We report a structural and thermodynamic study of the "stuffed spin ice" material Ho2TiO5 (i.e., Ho2(Ti1.33Ho0.67)O6.67), comparing samples synthesized through two different routes. Neutron powder diffraction and electron diffraction reveal that the previously reported defect fluorite phase has short-range pyrochlore ordering, in that there are domains in which the Ho and Ho/Ti sublattices are distinct. By contrast, a sample prepared through a floating zone method has long range ordering of these sublattices. Despite the differences in crystal structures, the two versions of Ho2TiO5 display similar magnetic susceptibilities. Field dependent magnetization and measured recovered entropies, however, show a difference between the two forms, suggesting that the magnetic properties of the stuffed pyrochlores depend on the local structure.

G. C. Lau B. G. Ueland M. L. Dahlberg R. S. Freitas Q. Huang H. W. Zandbergen P. Schiffer R. J. Cava

The magnetic moment of a single impurity atom in a finite free electron gas is studied in a combined x-ray magnetic circular dichroism spectroscopy and density functional theory study of size-selected free chromium-doped gold clusters. The observed size-dependence of the local magnetic moment can essentially be understood in terms of the Anderson impurity model. Electronic shell closure in the host metal minimizes the interaction of localized impurity states with the confined free electron gas and preserves the full magnetic moment of $\unit[5]{\mu_B}$ in $\mathrm{CrAu}_{2}^{+}$ and $\mathrm{CrAu}_{6}^{+}$ clusters. Even for open-shell species, large local moments are observed that scale with the energy gap of the gold cluster. This indicates that an energy gap in the free electron gas generally stabilizes the local magnetic moment of the impurity.

K. Hirsch V. Zamudio-Bayer A. Langenberg M. Niemeyer B. Langbehn T. Möller A. Terasaki B. v. Issendorff J. T. Lau

Microarcsecond resolutions afforded by an optical-NIR array with kilometer-baselines would enable breakthrough science. However significant technology barriers exist in transporting weakly coherent photon states over these distances: primarily photon loss and phase errors. Quantum telescopy, using entangled states to link spatially separated apertures, offers a possible solution to the loss of photons. We report on an initiative launched by NSF NOIRLab in collaboration with the Center for Quantum Networks and Arizona Quantum Initiative at the University of Arizona, Tucson, to explore these concepts further. A brief description of the quantum concepts and a possible technology roadmap towards a quantum-enhanced very long baseline optical-NIR interferometric array is presented. An on-sky demonstration of measuring spatial coherence of photons with apertures linked through the simplest Gottesman protocol over short baselines and with limited phase fluctuations is envisaged as the first step.

Jayadev K. Rajagopal Ryan M. Lau Isack Padilla Stephen T. Ridgway Chaohan Cui Brittany McClinton Aqil Sajjad Stuartt Corder Mark Rawlings Fredrik Rantakyro J. Gabriel Richardson Amit Ashok Saikat Guha

The Atacama Cosmology Telescope is a 6-meter telescope designed to map the Cosmic Microwave Background simultaneously at 145 GHz, 215 GHz, and 280 GHz with arcminute resolution. Each frequency will have a 32 by 32 element focal plane array of TES bolometers. This paper describes the design of the telescope and the cold reimaging optics, which is optimized for millimeter-wave observations with these sensitive detectors.

J. W. Fowler M. D. Niemack S. R. Dicker A. M. Aboobaker P. A. R. Ade E. S. Battistelli M. J. Devlin R. P. Fisher M. Halpern P. C. Hargrave A. D. Hincks M. Kaul J. Klein J. M. Lau M. Limon T. A. Marriage P. D. Mauskopf L. Page S. T. Staggs D. S. Swetz E. R. Switzer R. J. Thornton C. E. Tucker

Several shielding applications, to protect human health and electronic devices against dangerous effects of electromagnetic radiation, require solutions that fabrics can suitably fulfill. Here, we will investigate the electromagnetic interference shielding effectiveness of polypyrrole-coated polyester textiles, in the frequency range 100-1000 MHz. Insertion losses for several conductive fabrics with different surface resistivity ranging from 40 Ohm till the very low value of 3 Ohm were evaluated with a dual-tem cell. Correlations between the shielding effectiveness and the conductivity of composites are also discussed.

J. Avloni L. Florio A. R. Henn R. Lau M. Ouyang A. Sparavigna

We demonstrate a near-field Talbot-Lau interferometer for C-70 fullerene molecules. Such interferometers are particularly suitable for larger masses. Using three free-standing gold gratings of one micrometer period and a transversally incoherent but velocity-selected molecular beam, we achieve an interference fringe visibility of 40 % with high count rate. Both the high visibility and its velocity dependence are in good agreement with a quantum simulation that takes into account the van der Waals interaction of the molecules with the gratings and are in striking contrast to a classical moire model.

B. Brezger L. Hackermüller S. Uttenthaler J. Petschinka M. Arndt A. Zeilinger

The magnetic susceptibilities and specific heats of the crystalline garnet and glass forms of Mn3Al2Si3O12 are reported. This allows a direct comparison of the degree of magnetic frustration of the triangle-based garnet lattice and the structurally disordered solid at the same composition for isotropic spin 5/2 Mn^2+ (3d^5). The results show that the glass phase shows more pronounced signs of magnetic frustration than the crystalline phase. Through comparison of the specific heats of Ca3Al2Si3O12 (grossular) and Mn3Al2Si3O12 (spessartine) garnets, information is provided concerning the anomalous extra specific heat in the latter material.

G. C. Lau T. Klimczuk F. Ronning T. M. McQueen R. J. Cava

In this paper we study fixed point properties for semitopological semigroup of nonexpansive mappings on a bounded closed convex subset of a Banach space. We also study a Schauder fixed point property for a semitopological semigroup of continuous mappings on a compact convex subset of a separated locally convex space. Such semigroups properly include the class of extremely left amenable semitopological semigroups, the free commutative semigroup on one generator and the bicyclic semigroup $S_1 = < a, b: ab = 1 >$.

A. T. -M. Lau Yong Zhang

Cavity-enhanced single photon sources exhibit mode-locked biphoton states with comb-like correlation functions. Our ultrabright source additionally emits either single photon pairs or two-photon NOON states, dividing the output into an even and an odd comb respectively. With even-comb photons we demonstrate revivals of the typical non-classical Hong-Ou-Mandel interference up to the 84th dip, corresponding to a path length difference exceeding 100 m. With odd-comb photons we observe single photon interference fringes modulated over twice the displacement range of the Hong-Ou-Mandel interference.

Markus Rambach W. Y. Sarah Lau Simon Laibacher Vincenzo Tamma Andrew G. White Till J. Weinhold

In this paper, we deal with cohomological properties of weak amenability, cyclic amenability, cyclic weak amenability and point amenability of Banach algebras. We look at some hereditary properties of them and show that continuous homomorphisms with dense range preserve cyclically weak amenability, however, weak amenability and cyclically amenability are preserved under certain conditions. We also study these cohomological properties of the $\theta-$Lau product $A\times_\theta B$ and the projective tensor product $A\hat{\otimes} B$. Finally, we investigate the cohomological properties of $A^{**}$ and establish that cyclically weak amenability of $A^{**}$ implies cyclically weak amenability of $A$. This result is true for point amenability instead of cyclically weak amenability.

M. J. Mehdipour A. Rejali