Antiferromagnetically coupled S=1/2 spins on an isotropic triangular lattice is the paradigm of frustrated quantum magnetism, but structurally ideal realizations are rare. Here we investigate NaYbO2, which hosts an ideal triangular lattice of Jeff=1/2 moments with no inherent site disorder. No signatures of conventional magnetic order appear down to 50 mK, strongly suggesting a quantum spin liquid ground state. We observe a two-peak specific heat and a nearly quadratic temperature dependence in accord with expectations for a two-dimensional Dirac spin liquid. Application of a magnetic field strongly perturbs the quantum disordered ground state and induces a clear transition into a collinear ordered state consistent with a long-predicted "up-up-down" structure for a triangular lattice XXZ Hamiltonian driven by quantum fluctuations. The observation of spin liquid signatures in zero field and quantum-induced ordering in intermediate fields in the same compound demonstrate an intrinsically quantum disordered ground state. We conclude that NaYbO2 is a model, versatile platform for exploring spin liquid physics with full tunability of field and temperature.Exotic ground states of quantum antiferromagnets are encouraged by the combination of low dimensionality, geometric frustration, and inherent anisotropies. Planar triangular lattices have long been sought as platforms for stabilizing them 1-7 ; however, ideal manifestations that do not break crystallographic or exchange symmetries upon approaching the quantum regime are rare. The organic compounds κ-(BEDT-TTF)2Cu2(CN)3 8 and EtMe3Sb[Pd(dmit)2]2 9 are two promising examples of triangular lattices with S=1/2 moments and a dynamically disordered spin ground state. However, S=1/2 inorganic analogs such as Ba3CoSb2O9 10 , Ba8CoNb6O24 11 , and NaTiO2 12-14 either order magnetically or undergo a lattice deformation and dimerization upon cooling. A key roadblock in inorganic systems is the identification of a material with a high crystallographic symmetry, rigid structure, and minimal defect mechanisms that also contains magnetic ions possessing strong quantum fluctuations. Ideally, the magnetic ions should be located at high symmetry positions that preclude antisymmetric Dzyaloshinskii-Moriya exchange from lifting geometric frustration at low temperatures.As an alternative to S=1/2 based compounds, rare earth ions with ground state doublets may also engender enhanced quantum fluctuations when decorating a triangular lattice. Specifically, recent studies have shown that the spin-orbit entangled Jeff=1/2 moments of Yb 3+ ions on this lattice may exhibit a variety of nearly degenerate magnetic states 15-22 . Given the appropriate anisotropies and when driven close

The evolution of the electronic properties of electron-doped (Sr1−xLax)2IrO4 is experimentally explored as the doping limit of La is approached. As electrons are introduced, the electronic ground state transitions from a spin-orbit Mott phase into an electronically phase separated state, where long-range magnetic order vanishes beyond x = 0.02 and charge transport remains percolative up to the limit of La substitution (x ≈ 0.06). In particular, the electronic ground state remains inhomogeneous even beyond the collapse of the parent state's long-range antiferromagnetic order, while persistent short-range magnetism survives up to the highest La-substitution levels. Furthermore, as electrons are doped into Sr2IrO4, we observe the appearance of a low temperature magnetic glass-like state intermediate to the complete suppression of antiferromagnetic order. Universalities and differences in the electron-doped phase diagrams of single layer and bilayer Ruddlesden-Popper strontium iridates are discussed.

Hybrid main group halide perovskites hold great technological promise in optoelectronic applications and present rich and complex evolution of structure and dynamics. Here we present low-temperature dielectric measurements and calorimetry of APbI3 [A = CH3NH3 +, HC­(NH2)2 +] that suggest glassy behavior on cooling. In both compounds, the dielectric loss displays frequency-dependent peaks below 100 K characteristic of a glassy slowing of relaxation dynamics, with HC­(NH2)2PbI3 exhibiting greater glass fragility. Consistent with quenched disorder, the low-temperature heat capacity of both perovskites deviates substantially from the ∼T 3 acoustic phonon contribution predicted by the Debye model. We suggest that static disorder of the A-site molecular cation, potentially coupled to local distortions of the Pb–I sublattice, is responsible for these phenomena. The distinct low-temperature dynamics observed in these two perovskites suggest qualitative differences in the interaction between the molecular cation and the surrounding inorganic framework, with potential implications for defect screening and device performance at ambient temperatures.