Spectroscopy of bulk and few-layer superconducting NbSe2 with van der Waals tunnel junctions.

Tunnel junctions, an established platform for high resolution spectroscopy of superconductors, require defect-free insulating barriers; however, oxides, the most common barrier, can only grow on a limited selection of materials. We show that van der Waals tunnel barriers, fabricated by exfoliation and transfer of layered semiconductors, sustain stable currents with strong suppression of sub-gap tunneling. This allows us to measure the spectra of bulk (20 nm) and ultrathin (3- and 4-layer) NbSe2 devices at 70 mK. These exhibit two distinct superconducting gaps, the larger of which decreases monotonically with thickness and critical temperature. The spectra are analyzed using a two-band model incorporating depairing. In the bulk, the smaller gap exhibits strong depairing in in-plane magnetic fields, consistent with high out-of-plane Fermi velocity. In the few-layer devices, the large gap exhibits negligible depairing, consistent with out-of-plane spin locking due to Ising spin-orbit coupling. In the 3-layer device, the large gap persists beyond the Pauli limit.

Entanglement swapping between photons that have never coexisted.

The role of the timing and order of quantum measurements is not just a fundamental question of quantum mechanics, but also a puzzling one. Any part of a quantum system that has finished evolving can be measured immediately or saved for later, without affecting the final results, regardless of the continued evolution of the rest of the system. In addition, the nonlocality of quantum mechanics, as manifested by entanglement, does not apply only to particles with spacelike separation, but also to particles with timelike separation. In order to demonstrate these principles, we generated and fully characterized an entangled pair of photons that have never coexisted. Using entanglement swapping between two temporally separated photon pairs, we entangle one photon from the first pair with another photon from the second pair. The first photon was detected even before the other was created. The observed two-photon state demonstrates that entanglement can be shared between timelike separated quantum systems.

Self-fulfilling prophecy and gender: can women be Pygmalion and galatea?

To date, all published confirmations of the Pygmalion hypothesis among adults have involved men. The few studies among women have had methodological ambiguities. The authors conducted 2 experiments in the Israel Defense Forces to test the Pygmalion hypothesis among women. In both studies, the leaders were led to believe that the trainees randomly assigned to the Pygmalion condition had higher than usual potential. Experiment 1 tested the Pygmalion hypothesis among female officer cadets led by women. Although the treatment did raise expectations, none of the performance measures and none of the mediators or the moderators evidenced any expectancy effects. Experiment 2 tested the Pygmalion hypothesis among women and men taking the same course in gender-segregated platoons. The Pygmalion hypothesis was confirmed among men led by a man and among women led by a man but not among women led by a woman. The authors concluded that the Pygmalion effect can be produced among women but perhaps not by women. Pygmalion research among women leading men is now needed.