Is it the boundaries or disorder that dominates electron transport in semiconductor `billiards'?

Semiconductor billiards are often considered as ideal systems for studying dynamical chaos in the quantum mechanical limit. In the traditional picture, once the electron's mean free path, as determined by the mobility, becomes larger than the device, disorder is negligible and electron trajectories are shaped by specular reflection from the billiard walls alone. Experimental insight into the electron dynamics is normally obtained by magnetoconductance measurements. A number of recent experimental studies have shown these measurements to be largely independent of the billiards exact shape, and highly dependent on sample-to-sample variations in disorder. In this paper, we discuss these more recent findings within the full historical context of work on semiconductor billiards, and offer strong evidence that small-angle scattering at the sub-100 nm length-scale dominates transport in these devices, with important implications for the role these devices can play for experimental tests of ideas in quantum chaos.Comment: Submitted to Fortschritte der Physik for special issue on Quantum Physics with Non-Hermitian Operator

On Overreaching, or Why Rick Perry May Save the Voting Rights Act but Destroy Affirmative Action

Abstract The State of Texas is presently staking out two positions that are not typically pursued by a single litigant. On the one hand, Texas is seeking the invalidation of the Voting Rights Act, and, on the other, the State is now defending the validity of the expansive race-based affirmative action policy it uses at its flagship university. This Essay presses the claim that Texas has increased the chance it will lose in both Texas v. Holder and Fisher v. University of Texas because it has opted to stake out markedly extreme positions in each. I argue that Texas would be more likely to succeed had it chosen to temper both its actions and claims in the pending cases. As it stands, Texas's assertive stance in Fisher promises to bolster the aversion many Justices already feel towards affirmative action. With regard to the VRA, however, Texas's uncompromising approach to the regime may prove to be the VRA's best defense. As recent redistricting and voter ID decisions suggest, Texas's stance may be provide what is arguably better evidence for why the statute remains necessary than anything proffered by the VRA's many supporters. Indeed, the State's aggressively hostile stance towards the VRA has the potential to destabilize judicial misgivings about the statute, and, if not fully reverse them, postpone their implementation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98443/1/elj%2E2012%2E1147.pd