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A many-body quantum system on the verge of instability between two competing ground states may exhibit quantumcritical phenomena 1,2 , as has been intensively studied for magnetic systems. The Mott metal-insulator transition 3 , a phenomenon that is central to many investigations of strongly correlated electrons, is also supposed to be quantum critical, although this has so far not been demonstrated experimentally. Here, we report experimental evidence for the quantum-critical nature of the Mott instability, obtained by investigating the electron transport of three organic systems with di erent ground states under continuously controlled pressure. The resistivity obeys the material-independent quantum-critical scaling relation bifurcating into a Fermi liquid or Mott insulator, irrespective of the ground states. Electrons on the verge of becoming delocalized behave like a strange quantum-critical fluid before becoming a Fermi liquid.Mutually interacting electrons with sufficiently strong Coulomb repulsion U fall into the Mott insulating state when the carrier density corresponds to an electron per site (a half-filled band) 3 . As the bandwidth W is increased by pressure or chemical substitution, the electrons gain kinetic energy and become itinerant at a critical value of W/U . The Mott transition, a marked phase transition between a metal and an insulator, is a collective manifestation of imbalance in the particle-wave duality of electrons. As one of the main issues in the quantum physics of condensed matter, the quantumcritical nature of the Mott transition awaits clarification. In contrast to intensive theoretical studies 4-6 , however, this issue has not yet been addressed experimentally because most Mott transitions in real systems have critical points at finite temperatures 7-11 ; thus, they are not genuine quantum phase transitions.In general, quantum criticality is observed at the temperature T sufficiently lower than the competing energy scales underlying the phase transition 1,2 , which are the bandwidth W and on-site Coulomb energy U in the case of the Mott transition. Thus, even if the system's critical point, T c , is finite, unlike the genuine quantum phase transition, in the case that T c is orders of magnitude lower than W and U , there is a vast temperature region of T c < T U , W , where the system can experience quantum criticality (Fig. 1a). Indeed, using dynamical mean field theory (DMFT), which can properly describe the Mott transition 12 , the authors of refs 4,13 have suggested the scaling of transport for quantum criticality in an intermediate temperature range well above T c .To explore the possible Mott quantum criticality from the experimental side, we performed pressure studies of the electron transport for three different quasi-two-dimensional organic Mott insulators with anisotropic triangular lattices, κ-(ET) 2 Cu 2 (CN) 3 , κ-(ET) 2 Cu[N(CN) 2 ]Cl and EtMe 3 Sb[Pd(dmit) 2 ] 2 (hereafter abbreviated to κ-Cu 2 (CN) 3 , κ-Cl and EtMe 3 Sb-dmit, respectively), where

The magnetoelectric effect in bulk matter is of growing interest both fundamentally and technologically. Since the beginning of the century, the magnetoelectric effect has been studied intensively in multiferroic materials. However, magnetoelectric phenomena in materials without any (anti-)ferroic order remain almost unexplored. Here we show the observation of a new class of bulk magnetoelectric effect, by revisiting elemental trigonal tellurium. We demonstrate that elemental tellurium, which is a nonmagnetic semiconductor, exhibits current-induced magnetization. This effect is attributed to spin splitting of the bulk band owing to the lack of inversion symmetry in trigonal tellurium. This finding highlights magnetoelectricity in bulk matter driven by moving electrons without any (anti-)ferroic order. Notably, current-induced magnetization generates a magnetic field that is not circular around but is parallel to the applied current; thus, this phenomenon opens a new area of magnetic field generation beyond Ampere’s law that may lead to industrial applications.

The Mott metal-insulator transition—a manifestation of Coulomb interactions among electrons—is known as a discontinuous transition. Recent theoretical studies, however, suggest that the transition is continuous if the Mott insulator carries a spin liquid with a spinon Fermi surface. Here, we demonstrate the case of a quasi-continuous Mott transition from a Fermi liquid to a spin liquid in an organic triangular-lattice system κ-(ET)2Cu2(CN)3. Transport experiments performed under fine pressure tuning have found that as the Mott transition is approached, the Fermi liquid coherence temperature continuously falls to the scale of kelvins, with a divergent quasi-particle decay rate on the metal side, and the charge gap continuously closes on the insulator side. A Clausius-Clapeyron analysis provides thermodynamic evidence for the extremely weak first-order nature of the transition. These results provide additional support for the existence of a spinon Fermi surface, which becomes an electron Fermi surface when charges are delocalized.

Background. Mucus‐hypersecreting tumor of the pancreas appears as dilated ducts and cystic spaces filled with mucus. To determine where such tumors arise and how they extend, computer‐aided three‐dimensional reconstruction was done of the ductal system. This also was used to visualize the spatial relationships among epithelial hyperplasia, dysplasia, and carcinoma in situ (CIS). Methods. Surgically removed pancreases were studied from 12 patients with mucus‐hypersecreting tumors. The specimens were fixed in buffered formaldehyde solution lo%, embedded in paraffin and semiserially sectioned at 3 pm at an interval of 60 pm. The ductal contours were diffentiated among ducts lined by ordinary epithelia, hyperplastic epithelia, dysplastic cells, or CIS and were inputted into a computer system that integrated a three‐dimensional image of ducts in the display. Results and Conclusions. (1) The tumors arose in the main pancreatic duct or its subbranches, and the cysts corresponded to segments expanded by the superficial growth of tumor cells; (2) areas of CIS arose in zones of preceding dysplasia, suggesting a dysplasia‐carcinoma sequence; and (3) dysplastic or cancerous cells often extended intraductally over the dilated segments of ducts.

Quantum spin liquids, which are spin versions of quantum matter, have been sought after in systems with geometrical frustration. We show that disorder drives a classical magnet into a quantum spin liquid through conducting NMR experiments on an organic Mott insulator, κ-(ET)_{2}Cu[N(CN)_{2}]Cl. Antiferromagnetic ordering in the pristine crystal, when irradiated by x rays, disappears. Spin freezing, spin gap, and critical slowing down are not observed, but gapless spin excitations emerge, suggesting a novel role of disorder that brings forth a quantum spin liquid from a classical ordered state.

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By means of a hybrid density-functional method, we investigate the tensile-strain effect of inducing the indirect-to-direct band-gap transition and reducing the band-gap energy of Ge. We consider [001], [111], and [110] uniaxial tensility and (001), (111), and (110) biaxial tensility. Under the condition of no normal stress, we determine both normal compression and internal strain, namely, relative displacement of two atoms in the primitive unit cell, by minimizing the total energy. We identify those strain types which can induce the band-gap transition, and evaluate the critical strain coefficient where the gap transition occurs. Either normal compression or internal strain operates unfavorably to induce the gap transition, which raises the critical strain coefficient or even blocks the transition. We also examine how each type of tensile strain decreases the band-gap energy, depending on its orientation. Our analysis clearly shows that synergistic operation of strain orientation and band anisotropy has a great influence on the gap transition and the gap energy.