Evidence for a three-dimensional quantum spin liquid in PbCuTe2O6

Abstract

The quantum spin liquid is a highly entangled magnetic state characterized by the absence of static magnetism in its ground state. Instead, the spins fluctuate in a highly correlated way down to the lowest temperatures. Quantum spin liquids are very rare and are confined to a few specific cases where the interactions between the magnetic ions cannot be simultaneously satisfied (known as frustration). Lattices with magnetic ions in triangular or tetrahedral arrangements, which interact via isotropic antiferromagnetic interactions, can generate such a frustration. Three-dimensional isotropic spin liquids have mostly been sought in materials where the magnetic ions form pyrochlore or hyperkagome lattices. Here we present a three-dimensional lattice called the hyper-hyperkagome that enables spin liquid behaviour and manifests in the compound PbCuTe 2 O 6. Using a combination of experiment and theory, we show that this system exhibits signs of being a quantum spin liquid with no detectable static magnetism together with the presence of diffuse continua in the magnetic spectrum suggestive of fractional spinon excitations.

Magnetic structure of the quantum magnet SrCuTe2O6

“…This observation is clearly in contrast to the strong frustration observed in PbCuTe 2 O 6 due to the hyper-hyperkagome interactions (where the J 1 and J 2 interactions are dominant, antiferromagnetic and of equal strength) [12] despite the structural similarity. However, some differences between these two compounds still remain in the form of bond angles responsible for the superexchange pathways as proposed by Koteswararao et al [16].…”

“…PbCuTe 2 O 6 is an example of a highly connected hyperkagome lattice, also known as the hyper-hyperkagome lattice, formed by the highly frustrated first-and secondnearest neighbor (NN) interactions between Cu 2+ spins [12]. Experimental and theoretical studies of this compound reveal evidence for quantum spin liquid behavior down to 20 mK, a rare observation in three-dimensional magnetic lattices [12][13][14], confirming the strong frustration in the system. However, density-functional theory calculations also suggest significant nonfrustrated third-and fourth-NN magnetic interactions in PbCuTe 2 O 6 whose role in the QSL phase diagram is less understood.…”

Structural and magnetic properties of the quantum magnet BaCuTe2O6

“…Recently a family of quantum magnets with chemical formula ACuTe 2 O 6 (A = Sr, Pb) was reported [15][16][17][18][19][20][21][22]. These compounds have cubic space group P4 1 32 where the magnetic Cu 2+ ions (S = 1/2) occupy the 12d Wyckoff site.…”

Spin-liquid behavior of the three-dimensional magnetic system Ba3NiIr2O9 with S=1

“…Over the past 15 years, several spin-1/2 systems with twodimensional (2D) frustrated lattice have been reported as probable candidates with QSL behavior [2][3][4][5][6]. Since experimental reports of QSL with either spin (S) 1 [7,8] or 3D arrangement of spins [9][10][11][12][13] are very few, it can be easily anticipated that chances of having a QSL with both higher spin and 3D geometry is extremely low [14]. Many of the attempts to obtain spin-1 QSL have been focused on stabilizing Ni within various structural networks [7,8,[14][15][16][17].…”

“…If both Ni and Ir moments of Ba 3 NiIr 2 O 9 (BNIO) fluctuate dynamically, then it would offer a new route to realize 3D QSL by involving two different magnetic ions. Also, it would be a 3D QSL with a new type of structural network as compared to all existing examples with pyrochlore [12,14], hyperkagome [9], and hyper hyperkagome structure [10,13].…”