Date：Monday 29th May 2017 10:30 - 11:30am
Place：Main building Seminar room A615
Lecturer : Nicholas Shannon（Okinawa Institute for Science and Technology）

Title：Quantum Water Ice

Abstract：

Water is one of the most ubiquitous substances on earth, but also one of the strangest.  For example, common, hexagonal water-ice is not really a crystal by any conventional definition, but rather an ordered lattice of oxygen ions, held together by a disordered network of hydrogren bonds.

There is now a growing body of evidence, from both experiment [1] and simulation [2], that the protons in hexagonal water ice are not merely disordered, but mobile, collectively tunneling from one configuration obeying the Bernal-Fowler “ice rules” to another.  However, despite

enormous progress in understanding related quantum effects in magnets, very little is known about what effect such collective quantum tunneling might have on the protons in water ice.

In this talk we revisit the theory of proton correlations in hexagonal water ice, showing how the disordered state selected by the ice rules changes, once collective quantum tunneling is taken into account.  We find that quantum tunneling can give rise to a novel quantum liquid state, involving the superposition of an extensive number of different proton configurations, with entanglement over macroscopic length scales [3].  This state shares many of the same properties as the quantum spin liquids sought in frustrated magnets.

References :

[1] L, Bove et al., Phys. Rev. Lett. 103, 165901 (2009)

[2] C. Drechsel-Grau and D. Marx, Phys. Rev. Lett. 112, 148302 (2014)

[3] O. Benton et al., Phys. Rev. B 93, 125143 (2016)