Energy relaxation during hot-exciton transport in quantum wells: Direct observation by spatially resolved phonon-sideband spectroscopy

We investigate the energy relaxation of excitons during the real-space transport in ZnSe quantum wells by using microphotoluminescence with spatial resolution enhanced by a solid immersion lens. The spatial evolution of the LO-phonon sideband, originating from the LO-phonon assisted recombination of hot excitons, is measured directly. By calculating the LO-phonon assisted recombination probability, we obtain the nonthermal energy distribution of excitons and observe directly the energy relaxation of hot excitons during their transport. We find the excitons remain hot during their transport on a length scale of several micrometers. Thus, the excitonic transport on this scale cannot be described by classical diffusion.Comment: 4 pages, 4 figure

A spintronic source of circularly polarized single photons

We present a spintronic single photon source which emits circularly polarized light, where the helicity is determined by an applied magnetic field. Photons are emitted from an InGaAs quantum dot inside an electrically operated spin light-emitting diode, which comprises the diluted magnetic semiconductor ZnMnSe. The circular polarization degree of the emitted light is high, reaching 83% at an applied magnetic field of 2T and 96% at 6 T. Autocorrelation traces recorded in pulsed operation mode prove the emitted light to be antibunched. The two circular polarization states could be used for representing quantum states |0> and |1> in quantum cryptography implementations

Hot exciton transport in ZnSe quantum wells

The in-plane transport of excitons in ZnSe quantum wells is investigated directly by microphotoluminescence in combination with a solid immersion lens. Due to the strong Froehlich coupling, the initial kinetic energy of the excitons is well controlled by choosing the excess energy of the excitation laser. When increasing the laser excess energy, we find a general trend of increasing transport length and more importantly a pronounced periodic quenching of the transport length when the excess energy corresponds to multiples of the LO-phonon energy. Such features show the dominant role of the kinetic energy of excitons in the transport process. Together with the excitation intensity dependence of the transport length, we distinguish the phonon wind driven transport of cold excitons and defect-limited hot exciton transport.Comment: 4 pages, 4 figure

The US law permitting permanent expatriates to vote in federal elections needs to be placed on a sturdier constitutional footing

US Citizens have a right to vote in federal elections in their former states even if they have permanently left the country. Brian Kalt argues that this right, and the Uniformed and Overseas Citizens Absentee Voting Act from which it flows, has constitutional problems given that those who have left are no longer ‘people of the state’. He writes that Congress cannot simply rewrite states’ voter-eligibility requirements as it pleases. He suggests that to address the problem, Congress could establish territory-style representation in the form of non-voting House delegates or piggyback reforms on to the proposed National Popular Vote Interstate Compact

Swearing in the Phoenix: Toward a More Sensible System for Seating Members of the House of Representatives at Organization

Under U.S. House precedent, any member-elect can challenge the right of any other member-elect to take the oath of office at the beginning of a new term. The uncontested members-elect then swear in and decide the fate of those who were forced to stand aside. If the House is closely divided and there are disputed elections at the margins, a minority party could exploit this procedure to try to seize control of the House. This would be outrageous and damaging, even if the effort failed. Contending for ultimate control, both sides could level motions, appeals, and tit-for-tat pre-oath challenges. The proto-House would degenerate into a chaotic mass of votes, meta-votes (about who gets to vote), and meta-meta-votes before anyone has even been sworn in. Instead of the House being controlled by the party that won the most seats in the election, it might go instead to the party that is most disciplined and unified-or, failing that, to the party that is more adept at parliamentary machinations. This nightmare is not completely hypothetical; the House once witnessed a power grab much like this-and it succeeded. But even an unsuccessful attempt could worsen the national partisan divide, weaken the House's legitimacy, and threaten the House's already dangerously low levels of comity. So could an attempt by a majority to bolster its advantage by a seat or two

Presidential Impeachment and Removal: From the Two-Party System to the Two-Reality System

mpeachment is not the most quotable of subjects, but in April 1970, House Minority Leader Gerald Ford managed to make it so. Spearheading a doomed attempt to impeach Supreme Court Justice William 0. Douglas, Ford famously said that an impeachable offense is "whatever a majority of the House of Representatives considers to be at a given moment in history," adding that "conviction results from whatever ... two-thirds of the [Senate] considers to be sufficiently serious to require removal of the accused from office."' This idea is sometimes rendered more simply as "impeachment is whatever the House of Representatives says it is, and removal is whatever the Senate says it is."2 Ford's statement has garnered plenty of criticism over the decades, because it seemingly ignores the Constitution's definition of impeachable offenses-high crimes and misdemeanors ("HCMs")-and substitutes Congress's political whim.

Humboldt Bay power plant canal remediation

Application No. 9A13A062