M.V. Kartsovnik

Resistance and magnetoresistance anomaly in a new stable organic metal (ET)2TlHg(SCN)4

Abstract A new organic metal (ET) 2 TlHg(SCN) 4 has been synthesized. The X-ray study shows the compound to be isostructural to (ET) 2 MHg(SCN) 4 salts with M = K, NH 4 and Rb. The resistance and magnetoresistance measurements show anomalous behaviour at low temperature which may be attributed to spin-density-wave instability. Shubnikov-de Haas oscillations have also been observed at low temperature.

Transport properties and giant Shubnikov-de Haas oscillations in the first organic conductor with metal complex anion containing selenocyanate ligand, (ET)2 T1Hg(SeCN)4

Abstract Temperature dependence of the resistivity in various crystallographic directions and high pulsed field magnetoresistance of organic metal α-(ET) 2 TlHg(SeCN) 4 have been studied at temperatures down to 80 mK. Giant Shubnikov-de Haas oscillations, which are attributed to the two-dimensional nature of the cylindrical Fermi surface with a very small warping along the direction of the lowest conductivity have been observed. Four harmonics of the fast oscillations with fundamental frequency F 0 = 653 ± 3 T and slow frequency oscillations with F s = 38 ± 5 T have been revealed.

Nonlinear conductivity in the ground state of α-(BEDT-TTF)2KHg(SCN)4

We have studied the current-voltage characteristics of α-(BEDT-TTF) 2 KHg(SCN) 4 in the low temperature state. For the conductivity parallel to the conducting ac plane the nonlinearity appears above a well defined finite threshold electric field of 25 mV/cm at 2 K. This threshold field increases to about 200 mV/cm at 7.5 K. The nonlinearity is not detected above T = 8 K. Our data clearly show that the low temperature phase of α-(BEDT-TTF) 2 KHg(SCN) 4 is a density wave.

The angular-dependent magnetoresistance in α-(BEDT-TTF)2KHg(SCN)4

In spite of extensive experimental studies of the angular-dependent magnetoresistance (ADMR) of the low-temperature phase (LTP) of α-(BEDT-TTF)2 KHg(SCN)4 about a decade ago, the nature of LTP remains elusive. Here we present a new study of ADMR of LTP in α-(ET)2 salts assuming that LTP is unconventional charge density wave (UCDW). In the presence of magnetic field the quasi-particle spectrum in UCDW is quantized, which gives rise to striking ADMR in UCDW. The present model appears to account for many existing ADMR data of α-(BEDT-TTF)2 KHg(SCN)4 remarkably well.

Unconventional Charge-Density Wave in the Organic Conductor α-(BEDT-TTF)2KHg(SCN)4

The low temperature phase (LTP) of alpha-(BEDT-TTF)2KHg(SCN)(4) salt is known for its surprising angular dependent magnetoresistance (ADMR), which has been studied intensively in the last decade. However, the nature of the LTP has not been understood until now. Here we analyze theoretically ADMR in unconventional (or nodal) charge-density wave (UCDW). In magnetic field the quasiparticle spectrum in UCDW is quantized, which gives rise to spectacular ADMR. The present model accounts for many striking features of ADMR data in alpha-(BEDT-TTF)2KHg(SCN)(4).

Magnetic transformations in the organic conductorκ-(BETS)2Mn[N(CN)2]3at the metal-insulator transition

O. M. Vyaselev, M. V. Kartsovnik, W. Biberacher, L. V. Zorina, N. D. Kushch, and E. B. Yagubskii Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow region, 142432, Russia Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow region, 142432, Russia (Dated: November 29, 2010)

Interlayer magnetotransport in κ-(BEDT-TTF)2X superconductors

Interlayer magnetotransport of κ-(BEDT-TTF)2X with X=Cu(NCS)2 is analysed from the viewpoint of the layered character of superconductivity. The current-voltage characteristics suggest that the Josephson coupling occurs via normal metal layers, i.e. it is of the SNS rather than tunnel type. The extreme anisotropy enhances the normal density-of-states, thus causing a strong peak in the magnetoresistance near Tc. The non-monotonic angle dependence of the interlayer magnetoresistance is ascribed to the coexistence of the Josephson and two-dimensional Abrikosov vortices.

Interplay between the orbital quantization and Pauli effect in a charge-density-wave organic conductor £

Abstract The interlayer magnetoresistance of the low-dimensional organic metal α-(BEDT-TTF) 2 KHg(SCN) 4 under pressure shows features which are likely associated with theoretically predicted field-induced charge-density-wave (FICDW) transitions. At ambient pressure, a magnetic field strongly tilted towards the conducting layers induces a series of hysteretic anomalies. We attribute these anomalies to a novel kind of FICDW originating from a superposition of the orbital quantization of the nesting vector and Pauli effect on the charge-density wave.

Magnetoresistance of κ-(BEDT-TTF)2X in normal and mixed states

Abstract The interlayer magnetoresistance (MR) of κ-(BEDT-TTF)2X superconductors with X=Cu(NCS)2 and Cu[N(CN)2]Br in fields both above and below Hc2 has been studied. In the former salt, nearly temperature independent oscillations originating from the quantum interference in the magnetic breakdown regime have been directly observed above 2 K in fields 12–14 T. In contrast to the three-dimensional (3D) case, the effect survives at tilting the field from the crystallographic symmetry direction up to the angles as high as 40°. In the other salt clear MB oscillations corresponding to 100% of the Brillouin zone cross-section area have been found above 22 T. Below Hc2, the interlayer resistance is shown to be almost independent of the field direction in a wide angle range around the parallel-to-plane orientation. This result is believed to reflect the strongly two-dimensional nature of the vortex state in the title compounds.

The quantum Hall effect in organic metals with both quasi-two-dimensional and quasi-one-dimensional Fermi-surface components

The quantum Hall effect (QHE) is shown to be a natural property in high magnetic fields of any system possessing both quasi-two-dimensional and quasi-one-dimensional Fermi-surface components. Such Fermi surfaces are known to occur in some organic charge-transfer salts (e.g. with M=K, Tl, ). Whilst the QHE in two-dimensional semiconductor systems such as heterostructures and MOSFETs relies on the existence of localized states at the edges of the Landau levels, in organic metals the quasi-one-dimensional portion of the Fermi surface is shown to provide the necessary reservoir for pinning the chemical potential between the completely filled and empty Landau levels of the quasi-two-dimensional Fermi-surface section.