We report a nonsaturating linear magnetoresistance in charge-compensated bilayer graphene in a temperature range from 1.5 to 150 K. The observed linear magnetoresistance disappears away from charge neutrality, ruling out the traditional explanation of the effect in terms of the classical random resistor network model. We show that experimental results qualitatively agree with a phenomenological two-fluid model taking into account electron-hole recombination and finite-size sample geometry.

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We report strong narrowband stimulated far-infrared cyclotron-resonance emission from the light holes in germanium in crossed electric and magnetic fields. The emission spectrum consists of a single line which is linearly tunable with magnetic field. The gain of the cyclotron-resonance laser is determined to be 0.05 ± 0.02 cm -1 . For the first time we have identified the lasing transition to be the n -2 to n ™ 1 Landau-level transition of the 6-set light holes by a comparison of absorption and emission spectra with calculations of the band structure including nonparabolicity corrections.

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We report the terahertz photoconductivity in a meander-shaped epitaxial graphene sample. The measurements at wavelengths 280, 148, and 90 μm (frequencies of 1.07, 2.03, and 3.32 THz) demonstrate that the photoconductivity is independent on the wavelength and is related to bolometric heating under the condition of weak localization enhanced due to long sample boundaries.

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