Chain-based order and quantum spin liquids in dipolar spin ice

Recent experiments on the spin-ice material Dy₂Ti₂O₇ suggest that the Pauling "ice entropy," characteristic of its classical Coulombic spin-liquid state, may be lost at low temperatures [Pomaranski, Nat. Phys. 9, 353 (2013)1745-247310.1038/nphys2591]. However, despite nearly two decades of intensive study, the nature of the equilibrium ground state of spin ice remains uncertain. Here we explore how long-range dipolar interactions D, short-range exchange interactions, and quantum fluctuations combine to determine the ground state of dipolar spin ice. We identify the organizational principle that ordered ground states are selected from a set of "chain states" in which dipolar interactions are exponentially screened. Using both quantum and classical Monte Carlo simulation, we establish phase diagrams as a function of quantum tunneling g and temperature T, and find that only a very small gcaD is needed to stabilize a quantum spin liquid ground state. We discuss the implications of these results for Dy₂Ti₂O₇.