Role of anion size, magnetic moment, and disorder on the properties of the organic conductor kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}

Shubnikov-de Haas and angular dependent magnetoresistance oscillations have been used to explore the role of anion size, magnetic moment, and disorder in the organic conductors kappa-(BETS)_2GaBr_{4} and kappa-(BETS)_2FeCl_{2}_Br_{2} in the isomorphic class kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}. The results, combined with previous work, show correlations between the anion composition (Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}) and the superconducting transition temperature, effective mass, Fermi surface topology, and the mean free path.Comment: 5 pages, 6 figure

Kemitraan Pemerintah dan Swasta dalam Pembangunan Bandara Swadaya Sangia Nibandera Kabupaten Kolaka

Penelitian ini bertujuan menjelaskan konsep kemitraan dalam pembangunan bandara Swadaya di Kabupaten Kolaka, dengan melihat dari mekanisme, struktur dan insentif dari kemitraan.Metode yang digunakan adalah metode kualitatif deskriptif. Data dianalisis dengan reduksi data, penyajian data, dan menarik kesimpulan.Hasil Penelitian ini menunjukkan bahwa dari pelaksanaan kemitraan antara Pemerintah Kabupaten Kolaka dan Swasta dalam Pembangunan Bandar Udara Swadaya Sangia Nibandera di Kabupaten Kolaka diihat dari mekanisme, struktur dan insentif terlaksana dengan baik dan efektif. Dari pelaksanaan kemitraan ini memberikan manfaat bagi masyarakat Kabupaten Kolaka dengan meningkatnya pendapatan dan juga memudahkan masuknya Investor di Kabupaten Kolaka

Superconductivity in an organic insulator at very high magnetic fields

We investigate by electrical transport the field-induced superconducting state (FISC) in the organic conductor $\lambda$-(BETS)$_2$FeCl$_4$. Below 4 K, antiferromagnetic-insulator, metallic, and eventually superconducting (FISC) ground states are observed with increasing in-plane magnetic field. The FISC state survives between 18 and 41 T, and can be interpreted in terms of the Jaccarino-Peter effect, where the external magnetic field {\em compensates} the exchange field of aligned Fe$^{3+}$ ions. We further argue that the Fe$^{3+}$ moments are essential to stabilize the resulting singlet, two-dimensional superconducting stateComment: 9 pages 3 figure

Magnetic-field-induced superconductivity in layered organic molecular crystals with localized magnetic moments

The synthetic organic compound lambda-(BETS)2FeCl4 undergoes successive transitions from an antiferromagnetic insulator to a metal and then to a superconductor as a magnetic field is increased. We use a Hubbard-Kondo model to clarify the role of the Fe(3+) magnetic ions in these phase transitions. In the high-field regime, the magnetic field acting on the electron spins is compensated by the exchange field He due to the magnetic ions. This suggests that the field-induced superconducting state is the same as the zero-field superconducting state which occurs under pressure or when the Fe(3+) ions are replaced by non-magnetic Ga(3+) ions. We show how He can be extracted from the observed splitting of the Shubnikov-de Haas frequencies. Furthermore, we use this method of extracting He to predict the field range for field-induced superconductivity in other materials.Comment: 5 page

The High Magnetic Field Phase Diagram of a Quasi-One Dimensional Metal

We present a unique high magnetic field phase of the quasi-one dimensional organic conductor (TMTSF)$_2$ClO$_4$. This phase, termed "Q-ClO$_4$", is obtained by rapid thermal quenching to avoid ordering of the ClO$_4$ anion. The magnetic field dependent phase of Q-ClO$_4$ is distinctly different from that in the extensively studied annealed material. Q-ClO$_4$ exhibits a spin density wave (SDW) transition at $\approx$ 5 K which is strongly magnetic field dependent. This dependence is well described by the theoretical treatment of Bjelis and Maki. We show that Q-ClO$_4$ provides a new B-T phase diagram in the hierarchy of low-dimensional organic metals (one-dimensional towards two-dimensional), and describe the temperature dependence of the of the quantum oscillations observed in the SDW phase.Comment: 10 pages, 4 figures, preprin

Experimental study on compressive strength and infiltration rate of pervious concrete containing recycled coarse aggregate and seawater

In this study, pervious concrete specimens were created containing 100 percent of Recycled Coarse Aggregate (RCA) as a replacement for Natural Coarse Aggregate (NCA) and seawater as a replacement for Fresh Water (FW). Eighteen specimen tests in total were prepared which consisted of nine specimens containing Recycled Coarse Aggregate Seawater (RCAS) concrete and nine specimens containing Recycled Coarse Aggregate Fresh-water (RCAF) as control concrete. Both water to cement ratio of 0.45 and RCA to cement ratio of 0.25 is determined and the mix design is calculated. Fresh concrete was cast on the cylindrical mold of 150 x 300mm in a porous formation. Then the compressive strength and infiltration rate tests were conducted to understand the performance of RCA mixed seawater (SW) at curing times of 3, 7, and 28 days. The results show that the compressive strength of RCAS can reach a peak of around 8.98 MPa compared with RCAF just around 7.27 MPa in maximum curing of 28 days and the value of RCAS samples shows that the infiltration rate is increasing linearly as compressive strength is from three days to 28 days

Phase Diagram of Pressure-Induced Superconductivity in EuFe2As2 Probed by High-Pressure Resistivity up to 3.2 GPa

We have constructed a pressure$-$temperature ($P-T$) phase diagram of $P$-induced superconductivity in EuFe$_2$As$_2$ single crystals, via resistivity ($\rho$) measurements up to 3.2 GPa. As hydrostatic pressure is applied, an antiferromagnetic (AF) transition attributed to the FeAs layers at $T_\mathrm{0}$ shifts to lower temperatures, and the corresponding resistive anomaly becomes undetectable for $P$ $\ge$ 2.5 GPa. This suggests that the critical pressure $P_\mathrm{c}$ where $T_\mathrm{0}$ becomes zero is about 2.5 GPa. We have found that the AF order of the Eu$^{2+}$ moments survives up to 3.2 GPa without significant changes in the AF ordering temperature $T_\mathrm{N}$. The superconducting (SC) ground state with a sharp transition to zero resistivity at $T_\mathrm{c}$ $\sim$ 30 K, indicative of bulk superconductivity, emerges in a pressure range from $P_\mathrm{c}$ $\sim$ 2.5 GPa to $\sim$ 3.0 GPa. At pressures close to but outside the SC phase, the $\rho(T)$ curve shows a partial SC transition (i.e., zero resistivity is not attained) followed by a reentrant-like hump at approximately $T_\mathrm{N}$ with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like strain component is applied using a solid pressure medium, the partial superconductivity is continuously observed in a wide pressure range from 1.1 GPa to 3.2 GPa.Comment: 7 pages, 6 figures, accepted for publication in Physical Review B, selected as "Editors' Suggestion

The Fulde-Ferrell-Larkin-Ovchinnikov State in the Organic Superconductor k-(BEDT-TTF)2Cu(NCS)2 as Observed in Magnetic Torque Experiments

We present magnetic-torque experiments on the organic superconductor k-(BEDT-TTF)2Cu(NCS)2 for magnetic fields applied parallel to the 2D superconducting layers. The experiments show a crossover from a second-order to a first-order transition when the upper critical field reaches 21 T. Beyond this field, which we interpret as the Pauli limit for superconductivity, the upper critical field line shows a pro-nounced upturn and a phase transition line separates the superconducting state into a low- and a high-field phase. We interpret the data in the framework of a Fulde-Ferrell-Larkin-Ovchinnikov state.Comment: 2 pages, 1 figur

Fiber-coupled Antennas for Ultrafast Coherent Terahertz Spectroscopy in Low Temperatures and High Magnetic Fields

For the purposes of measuring the high-frequency complex conductivity of correlated-electron materials at low temperatures and high magnetic fields, a method is introduced for performing coherent time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed magnets. Miniature fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 1.5 Kelvin and up to 17 Tesla, for eventual use in higher-field magnets. Maintaining the sub-micron alignment between fiber and antenna during thermal cycling, obtaining ultrafast (${<200}$~fs) optical gating pulses at the end of long optical fibers, and designing highly efficient devices that work well with low-power optical gating pulses constitute the major technical challenges of this project. Data on a YBCO superconducting thin film and a high mobility 2D electron gas is shown.Comment: 8 pages, 9 figure