S. Suetsugu

The recently discovered superconductor UTe₂ is a promising candidate for spin-triplet superconductors, but the symmetry of the superconducting order parameter remains highly controversial. Here, we determine the superconducting gap structure by the thermal conductivity of ultraclean UTe₂ single crystals. We find that the <i>a</i>-axis thermal conductivity divided by temperature κ/<i>T</i> in zero-temperature limit is vanishingly small for both magnetic field <b><i>H</i></b>

The field-induced quantum-disordered state of layered honeycomb magnet α-RuCl₃ is a prime candidate for Kitaev spin liquids hosting Majorana fermions and non-Abelian anyons. Recent observations of anomalous planar thermal Hall effect demonstrate a topological edge mode, but whether it originates from Majorana fermions or bosonic magnons remains controversial. Here, we distinguish these origins from combined low-temperature measurements of high-resolution specific heat and thermal Hall

The two-dimensional spin-1/2 kagome Heisenberg antiferromagnet is believed to host quantum spin liquid (QSL) states with no magnetic order, but its ground state remains largely elusive. An important outstanding question concerns the presence or absence of the 1/9 magnetization plateau, where exotic quantum states, including topological ones, are expected to emerge. Here we report the magnetization of a recently discovered kagome QSL candidate YCu_{3}(OH)_{6.5}Br_{2.5} up to 57 T. Above 50 T, a c

Novel topological phenomena are anticipated for three-dimensional (3D) Dirac electrons. The magnetotransport properties of cubic ${\mathrm{Sr}}_{3}\mathrm{PbO}$ antiperovskite, theoretically proposed to be a 3D massive Dirac electron system, are studied. The measurements of Shubnikov--de Haas oscillations and Hall resistivity indicate the presence of a low density ($\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{18}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$) of holes

The Kitaev quantum spin liquid (QSL) on the two-dimensional honeycomb lattice epitomizes an entangled topological state, where the spins fractionalize into Majorana fermions. This state has aroused tremendous interest because it harbors non-Abelian anyon excitations. The half-integer quantized thermal Hall (HIQTH) conductance observed in $\alpha$-RuCl$_3$ is a key signature of these excitations. However, the fate of this topologically nontrivial state at intense fields remains largely elusive. H

Interband mixing in Dirac semimetals has been known theoretically to give rise to a giant orbital diamagnetism when the Fermi level is close to the Dirac point. Here, the authors report a ${}^{207}$Pb NMR study on the three-dimensional Dirac antiperovskite system Sr${}_{3}$PbO. The analysis of the Knight shift, the magnetic susceptibility, and the spin-lattice relaxation rate for samples with different Fermi levels shows that the enhanced diamagnetism in the bulk magnetic susceptibility of Sr${}

In contrast to electron (fermion) systems, topological phases of charge neutral bosons have been poorly understood despite recent extensive research on insulating magnets. The most important unresolved issue is how the inevitable inter-bosonic interactions influence the topological properties. It has been proposed that the quantum magnet SrCu$_2$(BO$_3$)$_2$ with an exact ground state serves as an ideal platform for this investigation, as the system is expected to be a magnetic analogue of a Che

Novel topological phenomena are anticipated for three-dimensional (3D) Dirac electrons. The magnetotransport properties of cubic ${\rm Sr_{3}PbO}$ antiperovskite, theoretically proposed to be a 3D massive Dirac electron system, are studied. The measurements of Shubnikov-de Haas oscillations and Hall resistivity indicate the presence of a low density ($\sim 1 \times 10^{18}$ ${\rm cm^{-3}}$) of holes with an extremely small cyclotron mass of 0.01-0.06$m_{e}$. The magnetoresistance $Δρ_{xx}(B)$ is

The two-dimensional (2D) spin-1/2 kagome Heisenberg antiferromagnet is believed to host quantum spin liquid (QSL) states with no magnetic order, but its ground state remains largely elusive. An important outstanding question concerns the presence or absence of the 1/9 magnetization plateau, where exotic quantum states, including topological ones, are expected to emerge. Here we report the magnetization of a recently discovered kagome QSL candidate YCu$_3$(OH)$_{6.5}$Br$_{2.5}$ up to 57 T. Above

We study an anomalous Hall effect in the massive Dirac electron system with broken time reversal symmetry. Using the model Hamiltonian with the spin-orbit interaction and a split term which breaks time reversal symmetry, we calculate the energy band, the Berry curvature and the intrinsic Hall conductivity in an analytical way. We show that the nonzero Berry curvature appears and thus an intrinsic Hall conductivity occurs. This anomalous Hall effect can be observed in such systems as a ferromagne

In contrast to electron (fermion) systems, topological phases of charge neutral bosons have been poorly understood despite recent extensive research on insulating magnets. The most important unresolved issue is how the inevitable interbosonic interactions influence the topological properties. It has been proposed that the quantum magnet $\mathrm{Sr}{\mathrm{Cu}}_{2}{({\mathrm{BO}}_{3})}_{2}$ with an exact ground state serves as an ideal platform for this investigation, as the system is expected