Experimental realization of Lieb-Mattis plateau in a quantum spin chain.

Topological properties in material science have recently received tremendous attention, as exemplified by topological insulators. As for quantum spin systems, the Haldane chain with integer spins is the best known example1. The realization of a topological quantum phase in the Haldane chain is an innovative research development related to the 2016 Nobel Prize in Physics. For mixed spin chains composed of two different spins, the appearance of a topologically quantized magnetization plateau is predicted by the Lieb-Mattis theorem2 in combination with the Oshikawa-Yamanaka-Affleck criterion3. However, the actual magnetization plateau in the mixed spin chain has not yet been observed. Here, we present a model compound forming a mixed spin-(1/2, 5/2) chain. We observe a clear Lieb-Mattis plateau and well explain it quantitatively. The present results demonstrate a quantum many-body effect based on quantum topology and provide a new stage in the search for topological properties in condensed matter physics.

Randomness-induced quantum spin liquid on honeycomb lattice.

Quantum entanglement in magnetic materials is expected to yield a quantum spin liquid (QSL), in which strong quantum fluctuations prevent magnetic ordering even at zero temperature. This topic has been one of the primary focuses of condensed-matter science since Anderson first proposed the resonating valence bond state in a certain spin-1/2 frustrated magnet in 1973. Since then, several candidate materials featuring frustration, such as triangular and kagome lattices, have been reported to exhibit liquid-like behavior. However, the mechanisms that stabilize the liquid-like states have remained elusive. Here, we present a QSL state in a spin-1/2 honeycomb lattice with randomness in the exchange interaction. That is, we successfully introduce randomness into the organic radial-based complex and realize a random-singlet (RS) state (or valence bond glass). All magnetic and thermodynamic experimental results indicate the liquid-like behaviors, which are consistent with those expected in the RS state. Our results suggest that the randomness or inhomogeneity in the actual systems stabilize the RS state and yield liquid-like behavior.

[A case report of the combination therapy with S-1 plus CDDP intraperitoneal chemotherapy for CY positive cancer patient].

A male patient in his 50s underwent distal gastrectomy for gastric cancer. In operation, there was no peritoneal dissemination. But peritoneal lavage cytology revealed positive peritoneal dissemination. Thus, we set an intraperitoneal infuser port to this patient. On specimen, a type-3 tumor was located in the gastric lesser of antrum to angle. Microscopic examination of specimens revealed a signet ring cell carcinoma and poorly differentiated adenocarcinoma under serosa, and positive of lymph node metastasis. The diagnosis was pT4N2M1P0CY1H0, Stage IV( Japanese classification of gastric carcinoma The 14 Edition). CDDP was administered through the infuser port (on day 7, a first dose of 60 mg/m2 and 30 mg/m2 for second) combined with oral administration of S-1 (100 mg/body) for two weeks, with one week of drug withdrawal. This chemotherapy was repeated for 11 courses. After that, peritoneal lavage cytology became negative. S-1 oral administration was continued for four years, and this patient has been well for five years and six months after the surgery. Therefore, it is suggested that intraperitoneal chemotherapy with cisplatin is an effective treatment for microscopical peritoneal dissemination.