박병재 교수

Finding new materials with antiferromagnetic (AFM) Kitaev interaction is an urgent issue for quantum magnetism research. We conclude that Na₃Co₂SbO₆and Na₂Co₂TeO₆are new honeycomb cobalt-based systems with AFM Kitaev interaction by carrying out inelastic neutron scattering experiments and subsequent analysis. The spin-orbit excitons observed at 20-28 meV in both compounds strongly support the idea that Co²⁺ions of both

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120° structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF Co_1/3TaS₂ as the first example of tetrahedral triple-Q magnetic ordering with the associated topological Hall

Abstract Combining magnetism with band topology provides various novel phases that are otherwise impossible. Among several cases, noncollinear metallic antiferromagnets can reveal particularly rich topological physics due to their diverse magnetic ground states. However, there are only a few experimental studies due to the lack of suitable materials, especially with triangular lattice antiferromagnets. Here, we report that metallic triangular antiferromagnet Co 1/3 TaS 2 exhibits a substantial a

Spontaneous Hall conductivity has recently been reported in the triangular lattice antiferromagnet ${\mathrm{Co}}_{1/3}\mathrm{Ta}{\mathrm{S}}_{2}$ under a zero magnetic field. This phenomenon originates from the distinctive noncoplanar triple-Q magnetic ground state, possessing uniform real-space Berry curvature characterized by scalar spin chirality. We investigated the physical properties of ${\mathrm{Co}}_{1/3}\mathrm{Ta}{\mathrm{S}}_{2}$ by judiciously controlling the composition, revealing

Novel effects induced by nonmagnetic impurities in frustrated magnets and quantum spin liquid represent a highly nontrivial and interesting problem. A theoretical proposal of extended modulated spin structures induced by doping of such magnets, distinct from the well-known skyrmions has attracted significant interest. Here, we demonstrate that nonmagnetic impurities can produce such extended spin structures in h-YMnO₃, a triangular antiferromagnet with noncollinear magnetic order. Usi

Kagome metals with van Hove singularities near the Fermi level can host intriguing quantum phenomena such as chiral loop currents, electronic nematicity, and unconventional superconductivity. However, to our best knowledge, unconventional magnetic states driven by van Hove singularities-like spin-density waves-have not been observed experimentally in kagome metals. Here, we report the magnetic and electronic structure of the layered kagome metal CeTi₃Bi₄, where Ti kagome el

Noncollinear magnetic order arises for various reasons in several magnetic systems and exhibits interesting spin dynamics. Despite its ubiquitous presence, little is known of how magnons, otherwise stable quasiparticles, decay in these systems, particularly in metallic magnets. Using inelastic neutron scattering, we examine the magnetic excitation spectra in a metallic noncollinear antiferromagnet CrB_{2}, in which Cr atoms form a triangular lattice and display incommensurate magnetic order. Our

This work establishes Yb-containing oxyhalides as a new family of materials for studying quantum magnetism on a frustrated square lattice. The titular compounds appear to possess long-range magnetic order below \ensuremath{\approx}0.21 K (YbBi${}_{2}$lO${}_{4}$), but analysis of their thermodynamic properties via a ${J}_{1}$-${J}_{2}$ square lattice model suggests large magnetic frustration. This places the materials near the transition to a quantum spin liquid. Thus, the impact of quantum fluct

Using the framework of semiclassical Landau-Lifshitz dynamics (LLD), we conduct a systematic investigation of the temperature-dependent spin dynamics in the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>S</a:mi><a:mo>=</a:mo><a:mn>1</a:mn><a:mo>/</a:mo><a:mn>2</a:mn></a:mrow></a:math> Heisenberg square-lattice antiferromagnet (SAFM). By performing inelastic neutron scattering measurements on <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msub><b:mi>Zn</b:mi>

The S = 1/2 triangular lattice antiferromagnet (TLAF) is a paradigmatic example of frustrated quantum magnetism. An ongoing challenge involves understanding the influence of exchange anisotropy on the collective behavior within such systems. Using inelastic neutron scattering (INS) and advanced calculation techniques, we have studied the low and high-temperature spin dynamics of Ba₂La₂CoTe₂O₁₂ (BLCTO): a Co²⁺-based J_eff = 1/2 TLAF

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120 structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF Co1/3TaS2 as the first example of tetrahedral triple-Q magnetic ordering with the associated topological Hall effect (non-zero σ_{xy}

Multi-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi mathvariant="bold">Q</a:mi></a:math> magnetic structures on two-dimensional (2D) lattices provide a key route to realizing topological physics in 2D magnetism. A major experimental challenge is to unambiguously confirm their formation by excluding the possibility of topologically trivial multidomain single- or double-<d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mi mathvariant="bold">Q</d

Kagome metals with van Hove singularities near the Fermi level can host intriguing quantum phenomena such as chiral loop currents, electronic nematicity, and unconventional superconductivity. However, to our best knowledge, unconventional magnetic states driven by van Hove singularities--like spin-density waves--have not been observed experimentally in kagome metals. Here, we report the magnetic and electronic structure of the layered kagome metal CeTi3Bi4, where Ti kagome electronic structure i

We report on the crystal field level splitting and magnetic ground state of the ${J}_{\mathrm{eff}}=1/2$ square lattice antiferromagnets ${\mathrm{YbBi}}_{2}{\mathrm{ClO}}_{4}$ and ${\mathrm{YbBi}}_{2}{\mathrm{IO}}_{4}$ using powder inelastic neutron scattering (INS) and neutron diffraction measurements. Both compounds exhibit a well-isolated ${\mathrm{\ensuremath{\Gamma}}}_{7}$ doublet ground state under a tetragonal crystal field environment, confirming a robust ${J}_{\mathrm{eff}}=1/2$ pictur

Spontaneous Hall conductivity has recently been reported in the triangular lattice antiferromagnet Co$_{1/3}$TaS$_2$ under a zero magnetic field. This phenomenon originates from the distinctive noncoplanar triple-Q magnetic ground state, possessing uniform real-space Berry curvature characterized by scalar spin chirality. We investigated the physical properties of Co$_{1/3}$TaS$_2$ by judiciously controlling the composition, revealing a drastic change in its bulk properties, even by slight varia