arXiv subjects

Hiroyuki Yoshida

Publications and source records attributed to Hiroyuki Yoshida.

21 records · Page 2Linked to original sources

arXiv2009

Vesignieite BaCu3V2O8(OH)2 as a Candidate Spin-1/2 Kagome Antiferromagnet

A polycrystalline sample of vesignieite BaCu3V2O8(OH)2 comprising a nearly ideal kagome lattice composed of Cu2+ ions carrying spin 1/2 has been synthesized and studied by magnetization and heat capacity measurements. Magnetic susceptibility shows a neither long range order, a spin glass transition nor a spin gap down to 2 K, in spite of a moderately strong antiferromagnetic interaction of J/kB = 53 K between nearest-neighbor spins. A broad peak observed at a temperature corresponding to 0.4J in intrinsic magnetic susceptibility indicates a marked development of the short-range order. The ground state of vesignieite is probably a gapless spin liquid or is accompanied by a very small gap less than J/30.

cond-mat.str-el↗

arXiv2008

Unique Phase Transition on Spin-2 Triangular Lattice of Ag2MnO2

Ag2MnO2 is studied as a possible candidate compound for an antiferromagnetic XY spin model on a triangular lattice. In spite of the large Curie-Weiss temperature of -430 K found in magnetic susceptibi-lity, Mn3+ spins with S = 2 do not undergo a conventional long-range order down to 2 K probably owing to the geometrical frustration and two dimensionality in the system. Instead, a unique phase transition is found at 80 K, where specific heat exhibits a clear sign of a second-order phase transition, while magnetic susceptibility changes smoothly without a distinct anomaly. We think that this transition is related to the chirality degree of freedom associated with a short-range order, which has been expected for the classical XY spin model on a triangular lattice. On further cooling, spin-glass-like behavior is observed below 22 K, possibly corresponding to a quasi-long-range order.

cond-mat.str-el↗

arXiv1994

On Calculations of Zeros of Various L-functions

As we have shown several years ago [Y2], zeros of $L(s, Δ)$ and $L^(2)(s, Δ)$ can be calculated quite efficiently by a certain experimental method. Here $Δ$ denotes the cusp form of weight 12 with respect to SL$(2, Z)$ and $L(s, Δ)$ (resp. $L^(2)(s, Δ)$) denotes the standard (resp. symmetric square) $L$-function attached to $Δ$. The purpose of this paper is to show that this method can be applied to a wide class of $L$-functions so that we can obtain precise numerical values of their zeros.

math.NT↗