## Tunneling-induced restoration of classical degeneracy in quantum kagome ice

**Speaker:**Ying-Jer Kao, National Taiwan University and BU

**When:**December 12, 2018 (Wed), 03:00PM to 04:00PM (add to my calendar)

**Location:**SCI 328

**Hosted by:**Anders Sandvik

*This event is part of the Condensed Matter Theory Seminar Series. *

Quantum effect is expected to dictate the behavior of physical systems at low temperature. For quantum magnets with geometrical frustration, quantum fluctuation lifts the macroscopic classical degeneracy, and exotic quantum states emerge. However, how different types of quantum processes entangle wave functions in a constrained Hilbert space is not well understood. Here, we study the topological entanglement entropy and the thermal entropy of a quantum ice model on a geometrically frustrated kagome lattice. We find that the system does not show a Z_2 topological order down to extremely low temperatures, yet continues to behave like a classical kagome ice with finite residual entropy. Our theoretical analysis indicates that an intricate competition of off-diagonal and diagonal quantum tunneling processes leading to a suppression of the quantum energy scale.