2025-09-30 アルゴンヌ国立研究所（ANL）
Topologically protected quantum spin liquid under extreme pressure in diamond anvil cell. Honeycomb structure shown with frustrated and entangled electron spins. (Image by Argonne National Laboratory.)
＜関連情報＞
- https://www.anl.gov/article/scientists-explore-new-spin-on-quantum-computing
- https://www.nature.com/articles/s42005-025-02174-2
- https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.067201
キタエフスピン液体候補物質Na3Co2SbO 6 の圧力調整 Pressure tuning of Kitaev spin liquid candidate Na3Co2SbO6
E. H. T. Poldi,R. Tartaglia,G. Fabbris,N. Nguyen,H. Park,Z. Liu,M. van Veenendaal,R. Kumar,G. Jose,S. Samanta,W. Bi,Y. Xiao,D. Popov,Y. Wu,J.-W. Kim,H. Zheng,J. Yan,J. F. Mitchell,R. J. Hemley & D. Haskel
Communications Physics Published:29 July 2025
DOI:https://doi.org/10.1038/s42005-025-02174-2
Abstract
The search for Kitaev’s quantum spin liquid in real materials has recently expanded with the prediction that honeycomb lattices of divalent, high-spin cobalt ions could host the dominant bond-dependent exchange interactions required to stabilize the elusive entangled quantum state. The layered honeycomb Na3Co2SbO6 has been singled out as a leading candidate provided that the trigonal crystal field acting on Co 3d orbitals, which enhances non-Kitaev exchange interactions Jeff=1/2 between spin-orbital pseudospins, is reduced. Here we show that applied pressure leads to anisotropic compression of the layered structure, significantly reducing the trigonal distortion of CoO6 octahedra. Ferromagnetic correlations between pseudospins are enhanced in the spin-polarized (3 Tesla) phase up to about 60 GPa. Higher pressures drive a high-spin to low-spin transition destroying the Jeff=1/2 moments required to map the spin Hamiltonian into Kitaev’s model. The spin transition strongly suppresses the low-temperature magnetic susceptibility and appears to stabilize a paramagnetic phase driven by frustration. The possible emergence of frustrated magnetism of localized S=1/2 moments opens the door for exploration of novel magnetic quantum states in compressed honeycomb lattices of divalent cobaltates.
圧縮Sr₂IrO₄における量子常磁性の可能性 Possible Quantum Paramagnetism in Compressed Sr2IrO4
D. Haskel, G. Fabbris, J. H. Kim, L. S. I. Veiga, J. R. L. Mardegan, C. A. Escanhoela, Jr., S. Chikara, V. Struzhkin, T. Senthil et al.
Physical Review Letters Published 11 February, 2020
DOI: https://doi.org/10.1103/PhysRevLett.124.067201
Abstract
The effect of compression on the magnetic ground state of Sr2IrO4 is studied with x-ray resonant techniques in the diamond anvil cell. The weak interlayer exchange coupling between square-planar 2D IrO2 layers is readily modified upon compression, with a crossover between magnetic structures around 7 GPa mimicking the effect of an applied magnetic field at ambient pressure. Higher pressures drive an order-disorder magnetic phase transition with no magnetic order detected above 17–20 GPa. The persistence of strong exchange interactions between eff =1/2 magnetic moments within the insulating IrO2 layers up to at least 35 GPa points to a highly frustrated magnetic state in compressed Sr2IrO4, opening the door for realization of novel quantum paramagnetic phases driven by extended 5 orbitals with entangled spin and orbital degrees of freedom.
