Quantum spin liquid ground state in a rare-earth triangular antiferromagnet SmTa$_7$O$_{19}$

Dhanpal Bairwa; Abhisek Bandyopadhyay; Devashibhai Adroja; G. B. G. Stenning; Hubertus Luetkens; Thomas James Hicken; Jonas A. Krieger; G. Cibin; M. Rotter; S. Rayaprol; P. D. Babu; Suja Elizabeth

arXiv · 2503.04631

Quantum spin liquid ground state in a rare-earth triangular antiferromagnet SmTa$_7$O$_{19}$

Dhanpal Bairwa·Abhisek Bandyopadhyay·Devashibhai Adroja·G. B. G. Stenning·Hubertus Luetkens·Thomas James Hicken·Jonas A. Krieger·G. Cibin·M. Rotter·S. Rayaprol·P. D. Babu·Suja Elizabeth

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Abstract

The rare-earth-based geometrically frustrated triangular magnets have attracted considerable attention due to the intricate interplay between strong spin-orbit coupling and the crystal electric field (CEF), which often leads to effective spin-1/2 degrees of freedom and therefore promotes strong quantum fluctuations at low temperatures, thus offering an excellent route to stabilize a quantum spin liquid (QSL) ground state. We have investigated the ground state magnetic properties of a polycrystalline sample of $\text{SmTa}_7\text{O}_{19}$ which we propose to have a gapless QSL ground state by employing powder X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), DC and AC-magnetic susceptibility, $M$ vs. $H$ isotherm, specific heat, and muon spin rotation/relaxation measurements ($\mu$SR) down to 30 mK. The combined structural and electronic studies reveal the formation of an edge-sharing equilateral triangular lattice of Sm$^{3+}$ ions in $ab$ plane. The DC, AC magnetic susceptibility, and heat capacity measurements reveal that $\text{SmTa}_7\text{O}_{19}$ does not exhibit any long-range magnetic ordering transition down to 50 mK. The zero-field (ZF)-$\mu$SR study strongly refutes the long-range magnetically ordered ground state and/or any partial spin-freezing down to at least 30 mK. The ZF-muon-spin relaxation rate is weakly temperature dependent between 50 and 20 K, rapidly increases below $\sim$20 K and saturates at low temperatures between 2 K and 30 mK, which has been attributed to a characteristic signature of QSL systems. Further, our longitudinal-field (LF)-$\mu$SR measurements at 0.1 K reveal a dynamic nature of the magnetic ground state. In addition, our high-field specific heat data suggest a gapless nature of spin excitations in this compound.

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Dhanpal Bairwa, Abhisek Bandyopadhyay, Devashibhai Adroja, G. B. G. Stenning, Hubertus Luetkens, Thomas James Hicken, Jonas A. Krieger, G. Cibin, M. Rotter, S. Rayaprol, P. D. Babu, Suja Elizabeth. 2025-03-06. Quantum spin liquid ground state in a rare-earth triangular antiferromagnet SmTa$_7$O$_{19}$. https://arxiv.org/abs/2503.04631

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