Nuclear Spin Relaxation in Normal and Superconducting Aluminum. Magnetic-field-induced density of states in MgB 2: Spin susceptibility measured by conduction-electron spin resonance. Samples were sealed in quartz ampules under low pressure helium. This small peak is not due to magnetic field and is most probably a tiny conductivity coherence peak the analogue of the Hebel—Slichter peak which is known to be strongly suppressed by strong-coupling effects in alkali fullerides ,. The superconducting gap of in situ MgB 2 thin films by microwave surface impedance measurements.
Geometrical Barriers in High-Temperature Superconductors. Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB 2 samples. Figure shows the microwave cavity loss and cavity shift for a fine powder of MgB 2 and for two kinds of K 3C 60 samples: a single crystal and a fine powder as a function of temperature and for a few magnetic field values. It deals with the fundamentals of the interaction between microwaves and superconductors, and includes a basic description of how microwave devices can be constructed using these materials. We studied fine powder MgB 2 samples identical to batches in refs and. Superconductivity at 39 K in magnesium diboride.
Nuclear magnetic resonance of C 60 and fulleride superconductors. Somewhat better fits could be obtained when letting λ, ρ n, and B c2 differ from the mean literature values. For MgB 2, microwave measurements on compacted samples or surface impedance measurements supports this observation as therein no enhanced microwave absorption was observed ,,,,,. Two magnetic field data are shown for the crystal 0 and 1 T and three for the powder samples 0, 0. Magnetic field dependence of the microwave surface resistance in MgB 2 superconductors.
The powder samples were further ground together with non-conducting SnO 2 powder to prevent conducting links between the grains. Beyond Eliashberg superconductivity in MgB 2: Anharmonicity, two-phonon scattering, and multiple gaps. This may be related to the finite size and surface roughness of the single crystal sample. We observe an excess microwave loss or microwave absorption in small magnetic fields as low as a few % of the upper critical field, B c2 for a sample consisting of well-separated fine grains typical size is a few micrometers. The enhanced microwave loss appears progressively with increasing magnetic field additional data are shown in the Supplementary Material.
It is applied to calculate the microwave properties for two kinds of samples: when the electromagnetic field penetration is limited to the surface skin limit or when it fully penetrates into the fine grain samples penetration limit. The E-mail message field is required. The effects of σ 1 and σ 2 are decoupled for fine grains; for a sample placed in a microwave cavity, the loss is due to σ 1, whereas the resonance shift is due to σ 2 refs ,,. While the presence of a coherence peak itself is an interesting physical phenomenon ,, it is not relevant for the present discussion. Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering. Shedding light on topological superconductors. Microwave surface resistance of MgB 2.
The duplexer has a compact size of 41. Conductivity coherence factors in the conventional superconductors Nb and Pb. We discuss that the experimental observations for the crystal and fine powder K 3C 60 are explained well by these two regimes. The excess microwave absorption is not observable in a single crystal sample. Superconducting transmission lines -- 3. The origin of the anomalous superconducting properties of MgB 2.
Ultrasensitive hot-electron nanobolometers for terahertz astrophysics. It deals with the fundamentals of the interaction between microwaves and superconductors, and includes a basic description of how microwave devices can be constructed using these materials. The measured results at 73 K show a high performance. Upper-critical-field-temperature phase diagram of alkali-metal-intercalated C60 superconductors. The isolation between the two channels is better than 76 dB. Dc magnetic field dependence of the surface impedance in superconducting parallel plate transmission line resonators. Department of Energy by Iowa State University under Contract No.
The conductivity values are normalized by the normal state conductivity at the critical temperature. Although improved fits could be attained, we believe that the simplest model explains well the experimental observation of an enhanced microwave absorption. Conduction-electron spin resonance in the superconductor K 3C 60. Calculated real part and imaginary part of complex rf conductivity vs the reduced temperature for different values of the pinning force constant, κ p. Magnetic-field penetration depth in K 3C 60 measured by muon spin relaxation.