A Supercooled Spin Liquid State in the Frustrated Pyrochlore Dy2Ti2O7

A "supercooled" liquid develops when a fluid does not crystallize upon cooling below its ordering temperature. Instead, the microscopic relaxation times diverge so rapidly that, upon further cooling, equilibration eventually becomes impossible and glass formation occurs. Classic supercooled liquids exhibit specific identifiers including microscopic relaxation times diverging on a Vogel-Tammann-Fulcher (VTF) trajectory, a Havriliak-Negami (HN) form for the dielectric function, and a general Kohlrausch-Williams-Watts (KWW) form for time-domain relaxation. Recently, the pyrochlore Dy2Ti2O7 has become of interest because its frustrated magnetic interactions may, in theory, lead to highly exotic magnetic fluids. However, its true magnetic state at low temperatures has proven very difficult to identify unambiguously. Here we introduce high-precision, boundary-free magnetization transport techniques based upon toroidal geometries and gain a fundamentally new understanding of the time- and frequency-dependent magnetization dynamics of Dy2Ti2O7. We demonstrate a virtually universal HN form for the magnetic susceptibility, a general KWW form for the real-time magnetic relaxation, and a divergence of the microscopic magnetic relaxation rates with precisely the VTF trajectory. Low temperature Dy2Ti2O7 therefore exhibits the characteristics of a supercooled magnetic liquid; the consequent implication is that this translationally invariant lattice of strongly correlated spins is evolving towards an unprecedented magnetic glass state, perhaps due to many-body localization of spin.Comment: Version 2 updates: added legend for data in Figures 4A and 4B; corrected equation reference in caption for Figure 4

Developing a Reflexive, Anticipatory, and Deliberative Approach to Unanticipated Discoveries: Ethical Lessons from iBlastoids

In this paper, we explore the recent creation of “iBlastoids,” which are 3-D structures that resemble early human embryos prior to implantation which formed via self-organization of reprogrammed adult skin cells. We explore some of the ethical, philosophical, social, and regulatory issues related to this research, with focus particularly on what it means to “anticipate” research outcomes when using novel methods or when serendipitous discoveries are made. We defend the need for reflexive, anticipatory, and deliberative ethical and conceptual work by researchers working in emerging and contentious research domains, in collaboration with interdisciplinary scholars, as well as regulators, funders, and publics.Rachel A. Ankeny, Megan J. Munsie and Joan Leac