Anomalous High-Temperature Magnetoresistance in a Dilute 2D Hole System.

We report an unusual magnetoresistance that strengthens with the temperature in a dilute two-dimensional (2D) hole system in GaAs/AlGaAs quantum wells with densities p=1.98-0.99×10^{10}/cm^{2} where r_{s}, the ratio between Coulomb energy and Fermi energy, is as large as 20-30. We show that, while the system exhibits a negative parabolic magnetoresistance at low temperatures (≲0.4 K) characteristic of an interacting Fermi liquid, a positive magnetoresistance emerges unexpectedly at higher temperatures, and grows with increasing temperature even in the regime T∼E_{F}, close to the Fermi energy. This unusual positive magnetoresistance at high temperatures can be attributed to the viscous transport of 2D hole fluid in the hydrodynamic regime where holes scatter frequently with each other. These findings give insight into the collective transport of strongly interacting carriers in the r_{s}≫1 regime and new routes toward magnetoresistance at high temperatures.

Interfacial Charge Transfer and Gate-Induced Hysteresis in Monochalcogenide InSe/GaSe Heterostructures.

Heterostructures of two-dimensional (2D) van der Waals semiconductor materials offer a diverse playground for exploring fundamental physics and potential device applications. In InSe/GaSe heterostructures formed by sequential mechanical exfoliation and stacking of 2D monochalcogenides InSe and GaSe, we observe charge transfer between InSe and GaSe because of the 2D van der Waals interface formation and a strong hysteresis effect in the electron transport through the InSe layer when a gate voltage is applied through the GaSe layer. A gate voltage-dependent conductance decay rate is also observed. We relate these observations to the gate voltage-dependent dynamical charge transfer between InSe and GaSe layers.