Gapless dynamic magnetic ground state in the charge-gapped trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$

Abstract

We present an experimental investigation of the magnetic ground state in Ba${}_4$NbIr${}_3$O${}_{12}$, a fractional valent trimer iridate. X-ray absorption and photoemission spectroscopy show that the Ir valence lies between 3+ and 4+ while Nb is pentavalent. Combined dc/ac magnetization, specific heat, and muon spin rotation/relaxation ($\mu$SR) measurements reveal no magnetic phase transition down to 0.05~K. Despite a significant Weiss temperature (${\Theta }_{\mathrm{W}}\sim -15$ to $-25$~K) indicating antiferromagnetic correlations, a quantum spin-liquid (QSL) phase emerges and persists down to 0.1~K. This state likely arises from geometric frustration in the edge-sharing equilateral triangle Ir network. Our $\mu$SR analysis reveals a two-component depolarization, arising from the coexistence of rapidly (90\%) and slowly (10\%) fluctuating Ir moments. Powder x-ray diffraction and Ir-L${}_3$edge x-ray absorption fine structure spectroscopy identify ~8-10\% Nb/Ir site-exchange, reducing frustration within part of the Ir network, and likely leading to the faster muon spin relaxation, while the structurally ordered Ir ions remain highly geometrically frustrated, giving rise to the rapidly spin-fluctuating QSL ground state. At low temperatures, the magnetic specific heat varies as $\gamma T+\alpha T^2$, indicating gapless spinon excitations, and possible Dirac QSL features with linear spinon dispersion, respectively.

27 pages, 15 figures

References in corpus (43)

• Anyons in an exactly solved model and beyond
• Quantum Spin Liquids
• Mantid - Data Analysis and Visualization Package for Neutron Scattering and $\mu SR$ Experiments
• Fermi-liquid instabilities at magnetic quantum phase transitions
• Spin Dynamics of the Spin-1/2 Kagome Lattice Antiferromagnet ZnCu_3(OH)_6Cl_2
• Spin-Liquid State in the S = 1/2 Hyperkagome Antiferromagnet Na4Ir3O8
• Physics of the Kitaev model: fractionalization, dynamical correlations, and material connections
• Evidence for a spinon Fermi surface in a triangular lattice quantum spin liquid candidate
• Gapless quantum spin liquid ground state in the two-dimensional spin-1/2 triangular antiferromagnet YbMgGaO${}_4$
• $\mu$SR evidence for the U(1) quantum spin liquid ground state in the triangular antiferromagnet YbMgGaO${}_4$
• Valence Bonds in Random Quantum Magnets: Theory and Application to YbMgGaO4
• High pressure sequence of Ba_3NiSb_2O_9 structural phases: new $S=1$ quantum spin-liquids based on Ni^{2+}
• Possible valence-bond condensation in the frustrated cluster magnet LiZn2Mo3O8
• Valence bond glass on an fcc lattice in the double perovskite Ba2YMoO6
• Scaling and data collapse from local moments in frustrated disordered quantum spin systems
• Gapless spin liquid ground state in the S=1/2 vanadium oxyfluoride kagome antiferromagnet [NH4]2[C7H14N][V7O6F18]
• Gapless spin liquids on the three dimensional hyper-kagome lattice of Na${}_4$Ir${}_3$O${}_8$
• Spin-liquid-like state in a spin-1/2 square-lattice antiferromagnet perovskite induced by $d^{10}$-$d^0$ cation mixing
• Hexagonal Perovskites as Quantum Materials
• X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6
• Na4Ir3O8 as a 3D spin liquid with fermionic spinons
• Spin liquid behaviour in Jeff=1/2 triangular lattice Ba3IrTi2O9
• Bond disordered spin liquid and the honeycomb iridate H${}_3$LiIr${}_2$O${}_6$ $-$ abundant low energy density of states from random Majorana hopping
• Spin-orbital liquid state assisted by singlet-triplet excitation in $J=0$ ground state of Ba${}_3$ZnIr${}_2$O${}_9$
• Two-dimensional spin liquid behaviour in the triangular-honeycomb antiferromagnet TbInO${}_3$
• Thermodynamic Evidence of Proximity to a Kitaev Spin-Liquid in Ag${}_3$LiIr${}_2$O${}_6$
• Exotic low-energy excitations emergent in the random Kitaev magnet Cu${}_2$IrO${}_3$
• Singlet Ground State of the Quantum Antiferromagnet Ba3CuSb2O9
• Persistent low-temperature spin dynamics in the mixed-valence iridate Ba${}_3$InIr${}_2$O${}_9$
• Origin of magnetic moments and presence of a resonating valence bond state in Ba${}_2$YIrO${}_6$
• Local Magnetism and Spin Dynamics of the Frustrated Honeycomb Rhodate Li2RhO3
• Gapless quantum spin liquid in the triangular system Sr${}_3$CuSb${}_2$O${}_9$
• Signatures of a spin-1/2 cooperative paramagnet in the diluted triangular lattice of Y${}_2$CuTiO${}_6$
• Ba${}_3$M${}_x$Ti${}_{3-x}$O${}_9$(M = Ir, Rh): A family of 5\textit{\textcolor{black}{d}}/4\textit{\textcolor{black}{d}}-based, diluted quantum spin liquids
• A Geometrically Frustrated Trimer-Based Mott Insulator
• How to measure a spinon Fermi surface
• The trimer-based spin liquid candidate Ba4NbIr3O12
• Absence of magnetic long range order in Ba${}_3$ZnRu${}_2$O${}_9$: A spin-liquid candidate in the $S=3/2$ dimer lattice
• Unconventional magnetism in the spin-orbit driven Mott insulators Ba3MIr2O9 (M=Sc,Y)
• Charge transfer energy in iridates: a hard x-ray photoelectron spectroscopy study
• Spin liquid behavior of a three-dimensional magnetic system Ba${}_3$NiIr${}_2$O${}_9$ with $S$ = 1
• Quantum critical spin-liquid-like behavior in S = 1/2 quasikagome lattice CeRh1-xPdxSn investigated using muon spin relaxation and neutron scattering
• Correlated electron metal properties of the honeycomb ruthenate Na${}_2$RuO${}_3$

Cited by in corpus (2)

• Scaling and data collapse of two-dimensional random singlet state in magnetic field
• Cluster Spin Glass State in Ba${}_3$Sb${}_{1+x}$Co${}_{2-x}$O${}_{9-\delta }$: Cation Disorder and Mixed-Valence Co Dimers