Influence of magnetic field on the electronic specific heat of the organic metal (BEDT-TTF)2KHg(SCN)4

Specific heat measurements of a single crystal of the organic metal (BEDT-TTF)₂KHg(SCN)₄ have been carried out at low temperatures and under a magnetic field of up to 14 T. A jump in the specific heat of about 0.1 J/mol·K, which corresponds to the antiferromagnetic phase transition, has been observed. The magnetic field is found to decrease the transition temperature at any field orientation. The strongest effect was found to take place in the field direction along the highly conducting ac plane. Zh. éksp. Teor. Fiz. 113, 1058–1063 (March 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Frequency-shifting submillimeter single-sideband receiver

A single sideband (SSB) receiver has been developed and implemented for use with a submillimeter sideband generator. While the sideband generator emits both an upper and lower sideband, and even some unshifted laser radiation, the receiver responds to only one sideband. The operator of the system can choose which sideband to receive. Rejection of the undesired signal is accomplished through selective frequency shifting coupled with the use of a commercially available single-sideband microwave mixer.     

Investigation of electron lifetimes in molybdenum with dilute substitutional impurities

We have measured the electronic lifetimes of the systems Mo(W), Mo(Ru), Mo(Fe) and Mo(U). The concentrations were ≈ 370PPM, 70PPM, 20PPM, and 50PPM respectively. For the first three systems, only the hole octahedron centered atH was investigated thoroughly for all angles and the data inverted to get point lifetimes. For Mo(U) the investigation was done over the entire Fermi surface with the aid of an on-line PDP 11/20 mini-computer. Only selective points were used on other pieces of the Fermi surface in order to avoid problems with degenerate frequencies. A careful determination of the effective masses was also made at all angles under investigation. The masses were found to be in disagreement with those of Leaver and Meyers (these masses were used in our orginal investigation) by as much as 20% in some orientations. The electronic lifetimes were nearly isotropic on the hole octahedron in all the alloy systems investigated. In Mo(U) the isotropy was found to extend to all thed-like surfaces. Only thes-p-like hole ellipsoids centered atN possibly have a substantially different lifetime, but its measurement is inaccurate due to beats from degenerate and many close-lying frequencies.     

An application of theta functions to the band problem

The utility of theta function-modulated plane wave bases — the modulation is essentially by site-centered Gaussians — in the band problem is shown. The Kronig-Penney model is used as a test system.     

Positron lifetimes in five phases of BEA

Positron lifetimes have been measured as a function of temperature in 4-butyloxybenzal-4′-ethylaniline (BEA). BEA has been previously reported to have two liquidcrystalline phases (smectic and nematic) with transition temperatures as follows: solid → smectic, 40.5° C; smectic → nematic, 51.0° C; and nematic → isotropic liquid, 65.5° C. Positron life time spectra were resolved into two components, with the shorter component τ₁ remaining approximately constant in all phases, and τ₂ exhibiting reversible changes at all of the above transitions. In addition, an irreversible discontinuity in the τ₂ lifetime was observed in the vicinity of 28° C, indicating the presence of a new phase (phase X) of BEA. The τ₂ andI ₂ values obtained for the various phases of BEA are: solid (1.25 nsec, 7.1%), phase X (1.97 nsec, 26.2%), smectic (2.36 nsec, 23.6%), nematic (2.72 nsec, 28.3%), and isotropic liquid (2.69 nsec, 29.8%).