Extreme electron-hole drag and negative mobility in the Dirac plasma of graphene.

Coulomb drag between adjacent electron and hole gases has attracted considerable attention, being studied in various two-dimensional systems, including semiconductor and graphene heterostructures. Here we report measurements of electron-hole drag in the Planckian plasma that develops in monolayer graphene in the vicinity of its Dirac point above liquid-nitrogen temperatures. The frequent electron-hole scattering forces minority carriers to move against the applied electric field due to the drag induced by majority carriers.

Psychological Resilience of Mental Health Workers During the Russia-Ukraine War: Implications for Clinical Interventions.

To examine the prevalence and key correlates of psychological resilience in Ukrainian mental health workers (MHWs), using a novel discrepancy-based psychiatric resilience (DBPR) analytic approach. A total of 178 Ukrainian MHWs, recruited via convenience sampling from July to August 2023, completed a survey assessing their war-related exposures, occupational stress, and mental health symptoms and sociodemographic and psychosocial characteristics. DBPR scores were computed by regressing composite distress scores onto measures of war- and work-related stressors.

Kagome Quantum Oscillations in Graphene Superlattices.

Electronic spectra of solids subjected to a magnetic field are often discussed in terms of Landau levels and Hofstadter-butterfly-style Brown-Zak minibands manifested by magneto-oscillations in two-dimensional electron systems. Here, we present the semiclassical precursors of these quantum magneto-oscillations which appear in graphene superlattices at low magnetic field near the Lifshitz transitions and persist at elevated temperatures. These oscillations originate from Aharonov-Bohm interference of electron waves following open trajectories that belong to a kagome-shaped network of paths characteristic for Lifshitz transitions in the moire superlattice minibands of twistronic graphenes.

Giant magnetoresistance of Dirac plasma in high-mobility graphene.

The most recognizable feature of graphene's electronic spectrum is its Dirac point, around which interesting phenomena tend to cluster. At low temperatures, the intrinsic behaviour in this regime is often obscured by charge inhomogeneity but thermal excitations can overcome the disorder at elevated temperatures and create an electron-hole plasma of Dirac fermions. The Dirac plasma has been found to exhibit unusual properties, including quantum-critical scattering and hydrodynamic flow.