Satoru Nakatsuji

As liquids crystallize into solids on cooling, spins in magnets generally form periodic order. However, three decades ago, it was theoretically proposed that spins on a triangular lattice form a liquidlike disordered state at low temperatures. Whether or not a spin liquid is stabilized by geometrical frustration has remained an active point of inquiry ever since. Our thermodynamic and neutron measurements on NiGa2S4, a rare example of a two-dimensional triangular lattice antiferromagnet, demonst

We have revealed the phase diagram of Ca2-xSrxRuO4: the quasi-two-dimensional Mott transition system that connects the Mott insulator Ca2RuO4 with the spin-triplet superconductor Sr2RuO4. Adjacent to the metal/nonmetal transition at x approximately 0.2, we found an antiferromagnetically correlated metallic region where non-Fermi-liquid behavior in resistivity is observed. Besides this, the critical enhancement of susceptibility toward the region boundary at x(c) approximately 0.5 suggests the cr

Strongly frustrated magnetism of the metallic pyrochlore oxide Pr2Ir2O7 has been revealed by single crystal study. While Pr 4f moments have an antiferromagnetic RKKY interaction energy scale of /T*/ = 20 K mediated by Ir 5d-conduction electrons, no magnetic long-range order is found except for partial spin freezing at 120 mK. Instead, the Kondo effect, including a lnT dependence in the resistivity, emerges and leads to a partial screening of the moments below /T*/. Our results indicate that the

Noncuprate layered perovskite Sr 2 RuO 4 is a highly correlated metal and exhibits superconductivity below T c ≈1.35 K. We have newly synthesized related layered ruthenates Ca 2 RuO 4 in two distinct structural phases with substantially different aspect ratios c / a . Electrical and magnetic measurements show that the two phases are insulating antiferromagnets. We argue that both phases of Ca 2 RuO 4 are Mott insulators. The decrease of the 4 d band width in comparison with that of Sr 2 RuO 4 ,

We present a two-fluid description of the Kondo lattice that is based on an analysis of CeCoIn5 at various levels of dilution with La. We show that thermal and transport measurements provide evidence for the survival of the Kondo impurity component in the lattice as T-->0 K, and that the evolution of the low temperature properties of the Kondo lattice can be viewed as the partial condensation of the lattice of Kondo centers into a heavy fermion fluid. The resulting two-fluid model is shown to be

We studied the structural, magnetic, and transport properties of the quasi-two-dimensional Mott transition system ${\mathrm{Ca}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{RuO}}_{4}.$ In the vicinity of the metal-nonmetal (M-NM) transition at $x\ensuremath{\simeq}0.2,$ we found a structural transition accompanied by a structural symmetry change with the instability point at ${x}_{\mathrm{c}}\ensuremath{\simeq}0.5.$ The critical change across the structural transition in the temperature dependen

Low temperature magnetic, thermal, and transport measurements in ${\mathrm{C}\mathrm{a}}_{2\ensuremath{-}x}{\mathrm{S}\mathrm{r}}_{x}{\mathrm{R}\mathrm{u}\mathrm{O}}_{4}$ clarify the appearance of a cluster glass phase, after the evolution of a nearly ferromagnetic heavy-mass Fermi liquid from the spin-triplet superconductor ${\mathrm{S}\mathrm{r}}_{2}{\mathrm{R}\mathrm{u}\mathrm{O}}_{4}$. As the Mott transition is approached across a 2nd-order structural transition, both the magnetization and s

Frustrated magnetic materials, in which local conditions for energy minimization are incompatible because of the lattice structure, can remain disordered to the lowest temperatures. Such is the case for Ba(3)CuSb(2)O(9), which is magnetically anisotropic at the atomic scale but curiously isotropic on mesoscopic length and time scales. We find that the frustration of Wannier's Ising model on the triangular lattice is imprinted in a nanostructured honeycomb lattice of Cu(2+) ions that resists a co

The La dilution of the Kondo lattice CeCoIn5 is studied. The scaling laws found for the magnetic susceptibility and the specific heat reveal two well-separated energy scales, corresponding to the single-impurity Kondo temperature T(K) and an intersite spin-liquid temperature T(*). The Ce-dilute alloy has the expected Fermi liquid ground state, while the specific heat and resistivity in the dense Kondo regime exhibit non-Fermi-liquid behavior, which scales with T(*). These observations indicate t

Macroscopic responses of magnets are often governed by magnetization and, thus, have been restricted to ferromagnets. However, such responses are strikingly large in the newly developed topological magnets, breaking the conventional scaling with magnetization. Taking the recently discovered antiferromagnetic (AF) Weyl semimetals as a prime example, we highlight the two central ingredients driving the significant macroscopic responses: the Berry curvature enhanced because of nontrivial band topol