Striped critical spin liquid in a spin-orbital entangled RVB state in a PEPS representation.

Piotr Czarnik, Jacek Dziarmaga

We introduce [1] a spin-orbital entangled (SOE) resonating valence bond (RVB) state on a square 
lattice of spins 1/2 and orbitals represented by pseudospins 1/2. Like the standard RVB state, it 
is a superposition of nearest-neighbor hard-core coverings of the lattice by spin singlets, but 
adjacent singlets are favored to have perpendicular orientations and, more importantly, an 
orientation of each singlet is entangled with orbitals state on its two lattice sites. The SOE-RVB 
state can be represented by a projected entangled pair state (PEPS) with a bond dimension D=4. This 
representation helps to reveal that the state is a superposition of striped coverings conserving a 
topological quantum number. The stripes are a critical quantum spin liquid. We propose spin-orbital 
Hamiltonians supporting a SOE-RVB ground state. 

[1] Piotr Czarnik, Jacek Dziarmaga; arXiv:1406.6841.