Resonating valence bonds · no magnetic order · fractionalized excitations
A quantum spin liquid (QSL) is a state of matter where quantum fluctuations prevent magnetic ordering even at absolute zero. Anderson's resonating valence bond (RVB) picture (1973) describes the ground state as a superposition of all possible singlet-pair coverings of the lattice. This entangled state hosts fractionalized excitations: spinons (charge-neutral, spin-1/2 quasiparticles) and visons (flux excitations of an emergent Z₂ gauge field), which are deconfined and can move independently. Unlike conventional magnets, QSLs exhibit topological order and long-range entanglement invisible to local order parameters.