arXiv subjects

A. P. Mills Jr.

Publications and source records attributed to A. P. Mills Jr..

5 recordsLinked to original sources

arXiv2006

Spin polarization induced tenfold magneto-resistivity of highly metallic 2D holes in a narrow GaAs quantum well

We observe that an in-plane magnetic field ($B_{||}$) can induce an order of magnitude enhancement in the low temperature ($T$) resistivity ($ρ$) of metallic 2D holes in a narrow (10nm) GaAs quantum well. Moreover, we show the first observation of saturating behavior of $ρ(B_{||})$ at high $B_{||}$ in GaAs system, which suggests our large positive $ρ(B_{||})$ is due to the spin polarization effect alone. We find that this tenfold increase in $ρ(B_{||})$ even persists deeply into the 2D metallic state with the high $B_{||}$ saturating values of $ρ$ lower than 0.1$\times$h/e$^2$. The dramatic effect of $B_{||}$ we observe on the highly conductive 2D holes (with $B$=0 conductivity as high as 75e$^2$/h) sets strong constraint on models for the spin dependent transport in dilute metallic 2D systems.

cond-mat.str-el↗

arXiv2005

Strongly Enhanced Hole-Phonon Coupling in the Metallic State of the Dilute Two-Dimensional Hole Gas

We have studied the temperature dependent phonon emission rate $P$($T$) of a strongly interacting ($r_s\geq$22) dilute 2D GaAs hole system using a standard carrier heating technique. In the still poorly understood metallic state, we observe that $P$($T$) changes from $P$($T$)$\sim T^5$ to $P$($T$)$\sim T^7$ above 100mK, indicating a crossover from screened piezoelectric(PZ) coupling to screened deformation potential(DP) coupling for hole-phonon scattering. Quantitative comparison with theory shows that the long range PZ coupling between holes and phonons has the expected magnitude; however, in the metallic state, the short range DP coupling between holes and phonons is {\it almost twenty times stronger} than expected from theory. The density dependence of $P$($T$) shows that it is {\it easier} to cool low density 2D holes in GaAs than higher density 2D hole systems.

cond-mat.str-el↗

arXiv2004

Temperature and Magnetic Field Enhanced Hall Slope of a Dilute 2D Hole System in the Ballistic Regime

We report the temperature($T$) and perpendicular magnetic field($B$) dependence of the Hall resistivity $ρ_{xy}(B)$ of dilute metallic two-dimensional(2D) holes in GaAs over a broad range of temperature(0.02-1.25K). The low $B$ Hall coefficient, $R_H$, is found to be enhanced when $T$ decreases. Strong magnetic fields further enhance the slope of $ρ_{xy}(B)$ at all temperatures studied. Coulomb interaction corrections of a Fermi liquid(FL) in the ballistic regime can not explain the enhancement of $ρ_{xy}$ which occurs in the same regime as the anomalous metallic longitudinal conductivity. In particular, although the metallic conductivity in 2D systems has been attributed to electron interactions in a FL, these same interactions should reduce, {\it not enhance} the slope of $ρ_{xy}(B)$ as $T$ decreases and/or $B$ increases.

cond-mat.str-el↗

arXiv2003

Fermi liquid behavior of metallic 2D holes at high temperatures

The resistivity $ρ$ of high mobility dilute 2D holes in GaAs exhibits a peak at a certain temperature $T^*$ in zero magnetic field($B$=0). In the $T>T^*$ regime where d$ρ$/d$T<$0, we observe for the first time both the $ν=1$ quantum Hall(QH) effect and a low field insulator-QH transition which is consistent with the 2D hole system being a Fermi liquid(FL). The known linear $T$-dependent conductivity in this $T$ regime then can be explained by hole-hole Coulomb interactions of this FL. The fact that the system is metallic (d$ρ$/d$T>$0) for $T<T^*$ implies that the high temperature FL transforms into the 2D metallic state in the neighborhood of $T^*$.

cond-mat.str-el↗

arXiv2001

Suppression of weak localization effects in low-density metallic 2D holes

We have measured the conductivity in a gated high-mobility GaAs two dimensional hole sample with densities in the range (7-17)x10^9 cm^-2 and at hole temperatures down to 5x10^-3 E_F. We measure the weak localization corrections to the conductivity g=G/(e^2/h) as a function of magnetic field (Delta g=0.019 +/- 0.006 at g=1.5 and T=9 mK) and temperature (d ln g/dT<0.0058 and 0.0084 at g=1.56 and 2.8). These values are less than a few percent of the value 1/pi predicted by standard weak localization theory for a disordered 2D Fermi liquid

cond-mat.str-el↗