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UID:6acf9525cf5b3
DTSTART:20261020T090000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20261020T100000Z
LOCATION:Elements Room
SUMMARY:ICFO | LEONID PONOMARENKO
CLASS:PUBLIC
DESCRIPTION:I will discuss two distinct transport phenomena in high-mobilit
 y monolayer graphene. The first concerns the Dirac electron&ndash\;hole pl
 asma that forms near charge neutrality at elevated temperatures. Analysis 
 of longitudinal and Hall resistivities reveals strong Coulomb drag: majori
 ty carriers pull minority carriers along with them\, reversing their expec
 ted drift direction and producing negative mobility. I will discuss the co
 mpetition between electron&ndash\;hole collisions and scattering by phonon
 s and impurities\, and its implications for a hydrodynamic description of 
 the Dirac plasma.The second part will present unpublished experiments on n
 onlinear transport in the low-temperature Shubnikov&ndash\;de Haas regime.
  Maps of differential resistivity versus carrier density and DC Hall volta
 ge reveal diamond-shaped regions of low resistance\, termed Landau diamond
 s\, and a bias-induced reversal of the oscillation phase. Measurements on 
 devices of different widths support the Hall voltage as the controlling pa
 rameter in this experiment. I will discuss an interpretation based on the 
 tilting and overlap of Landau bands in the Hall electric field and the use
  of diamond boundaries to estimate Landau-level spacings.
DTSTAMP:20261014T144349Z
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