Kondo effect in coupled quantum dots with RKKY interaction: Finite temperature and magnetic field effects

We study transport through two quantum dots coupled by an RKKY interaction as a function of temperature and magnetic field. By applying the Numerical Renormalization Group (NRG) method we obtain the transmission and the linear conductance. At zero temperature and magnetic field, we observe a quantum phase transition between the Kondo screened state and a local spin singlet as the RKKY interaction is tuned. Above the critical RKKY coupling the Kondo peak is split. However, we find that both finite temperature and magnetic field restore the Kondo resonance. Our results agree well with recent transport experiments on gold grain quantum dots in the presence of magnetic impurities.Comment: 4 pages, 5 figure

Tunable Kondo screening in a quantum dot device

We consider electron transport along a single-mode channel which is in contact, via tunnel junctions in its walls, with two quantum dots. Electron tunneling to and from the dots contributes to the electron backscattering, and thus modifies the channel conductance. If the dots carry spin, the channel conductance becomes temperature dependent due to the Kondo effect. The two-dot device geometry allows for a formation of S=1 localized spin due to the indirect exchange interaction, called Ruderman-Kittel-Kasuya-Yosida interaction. This device offers a possibility to study the crossover between fully screened and under-screened Kondo impurity. We investigate the manifestation of such crossover in the channel conductance

Galveston Bay Oyster Studies, 1971

Galveston Bay oyster stocks were studied to detect changes which might affect the public reef oyster harvest. A mild winter and above normal salinity values favored increased disease (Labyrinthomyxa) incidence as well as increased predation from oyster drills (Thais) and stone crabs (Menippe). These factors resulted in annual death rates of 52% to 55% among older oysters groups. Oyster spat in an epidemic area were Labyrinthomyxa-infected by fall and suffered above normal mortality

Oyster Studies, 1970

Annual death rates among one to five year-old oyster stocks at tray stations in Galveston Bay ranged from 24 to 45%, representing an increase in mortality among the older stocks over that recorded in the previous year and an above average mortality for one-year old oysters. Labyrinthomyxa marina infections were primarily responsible

Summary of Oyster Studies Along the Texas Coast

The intensity of 1963 oyster (Crassostrea virginica) spat set was generally less than that observed in 1962. The set appeared to be more abundant along the lower coast than on the upper coast. A decline in apparent abundance of year old seed stock was noted, beginning in late spring. Unlike 1962 little increase in the abundance of seed oysters occurred during the fall

Oyster Studies, 1969

Oyster sampling was conducted in Galveston Bay, Texas. Monitoring of 1965, 1966, and 1967 year class oysters at two tray stations indicated a relatively low annual mortality rate of under 20%. Peak death rates, associated with Labyrinthomyxa infection, occurred in late summer. Moderate oyster spat setting occurred in the mid-bay area beginning in July. Survival was good and seed stock increased. Labyrinthomyxa marina infection among market oyster stocks remained below epidemic level and more oysters were available to the fishermen. Oystering was again centered in the mid-bay area and was judged to be relatively heavy. The harvest of 173,300 barrels was 22 percent higher than that of the previous season

Study of the Oyster (Crassostrea virginica) Population Along the Texas Coast

Reef sampling was continued in Galveston, Matagorda and San Antonio Bays to study trends in the oyster (Crassostrea Virginica) population. In Galveston a continued decline in spat and seed oyster stock occurred, with a lesser decline in market oyster stock. Matagorda Bay oyster stocks, which had suffered extensive mortality in 1964, showed only slight recovery. In San Antonio bay, the oyster population in the central bay, which had been decimated by disease in 1964, increased in abundance, but oyster stocks in the lower bay area diminished. Sring and late summer mortalities were common in all areas sampled. Generally, summer mortalities exceeded those in spring. Dermocystidium marinum infections were high in Galveston Bay but low, or negative, in other areas. The presence of ABO (Aransas Bay Organism) was suspected in Matagorda Bay and San Antonio Bay but was not confirmed. In spite of declining oyster stocks, the 1965-66 harvest set a new record of over four million pounds. As in past years, almost all of the harvest came from Galveston Bay

Survey of Oyster Diseases in the Galveston Bay Area - Survey of Oyster Populations and Associated Organisms

Moralities among tray-held oysters (Crassostrea virginica) were studied during a two year period at stations located on Switchover Reef and Hannah Reef. In 1963 moralities at both stations showed similar patterns, increasing during the summer months (with peaks in August-September) and declining during the fall and winter. The summer moralities were associated with high infections of Dermocystidium marinum. From March through December 1963 oysters at the Switch over station suffered a mortality of 52.6%. From April through December, 1963 a mortality of 42.2% occurred among the Hanna oysters

Study of the Oyster Population on Public Reefs in Galveston Bay during 1966

Public reefs in Galveston Bay and East Bay were sampled monthly to determine seasonal changes in oyster (Crassostrea virginica) stocks