S=1 spin liquid with fermionic excitations

In the first part of my talk I describe a search for
possible quantum spin liquid ground states for spin S=1 Heisenberg models on
the triangular lattice which was motivated by recent experiments on
Ba3NiSb2O9.  We use representation of
spin-1 via three flavors of fermionic spinon operators. The ground state where
one gapless flavor of spinons with a Fermi surface coexists with d+id
topological pairing of the two other flavors can explain available experimental
data. Despite the existence of a Fermi surface, this spin liquid state has
fully gapped bulk spin excitations. This results in a linear in-temperature
specific heat and constant in-plane spin susceptibility, with an unusually high
Wilson ratio. Using variational Monte Carlo technique, we show that proposed
spin liquid ground state is realized in an SU(3)-invariant model with
sufficiently strong ring-exchange terms.

 

In the second part, I consider the physics of the
magnetic s=1/2 impurity embedded in a S=1 spin liquid, where all three flavors of
spinons have a Fermi surface. The interplay between non-Fermi-liquid behavior
induced by a U(1) gauge field coupled to fermions, and a non-Fermi-liquid fixed
point in the overscreened Kondo problem is studied using double expansion. The
gauge field changes the physical properties of the system at the overscreened
Kondo fixed point. Thus, spin-half impurity in such spin liquid can be used to
probe the presence of fermionic spinons coupled to the gauge field.

 

References: arXiv:1108.3070, arXiv:1208.3231 and
arXiv:1212.5179

Event Type: 
Seminar
Collection/Series: 
Scientific Area(s): 
Speaker(s): 
Event Date: 
Jeudi, Mars 28, 2013 - 14:30 to 16:00
Location: 
Bob Room