Junior Research Chair
Department of Physics, Ecole Normale Superieure, Paris
Magnetic monopoles in quantum spin ice
The quest for quantum spin liquids is an important enterprise in strongly correlated physics, yet candidate materials are still few and far between. Meanwhile, the classical front has had far more success, epitomized by the exceptional agreement between theory and experiment for a class of materials called spin ices. It is therefore natural to introduce quantum fluctuations into this well-established classical spin liquid model, in the hopes of obtaining a fully quantum spin liquid state.
In the more general, unperturbed case we find that the classical degeneracy of the excited states is only partially lifted by quantum fluctuations in the form of a transverse field term. I will discuss a family of extensively degenerate excited states that make up an approximately flat band at the first excited classical energy level. These states are exact up to the splitting of the spin ice ground state manifold.