Pure nematic quantum critical point accompanied by a superconducting dome.

SignificanceThe notion of the quantum critical point (QCP) is at the core of modern condensed matter physics. Near a QCP of the symmetry-breaking order, associated quantum-mechanical fluctuations are intensified, which can lead to unconventional superconductivity. Indeed, dome-shaped superconducting phases are often observed near the magnetic QCPs, which supports the spin fluctuation-driven superconductivity. However, the fundamental question remains as to whether a nonmagnetic QCP of electronic nematic order characterized by spontaneous rotational symmetry breaking can promote superconductivity in real materials. Here, we provide an experimental demonstration that a pure nematic QCP exists near the center of a superconducting dome in nonmagnetic FeSe[Formula: see text] Tex. This result evidences that nematic fluctuations enhanced around the nematic QCP can boost superconductivity.

Novel electronic nematicity in heavily hole-doped iron pnictide superconductors.

Electronic nematicity, a correlated state that spontaneously breaks rotational symmetry, is observed in several layered quantum materials. In contrast to their liquid-crystal counterparts, the nematic director cannot usually point in an arbitrary direction (XY nematics), but is locked by the crystal to discrete directions (Ising nematics), resulting in strongly anisotropic fluctuations above the transition. Here, we report on the observation of nearly isotropic XY-nematic fluctuations, via elastoresistance measurements, in hole-doped Ba1-x Rb x Fe2As2 iron-based superconductors. While for [Formula: see text], the nematic director points along the in-plane diagonals of the tetragonal lattice, for [Formula: see text], it points along the horizontal and vertical axes. Remarkably, for intermediate doping, the susceptibilities of these two symmetry-irreducible nematic channels display comparable Curie-Weiss behavior, thus revealing a nearly XY-nematic state. This opens a route to assess this elusive electronic quantum liquid-crystalline state.

Adipose tissue-derived stem cells prevent fibrosis in murine steatohepatitis by suppressing IL-17-mediated inflammation.

BACKGROUND AND AIM: The pathological features of non-alcoholic steatohepatitis (NASH) have not been determined, so fundamental treatment has not been established. Adipose-tissue-derived stromal/stem cells (ADSCs) are beneficial for repair/regenerative therapy of impaired organs because of their immuno-modulatory capability. In this study, we assessed how liver damage progresses during the early development phase of the murine NASH model and investigated whether ADSCs are preventatively efficacious against the fibrosis progression of NASH. METHODS: C57BL/6J mice were fed with atherogenic high fat or high-fat diet 60 developing into NASH or simple steatosis. Their hepatic inflammatory cells (HICs) were analyzed by cDNA microarray. NASH mice were treated with ADSCs injected into spleen when hepatic inflammation was initially observed, and liver samples were analyzed. The effect of ADSCs on the mice hepatic stellate cell (HSC) line stimulated by recombinant IL-17 and HICs from NASH mice was analyzed. RESULTS: The gene expression features of HICs implicated as humoral cytokine mediators of lymphoid cells during NASH development, compared with a simple steatosis model. One of the featured cytokines was IL-17. The development of hepatic fibrosis was alleviated when NASH mice were treated with ADSCs as well as treated with anti-IL-17 antibody, and the frequency of IL-17-secreting HICs decreased. NASH-HICs enhanced proliferation of HSCs, in which proliferation was sensitive to IL-17 stimulation. The stimulatory effect of NASH-HICs on the activation of HSCs was attenuated by co-culture with ADSCs. CONCLUSION: ADSCs treatment prevented progression of NASH fibrosis by suppressing IL-17-mediated inflammation, which was associated with HSCs activation.

Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.

In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.