Hot-hole effects in a dilute two-dimensional gas in SiGe

Abstract

We study the resistivity vs. electric-field dependence ρ(E) of a dilute twodimensional hole (h) system in SiGe, on both sides of the crossover from weak to strong localization at B = 0. Using ρ as a "thermometer" to obtain the effective temperature of the holes Te(E), we find that ρ(E) can be attributed to hole heating. In spite of the strong localization and h-h interactions, the power loss does not indicate any deviation from the density and temperature dependences predicted assuming independent and delocalized electrons. The consequences of these results on the h-h interaction assisted hopping, glassy behaviour and E-field scaling are developed. The hole-phonon coupling involves a limited screening, a deformation potential compatible with measurements at larger densities and temperatures, and a piezoelectric component which is definitely probed.

Energy loss rates of hot Dirac fermions in epitaxial, exfoliated, and CVD graphene

“…20) and SiGe (Ref. 19) where good agreement between the two methods was found when SdH oscillations below 1 T were analyzed. We attribute this to a magnetic-field suppression of the energy loss rate, as the WL method measures the energy loss rate near 0 T, whereas the relatively low mobilities in most graphene samples require the SdH method to make measurements at much higher fields, typically 10 to 18 T in our samples, where the Landau quantization energy is 30 to 50 meV and significant changes in the current distribution also occur.…”

“…[18][19][20][21][22] The energy loss rates were determined as a function of carrier temperature by measuring the amplitudes of the SdH oscillations as a function of current (Fig. 4).…”

“…[19][20][21][22] In GaAs, 20 good agreement was found between the values for electron temperature deduced from the WL peak and SdH oscillations at low fields (∼0.5 T) up to ∼4 K. Similarly excellent agreement was found for the two methods in SiGe (Ref. 19) but they could only be studied for electron temperatures up to 1.1 K. In our work the WL peak persists up to temperatures of almost 100 K, allowing a much more extensive range of parameters to be studied. Previous work in graphene, 26 however, was not able to determine energy loss rates from the damping of the WL peak.…”

Universal scaling in disordered systems and nonuniversal exponents

“…The hot electron model in the WL regime 6 (HEM-WL) does not involve any exchange of energy between the sample and the substrate at low temperatures but explains the characteristic logarithmic field-dependence of conductance. The electron heating effects have been shown to account for the nonlinear conductance also in the SL regime of a 2D system 7,8 but with a provision of exchanging energy between the sample and the substrate. The nonOhmic resistance in the SL regime is still described by the equation (Eq.…”

A method for measuring the nonlinear response in dielectric spectroscopy through third harmonics detection

“…Understanding nonlinear effects allowed decisive breakthrough in condensed matter physics. Spin glasses [1,2,3,4,5,6], ferroelectric, freezing, or dipolar glass transitions [7,8,9,10,11,12,13,14,15,16,17,18,19], isotropic-liquid crystal transition [20,21] or binary mixtures [22,23], superconductivity [24,25,26,27,28,29], field [30,31,32,33,34] or heating [35,36,37,38,39,40] effects in electrical transport, heating due to electric field excitation of supercooled liquids [41,42] are a few among many topics where non linear measurements have proven to be a precious tool.…”