The recent discovery of large magnetoresistance in tungsten ditelluride provides a unique playground to find new phenomena and significant perspective for potential applications. The large magnetoresistance effect originates from a perfect balance of hole and electron carriers, which is sensitive to external pressure. Here we report the suppression of the large magnetoresistance and emergence of superconductivity in pressurized tungsten ditelluride via high-pressure synchrotron X-ray diffraction, electrical resistance, magnetoresistance and alternating current magnetic susceptibility measurements. Upon increasing pressure, the positive large magnetoresistance effect is gradually suppressed and turned off at a critical pressure of 10.5 GPa, where superconductivity accordingly emerges. No structural phase transition is observed under the pressure investigated. In situ high-pressure Hall coefficient measurements at low temperatures demonstrate that elevating pressure decreases the population of hole carriers but increases that of the electron ones. Significantly, at the critical pressure, a sign change of the Hall coefficient is observed.

Here we report the first in-situ high pressure (up to ~ 50 GPa) Hall effect measurements on single crystal black phosphorus. We find a strong correlation between the sign of the Hall coefficient, an indicator of the dominant carrier type, and the superconducting transition temperature (T C). Importantly, we find a change from electron-dominant to hole-dominant carriers in the simple cubic phase of phosphorus at a pressure of ~17.2 GPa, providing an explanation for the puzzling valley it displays in its superconducting T C vs. pressure phase diagram. Our results reveal that hole-carriers play an important role in developing superconductivity in elemental phosphorus, and the valley in T C at 18.8 GPa is associated with a Lifshitz transition.

Purpose To determine if summary estimates of a self-report physical activity questionnaire that does not specifically assess frequency or duration [the Coronary Artery Risk Development in Young Adults (CARDIA) Physical Activity History (PAH)] differs from the summary estimates of one that does (CARDIA Supplemental Questionnaire). Methods Following the Year 25 exam (2010–11), 203 CARDIA black and white men and women (aged 50.3 ± 3.6 years) at the Oakland, CA site participated in this comparison study. The between-questionnaire association and agreement was determined for continuous and categorical estimates based on (1) quartiles and (2) meeting 2008 Physical Activity Guidelines. Differences in participant characteristics by concordance/discordance status were also examined. Finally, receiver operating characteristic (ROC) curves were computed to determine the accuracy of the PAH compared to the supplemental questionnaire. Results Reported physical activity levels were high and varied significantly by race and sex (all p<0.01). Between-questionnaire estimates were significantly correlated (rho= 0.75 to 0.90; all p<0.001) and had high agreement (κ = 0.51 to 0.80) across all race/sex groups. A higher proportion of women than men were classified as concordant by quartile of vigorous intensity (p=0.001), but no other participant characteristics were associated with concordant/discordant quartile ranking. Participants classified as concordant based on PA guidelines had lower body mass index than those classified as discordant (both p<0.05). The AUC was 0.95 suggesting that the PAH has high accuracy for classifying individuals as meeting physical activity guidelines. Conclusions Although it is inconvenient that the PAH is not expressed in more standard units, these findings support the practice of not directly assessing frequency and duration, which are frequent sources of reporting error.

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