Characterizing random-singlet state in two-dimensional frustrated
quantum magnets and implications for the double perovskite
Sr2βCuTe1βxβWxβO6β
Motivated by experimental observation of the non-magnetic phase in the
compounds with frustration and disorder, we study the ground state of the
spin-1/2 square-lattice Heisenberg model with randomly distributed
nearest-neighbor J1β and next-nearest-neighbor J2β couplings. By using the
density matrix renormalization group (DMRG) calculation on cylinder system with
circumference up to 10 lattice sites, we identify a disordered phase between
the N\'eel and stripe magnetic phase with growing J2β/J1β in the presence
of strong randomness. The vanished spin-freezing parameter indicates the absent
spin glass order. The large-scale DMRG results unveil the size-scaling
behaviors of the spin-freezing parameter, the power-law decay of average spin
correlation, and the exponential decay of typical spin correlation, which all
agree with the corresponding behavior in the one-dimensional random singlet
(RS) state and characterize the RS nature of this non-magnetic state. The DMRG
simulation also opens new insight and opportunities for characterizing a class
of non-magnetic states in two-dimensional frustrated magnets with disorder. We
also compare with existing experiments and suggest more measurements for
understanding the spin-liquid-like behavior in the double perovskite
Sr2βCuTe1βxβWxβO6β.Comment: 11 pages,10 figure