Rösslhuber, R., Rose, E., Ivek, T., Pustogow, A., Breier, T., Geiger, M., … Dressel, M. (2018). Structural and Electronic Properties of (TMTTF)2X Salts with Tetrahedral Anions. Crystals, 8(3), 121. https://doi.org/10.3390/cryst8030121
Comprehensive measurements of the pressure- and temperature-dependent dc-transport are combined with dielectric spectroscopy and structural considerations in order to elucidate the charge and anion orderings in the quasi-one-dimensional charge-transfer salts (TMTTF) 2 X with non-centrosymmetric anions X = BF 4 , ClO 4 and ReO 4 . Upon applying hydrostatic pressure, the charge-order transition is suppressed in all three compounds, whereas the influence on the anion order clearly depends on the particular compound. A review of the structural properties paves the way for understanding the effect of the anions in their methyl cavities on the ordering. By determining the complex dielectric constant ϵ ^ ( ω , T ) in different directions we obtain valuable information on the contribution of the anions to the dielectric properties. For (TMTTF) 2 ClO 4 and (TMTTF) 2 ReO 4 , ϵ b ′ exhibits an activated behavior of the relaxation time with activation energies similar to the gap measured in transport, indicating that the relaxation dynamics are determined by free charge carriers.
Pinterić, M., Rivas Góngora, D., Rapljenović, Ž., Ivek, T., Čulo, M., Korin-Hamzić, B., … Tomić, S. (2018). Electrodynamics in Organic Dimer Insulators Close to Mott Critical Point. Crystals, 8(5), 190. https://doi.org/10.3390/cryst8050190
Organic layered charge-transfer salts κ -(BEDT-TTF) 2 X form highly frustrated lattices of molecular dimers in which strong correlations give rise to Mott insulating states situated close to the metal-to-insulator phase boundary. The salts κ -(BEDT-TTF) 2 Cu 2 (CN) 3 and κ -(BEDT-TTF) 2 Ag 2 (CN) 3 have been considered as prime candidates for a quantum spin liquid, while κ -(BEDT-TTF) 2 CuN(CN) 2 Cl has been suggested as a prototypical charge-order-driven antiferromagnet. In this paper, we summarize and discuss several key results, including some not reported previously, obtained in search to clarify the competition of these two ground states. The origin of anomalous dielectric response found at low temperatures in all three salts is also discussed. We conclude by pointing out the relevant new insights into the role of frustration and random disorder in the suppression of magnetic ordering and formation of the spin liquid state.
Wollandt, T., Thiemann, M., Dressel, M., & Scheffler, M. (2018). Superconducting stripline resonators at frequencies up to 50 GHz for microwave spectroscopy applications. Journal of Physics: Conference Series, 969(1), 012082. Retrieved from http://stacks.iop.org/1742-6596/969/i=1/a=012082
Planar superconducting microwave resonators are commonly operated for various cryogenic applications, typically at frequencies between 2 and 15 GHz. But for certain applications, e.g. microwave spectroscopy to study the dynamics of charges and spins in solids, a wider spectral range is desired. Driving such microwave resonators at higher frequencies is challenging due to enhanced losses and reduced wavelength. Here we present superconducting stripline resonators operating at multiple frequencies as high as 50 GHz. These resonators are fabricated of Pb and can easily be adjusted to particular applications, including mK temperatures in a dilution refrigerator. Demonstrating such a resonator as a spectroscopic tool, we detect the superconducting transition of a Sn sample in a wide spectral range.
Urna, B., Laurent, H., & Matthias, K. (2018). Extrapolation to Nonequilibrium from Coarse-Grained Response Theory. Phys. Rev. Lett., 120(123), 180604. https://doi.org/https://doi.org/10.1103/PhysRevLett.120.180604
Bondorf, L., Beutel, M., Thiemann, M., Dressel, M., Bothner, D., Sichelschmidt, J., … Scheffler, M. (2018). Angle-dependent electron spin resonance of YbRh2Si2 measured with planar microwave resonators and in-situ rotation. Physica B: Condensed Matter, 536, 331–334. https://doi.org/10.1016/j.physb.2017.10.046
Bothner, D., Clauss, C., Koroknay, E., Kemmler, M., Gaber, T., Jetter, M., … Kleiner, R. (2012). Reducing vortex losses in superconducting microwave resonators with microsphere patterned antidot arrays. Applied Physics Letters, 100(1), 012601. https://doi.org/10.1063/1.3673869
Zornoza, P., Petukhov, K., Dressel, M., Biskup, N., Vuletić, T., & Tomić, S. (2005). Anisotropy and field-dependence of the spin-density-wave dynamics in the quasi one-dimensional conductor (TMTSF)2PF6. Eur. Phys. J. B, 46(2), 223–230. https://doi.org/10.1140/epjb/e2005-00223-3
Mukhin, A. A., Prokhorov, A. S., Gorshunov, B. P., Zvezdin, A. K., Travkin, V. D., & Dressel, M. (2002). Submillimeter spectroscopy of electron transitions and the macroscopic quantum tunneling of magnetization in molecular nanoclusters. Physics-Uspekhi, 45(11), 1186–1191. https://doi.org/10.1070/pu2002v045n11abeh001209
Aichele, N., Gommel, U., Laßmann, K., Maier, F., Zeller, F., Haller, E. E., … Müssig, H. (1997). Isotopic Shifts of the Rotational States of Interstitial Oxygen in Germanium. In Proc. of the 19th Int. Conf. on Defects in Semiconductors (p. 258).
Lunkenheimer, P., Dressel, M., Gorshunov, B. P., Schneider, U., Schiener, B., Böhmer, R., & Loidl, A. (1997). Dielectric Spectroscopy at High Frequencies on Glass Forming Liquids. Mater. Res. Soc. 455: 47, 455, 47.
Degiorgi, L., Thieme, S., Ott, H. R., Dressel, M., Grüner, G., Dalichaouch, Y., … F. Steglich, F. (1997). The electrodynamic response of heavy-electron materials with magnetic phase transitions. Z. Phys. B, 102(3), 367–380.
Petersen, J., Strohmaier, R., Gompf, B., & Eisenmenger, W. (1997). Monolayers of tetrachloro-thioindigo and thioindigo in the STM: orientational disorder and the absence of photochromism. Surface Science, 389(1–3), 329–337. https://doi.org/10.1016/s0039-6028(97)00446-9
Dressel, Martin, Grüner, G., Eldridge, J. E., & Williams, J. M. (1997a). Optical properties of organic superconductors. Synthetic Metals, 85(1–3), 1503–1508. https://doi.org/10.1016/s0379-6779(97)80325-6
Donovan, S., Dressel, M., Degiorgi, L., Schwartz, A., Virosztek, A., & Grüner, G. (1997). Electrodynamic properties of (TMTSF)2PF6. Synthetic Metals, 86(1–3), 2181–2182. https://doi.org/10.1016/s0379-6779(97)81086-7
Dressel, Martin, Grüner, G., Eldridge, J. E., & Williams, J. M. (1997b). Optical properties of organic superconductors. Synthetic Metals, 85(1–3), 1503–1508. https://doi.org/10.1016/s0379-6779(97)80325-6