Seminar Fizičkog odsjeka / Seminar of the Physics Department

Quantum spin liquids are novel magnetic states of matter characterized by the absence of phase transition down to T=0 K, macroscopic entanglement and emergent fractionalized excitations. The quest for materials realizing such states recently yielded a new family of interesting kagome compounds resulting from the substitution of Zn2+ by Y3+ in the archetypal herbertsmithite ZnCu3(OH)6Cl2 . While charge doping, the initial motivation for the substitution, is not successful, the new materials YCu3(OH)6OxCl3−x (x= 0, 1/3), sometimes coined Y-kapellasite, do not show measurable dilution of the magnetic lattice and provide us with new variations of the kagome structure. The x=0 compound features a perfect kagome geometry and a strong Dzyaloshinskii-Moriya anisotropy which drives a q=0 long range order below 15 K [1]. Here, we present a detailed study using NMR, μSR and neutron scattering techniques of the x=1/3 counterpart which materializes an original anisotropic kagome lattice with 3 different nearest neighbor interactions. NMR and neutron diffraction studies demonstrate the occurrence of a definite structural transition at 33 K and a weaker one at 13 K. These subtle transitions which preserve the global symmetry mainly involve changes in the hydrogen positions. Further, our results provide clear evidence for a magnetic transition at ∼ 2.1 K from complementary experimental methods in contrast to the dynamical ground state reported for powder samples [2] but in line with the theoretical prediction of a (1/3,1/3) long range order [3].

[1] A Zorko et al , Physical Review B, 99 (21), 214441 (2019)
[2] Quentin. et al , Phys. Rev. Materials, 3 (7), 074401 (2019)
[3] Hering et al , npj Comput Mater 8, 10 (2022).