"Exploring the spin-orbital ground state of Ba3CuSb2O9" Andrew Smerald

Seminar Information :

Thoery of Quantum Matter Unit would like to invite you to a seminar:

• Title: "Exploring the spin-orbital ground state of Ba3CuSb2O9"
• Speaker: Dr. Andrew Smerald, EPFL Lausanne
• Date/Time: Mon, 23rd June / 11:00-12:00
• Venue: C016, Lab1

"Exploring the spin-orbital ground state of Ba3CuSb2O9"

Andrew Smerald, EPFL Lausanne

The interplay of spin and orbital degrees of freedom often leads to frustration, and can give rise to unusual quantum ground states. In this talk we consider the ground state of the Mott insulator Ba3CuSb2O9, motivated by the absence of both spin freezing and orbital order at the lowest measured temperatures. We solve a spin-orbital Hamiltonian on the honeycomb and decorated honeycomb lattices, revealing rich phase diagrams, which include phases controlled by an SU(4) symmetric point. For realistic parameters on the decorated honeycomb lattice, we find a phase that consists of clusters of nearest-neighbour spin singlets, which can be understood in terms of dimer coverings of an emergent square lattice. While the experimental situation is complicated by structural disorder, we show qualitative agreement between our theory and a range of experiments."