@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},
}