Exotic gapless spectrum induced by frustration in quantum antiferromagnets

Federico Becca, Luca Capriotti, Alberto Parola, Sandro Sorella
2007 Physical Review B  
We show strong numerical evidence in favor of an unexpected virtually gapless spectrum, with edge states localized at the boundaries, in frustrated spin-1/2 antiferromagnetic ladders with an odd number of legs. These features can be accurately reproduced by using a projected BCS wave function with a non-trivial pairing, that mixes even and odd reflection symmetries. This approach gives the correct classification of the excitations and provides a simple and very appealing picture of an unconventional spin-liquid phase stabilized by frustration.
doi:10.1103/physrevb.76.060401 fatcat:tjbrmzxcsbeznjutzoihjznjvu