Masafumi Udagawa

Exact Result of Ground-State Entropy for Ising Pyrochlore Magnets under a Magnetic Field along (111) Axis

field but there remains a frustrated spin system which causes the ground-state entropy. In this paper, we study the ground-state entropy or the ground-state degeneracy considering this physical picture. We find that the exact number of ground-state degeneracies under a magnetic field can be obtained. It is worth noting that Pauling’s estimation of the ground-state entropy without magnetic field is only approximate. We will compare our exact result with the estimate obtained by extending Pauling’s approximation to the present case. Actually we find that the difference is only 10%, so that we expect Pauling’s estimation for the three-dimensional pyrochlore lattice to also be reasonable.

Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials.

Three-dimensional condensed matter incarnations of Weyl fermions generically have a tilted dispersion-in sharp contrast to their elusive high-energy relatives where a tilt is forbidden by Lorentz invariance, and with the low-energy excitations of two-dimensional graphene sheets where a tilt is forbidden by either crystalline or particle-hole symmetry. Very recently, a number of materials (MoTe_{2}, LaAlGe, and WTe_{2}) have been identified as hosts of so-called type-II Weyl fermions whose dispersion is so strongly tilted that a Fermi surface is formed, whereby the Weyl node becomes a singular point connecting electron and hole pockets. We here predict that these systems have remarkable properties in the presence of magnetic fields. Most saliently, we show that the nature of the chiral anomaly depends crucially on the relative angle between the applied field and the tilt, and that an inversion-asymmetric overtilting creates an imbalance in the number of chiral modes with positive and negative slopes. The field-selective anomaly gives a novel magneto-optical resonance, providing an experimental way to detect concealed Weyl nodes.

Thermal fractionalization of quantum spins in a Kitaev model: Temperature-linear specific heat and coherent transport of Majorana fermions

Finite-temperature (

Vaporization of Kitaev Spin Liquids

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Topology and Interactions in a Frustrated Slab: Tuning from Weyl Semimetals to C > 1 Fractional Chern Insulators

) properties of a Kitaev model defined on a honeycomb lattice are investigated by a quantum Monte Carlo simulation, from the viewpoint of fractionalization of quantum

Hidden Multiple-Spin Interactions as an Origin of Spin Scalar Chiral Order in Frustrated Kondo Lattice Models

S=1/2

Non-Kondo mechanism for resistivity minimum in spin ice conduction systems.

spins into two types of Majorana fermions, itinerant and localized. In this system, the entropy is released successively at two well-separated

Formation of non-unitary state near the upper-critical field of Sr2RuO4

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Magnetic Order and Charge Disproportionation in a Spin-Ice Type Kondo Lattice Model: Large Scale Monte Carlo Study

scales, as a clear indication of the thermal fractionalization. We show that the high-

Partial Disorder in the Periodic Anderson Model on a Triangular Lattice

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