of quivers}},
doi = {10.1016/j.crma.2010.01.025},
volume = {348},
year = {2010},
}
@inbook{1468,
abstract = {This chapter surveys the motivations, related results, and progress made towards the following problem, raised by Hitchin in 1995: What is the space of L2 harmonic forms on the moduli space of Higgs bundles on a Riemann surface?},
author = {Tamas Hausel},
booktitle = {The Many Facets of Geometry: A Tribute to Nigel Hitchin},
publisher = {Oxford University Press},
title = {{S-Duality in HyperkäHler Hodge Theory}},
doi = {10.1093/acprof:oso/9780199534920.003.0016},
year = {2010},
}
@article{1044,
abstract = {Control over all internal and external degrees of freedom of molecules at the level of single quantum states will enable a series of fundamental studies in physics and chemistry1,2. In particular, samples of ground-state molecules at ultralow temperatures and high number densities will facilitate new quantum-gas studies3 and future applications in quantum information science4. However, high phase-space densities for molecular samples are not readily attainable because efficient cooling techniques such as laser cooling are lacking. Here we produce an ultracold and dense sample of molecules in a single hyperfine level of the rovibronic ground state with each molecule individually trapped in the motional ground state of an optical lattice well. Starting from a zero-temperature atomic Mott-insulator state with optimized double-site occupancy6, weakly bound dimer molecules are efficiently associated on a Feshbach resonance7 and subsequently transferred to the rovibronic ground state by a stimulated four-photon process with >50% efficiency. The molecules are trapped in the lattice and have a lifetime of 8 s. Our results present a crucial step towards Bose-Einstein condensation of ground-state molecules and, when suitably generalized to polar heteronuclear molecules, the realization of dipolar quantum-gas phases in optical lattices8-10.},
author = {Danzl, Johann G and Mark, Manfred and Haller, Elmar and Gustavsson, Mattias and Hart, Russell and Aldegunde, Jesus and Hutson, Jeremy and Nägerl, Hanns},
journal = {Nature Physics},
number = {4},
pages = {265 -- 270},
publisher = {Nature Publishing Group},
title = {{An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice}},
doi = {10.1038/nphys1533},
volume = {6},
year = {2010},
}
@article{1045,
abstract = {We report on the observation of confinement-induced resonances in strongly interacting quantum-gas systems with tunable interactions for one- and two-dimensional geometry. Atom-atom scattering is substantially modified when the s-wave scattering length approaches the length scale associated with the tight transversal confinement, leading to characteristic loss and heating signatures. Upon introducing an anisotropy for the transversal confinement we observe a splitting of the confinement-induced resonance. With increasing anisotropy additional resonances appear. In the limit of a two-dimensional system we find that one resonance persists.},
author = {Haller, Elmar and Mark, Manfred and Hart, Russell and Danzl, Johann G and Reichsöllner, Lukas and Melezhik, Vladimir and Schmelcher, Peter and Nägerl, Hanns},
journal = {Physical Review Letters},
number = {15},
publisher = {American Physical Society},
title = {{Confinement-induced resonances in low-dimensional quantum systems}},
doi = {10.1103/PhysRevLett.104.153203},
volume = {104},
year = {2010},
}
@article{1047,
abstract = {Particles in a perfect lattice potential perform Bloch oscillations when subject to a constant force, leading to localization and preventing conductivity. For a weakly interacting Bose-Einstein condensate of Cs atoms, we observe giant center-of-mass oscillations in position space with a displacement across hundreds of lattice sites when we add a periodic modulation to the force near the Bloch frequency. We study the dependence of these "super" Bloch oscillations on lattice depth, modulation amplitude, and modulation frequency and show that they provide a means to induce linear transport in a dissipation-free lattice.},
author = {Haller, Elmar and Hart, Russell and Mark, Manfred and Danzl, Johann G and Reichsöllner, Lukas and Nägerl, Hanns},
journal = {Physical Review Letters},
number = {20},
publisher = {American Physical Society},
title = {{Inducing transport in a dissipation-free lattice with super bloch oscillations}},
doi = {10.1103/PhysRevLett.104.200403},
volume = {104},
year = {2010},
}
@article{1049,
abstract = {Quantum many-body systems can have phase transitions even at zero temperature; fluctuations arising from Heisenbergĝ€™s uncertainty principle, as opposed to thermal effects, drive the system from one phase to another. Typically, during the transition the relative strength of two competing terms in the systemĝ€™s Hamiltonian changes across a finite critical value. A well-known example is the Mottĝ€" Hubbard quantum phase transition from a superfluid to an insulating phase, which has been observed for weakly interacting bosonic atomic gases. However, for strongly interacting quantum systems confined to lower-dimensional geometry, a novel type of quantum phase transition may be induced and driven by an arbitrarily weak perturbation to the Hamiltonian. Here we observe such an effectĝ€"the sineĝ€"Gordon quantum phase transition from a superfluid Luttinger liquid to a Mott insulatorĝ€ "in a one-dimensional quantum gas of bosonic caesium atoms with tunable interactions. For sufficiently strong interactions, the transition is induced by adding an arbitrarily weak optical lattice commensurate with the atomic granularity, which leads to immediate pinning of the atoms. We map out the phase diagram and find that our measurements in the strongly interacting regime agree well with a quantum field description based on the exactly solvable sineĝ€"Gordon model. We trace the phase boundary all the way to the weakly interacting regime, where we find good agreement with the predictions of the one-dimensional Boseĝ€"Hubbard model. Our results open up the experimental study of quantum phase transitions, criticality and transport phenomena beyond Hubbard-type models in the context of ultracold gases.},
author = {Haller, Elmar and Hart, Russell and Mark, Manfred and Danzl, Johann G and Reichsöllner, Lukas and Gustavsson, Mattias and Dalmonte, Marcello and Pupillo, Guido and Nägerl, Hanns},
journal = {Nature},
number = {7306},
pages = {597 -- 600},
publisher = {Nature Publishing Group},
title = {{Pinning quantum phase transition for a Luttinger liquid of strongly interacting bosons}},
doi = {10.1038/nature09259},
volume = {466},
year = {2010},
}
@article{9012,
abstract = {In this Letter, we characterize experimentally the diffusiophoretic motion of colloids and λ-DNA toward higher concentration of solutes, using microfluidic technology to build spatially and temporally controlled concentration gradients. We then demonstrate that segregation and spatial patterning of the particles can be achieved from temporal variations of the solute concentration profile. This segregation takes the form of a strong trapping potential, stemming from an osmotically induced rectification mechanism of the solute time-dependent variations. Depending on the spatial and temporal symmetry of the solute signal, localization patterns with various shapes can be achieved. These results highlight the role of solute contrasts in out-of-equilibrium processes occurring in soft matter.},
author = {Palacci, Jérémie A and Abécassis, Benjamin and Cottin-Bizonne, Cécile and Ybert, Christophe and Bocquet, Lydéric},
issn = {10797114},
journal = {Physical Review Letters},
number = {13},
publisher = {American Physical Society},
title = {{Colloidal motility and pattern formation under rectified diffusiophoresis}},
doi = {10.1103/physrevlett.104.138302},
volume = {104},
year = {2010},
}
@article{9013,
abstract = {In this Letter, we investigate experimentally the nonequilibrium steady state of an active colloidal suspension under gravity field. The active particles are made of chemically powered colloids, showing self propulsion in the presence of an added fuel, here hydrogen peroxide. The active suspension is studied in a dedicated microfluidic device, made of permeable gel microstructures. Both the microdynamics of individual colloids and the global stationary state of the suspension under gravity are measured with optical microscopy. This yields a direct measurement of the effective temperature of the active system as a function of the particle activity, on the basis of the fluctuation-dissipation relationship. Our work is a first step in the experimental exploration of the out-of-equilibrium properties of active colloidal systems.},
author = {Palacci, Jérémie A and Cottin-Bizonne, Cécile and Ybert, Christophe and Bocquet, Lydéric},
issn = {10797114},
journal = {Physical Review Letters},
number = {8},
publisher = {American Physical Society },
title = {{Sedimentation and effective temperature of active colloidal suspensions}},
doi = {10.1103/physrevlett.105.088304},
volume = {105},
year = {2010},
}