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We present results of comprehensive study of electronic properties of (TiZrNbCu)(1-x)Ni(x) metallic glasses performed in broad composition range x encompassing both, high entropy (HE) range, and conventional Ni-base alloy concentration range, x >= 0.35. The electronic structure studied by photoemission spectroscopy and low temperature specific heat (LTSH) reveal a split-band structure of density of states inside valence band with d-electrons of Ti, Zr, Nb and also Ni present at Fermi level N(E_F), whereas LTSH and magnetoresistivity results show that variation of N(E_F) with x changes in Ni-base regime. The variation of superconducting transition temperatures with x closely follows that of N(E_F). The electrical resistivities of all alloys are high and decrease with increasing temperature over most of explored temperature range, and their temperature dependence seems dominated by weak localization effects over a broad temperature range (10-300 K). The preliminary study of Hall effect shows positive Hall coefficient that decreases rapidly in Ni-base alloys., Comment: 32 pages, 6 figures

$\alpha$-(BEDT-TTF)$_2$I$_3$ is a prominent example of charge ordering among organic conductors. In this work we explore the details of transport within the charge-ordered as well as semimetallic phase at ambient pressure. In the high-temperature semimetallic phase, the mobilities and concentrations of both electrons and holes conspire in such a way to create an almost temperature-independent conductivity as well as a low Hall effect. We explain these phenomena as a consequence of a predominantly inter-pocket scattering which equalizes mobilities of the two types of charge carriers. At low temperatures, within the insulating charge-ordered phase two channels of conduction can be discerned: a temperature-dependent activation which follows the mean-field behavior, and a nearest-neighbor hopping contribution. Together with negative magnetoresistance, the latter relies on the presence of disorder. The charge-ordered phase also features a prominent dielectric peak which bears a similarity to relaxor ferroelectrics. Its dispersion is determined by free-electron screening and pushed by disorder well below the transition temperature. The source of this disorder can be found in the anion layers which randomly perturb BEDT-TTF molecules through hydrogen bonds., Comment: 10 pages, 7 figures, submitted to Physical Review B

Using a unique home-made cell for four-contact impedance spectroscopy of conductive liquid samples, we establish the existence of two low frequency conductivity relaxations in aqueous solutions of gelatin, in both liquid and gel state. A comparison with diffusion measurements using pulsed field gradient NMR shows that the faster relaxation process is due to gelatin macromolecule self-diffusion. This single molecule diffusion is mostly insensitive to the macroscopic state of the sample, implying that the gelation of gelatin is not a percolative phenomenon, but is caused by aggregation of triple helices into a system-spanning fibre network., Comment: 4 figures

We present an improved approach to the impedance spectroscopy of conductive liquid samples using four-electrode measurements. Our method enables impedance measurements of conductive liquids down to the sub-Hertz frequencies, avoiding the electrode polarization effects that usually cripple standard impedance analysers. We have successfully tested our apparatus with aqueous solutions of potassium chloride and gelatin. The first substance has shown flat spectra from $\sim$100 kHz down to sub-Hz range, while the results on gelatin clearly show the existence of two distinct low frequency conductive relaxations., Comment: 5 pages, 6 figures

We have measured the Hall effect on recently synthesized single crystals of quasi-one-dimensional organic conductor TTF-TCNQ, a well known charge transfer complex that has two kinds of conductive stacks: the donor (TTF) and the acceptor (TCNQ) chains. The measurements were performed in the temperature interval 30 K < T < 300 K and for several different magnetic field and current directions through the crystal. By applying the equivalent isotropic sample (EIS) approach, we have demonstrated the importance of the choice of optimal geometry for accurate Hall effect measurements. Our results show, contrary to past belief, that the Hall coefficient does not depend on the geometry of measurements and that the Hall coefficient value is around zero in high temperature region (T > 150 K), implying that there is no dominance of either TTF or TCNQ chain. At lower temperatures, our measurements clearly prove that all three phase transitions of TTF-TCNQ could be identified from Hall effect measurements., Comment: Revised version; 7 pages, 5 figures

Systematic study of electrical resistivity of Hf_{100-x}Fe_x (x=20,25), Hf_{100-x}Cu_x (x=30,40,50), and Ti_{65}Cu_{35} metallic glasses has been done in the temperature range 0.3 K - 290 K, and in magnetic fields B <= 5 T. All Hf-base alloys are superconducting with T_c >= 0.44 K, which is well above T_c of pure crystalline Hf (0.13 K). From the initial slopes of the upper critical fields, (dH_{c2}/dT)_{T_c}, and resistivities we determined the dressed electronic densities of states, N_{\gamma}(E_F), for all alloys. Both T_c and N_{\gamma}(E_F) decrease with increasing x (Fe and Cu content). The results are compared with those for corresponding Zr-base metallic glasses and ion-implanted Hf films., Comment: 9 pages, 4 figures, 1 table

At the (001) interface between the two band-insulators LaAlO3 and SrTiO3, a high-mobility electron gas may appear, which has been the object of numerous works over the last four years. Its origin is a subject of debate between the interface polarity and unintended doping. Here we use electron energy loss 'spectrum images', recorded in cross-section in a scanning transmission electron microscope, to analyse the Ti3+ ratio, characteristic of extra electrons. We find an interface concentration of Ti3+ that depends on growth conditions., Comment: 6 pages

Among known Bechgaard and Fabre salts (TMTSF)2NO3 is unique since it never becomes superconducting even under pressure. Also, though (TMTSF)2NO3 undergoes the spin density wave (SDW) transition, the low temperature transport is semimetallic and gapless. We propose: a) the absence of the superconductivity is due to the inverse symmetry breaking associated with the anion ordering at 45K; b) the SDW state below 9K should be unconventional as seen from the angle dependent magnetoresistance oscillation (AMRO); c) a new phase diagram for Bechgaard salts, where unconventional spin density wave (USDW) occupies the prominent space., Comment: AMN-3 Satellite Meeting, NBT-QT 2007, New Zealand

Among many Bechgaard salts, TMTSF2NO3 exhibits very anomalous low temperature properties. Unlike conventional spin density wave (SDW), TMTSF2NO3 undergoes the SDW transition at $\T_SDW\approx 9.5$ K and the low temperature quasiparticle excitations are gapless. Also, it is known that TMTSF2NO3 does not exhibit superconductivity even under pressure, while FISDW is found in TMTSF2NO3 only for P=8.5 kbar and B>20 T. Here we shall show that both the angle dependent magnetoresistance data and the nonlinear Hall resistance of TMTSF2NO3 at ambient pressure are interpreted satisfactory in terms of unconventional spin density wave (USDW). Based on these facts, we propose a new phase diagram for Bechgaards salts., Comment: 4 pages, 4 figs, RevTeX

We present the high-temperature (70 K < T < 300 K) resistivity anisotropy and Hall effect measurements of the quasi-one-dimensional (1D) organic conductor (TMTTF)2AsF6. The temperature variations of the resistivity are pronouncedly different for the three different directions, with metallic-like at high temperatures for the a-axis only. Above 220 K the Hall coefficient R_H is constant, positive and strongly enhanced over the expected value; and the corresponding carrier concentration is almost 100 times lower than calculated for one hole/unit cell. Our results give evidence for the existence of a high-temperature regime above 200 K where the 1D Luttinger liquid features appear in the transport properties. Our measurements also give strong evidence of charge ordering in (TMTTF)2AsF6. At the charge-ordering transition T_{CO} \approx 100 K, R_H(T) abruptly changes its behavior, switches sign and rapidly increases with further temperature decrease., Comment: RevTeX4, 8 pages, 6 figures

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 analyse 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., Comment: 5 pages, 6 figures

We investigated the transport properties of the quasi one-dimensional organic metal (TMTSF)2ReO4 above the anion-ordering metal-insulator transition (T_{AO} \approx 180K). The pronounced conductivity anisotropy, a small and smoothly temperature dependent Hall effect, and a small, positive and temperature dependent magnetoresistance are analyzed within the existing Fermi-liquid and non-Fermi liquid models. We propose that the transport properties of quasi one-dimensional Bechgaard salts at high temperatures can be described within the Fermi liquid description., Comment: RevTeX4, 8 pages, 5 figures, revised version

In spite of extensive experimental studies of the angular dependent magnetoresistance (ADMR) of the low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 about a decade ago, the nature of LTP remains elusive. Here we present a new study of ADMR of LTP in alpha-(ET)_2 salts assuming that LTP is unconventional charge density wave (UCDW). In the presence of magnetic field the quasiparticle 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 alpha-(BEDT-TTF)_2KHg(SCN)_4 remarkably well., Comment: 6 pages, 4 figures

Magnetoresistance in the spin-density wave (SDW) state of (TMTSF)2PF6 is known to exhibit a rich variety of the angular dependencies when a magnetic field B is rotated in the b'-c*, a-b' and a-c* planes. In the presence of a magnetic field the quasiparticle spectrum in the SDW with imperfect nesting is quantized. In such a case the minimum quasiparticle energy depends both on the magnetic field strength |B| and the angle \theta between the field and the crystal direction a, b' or c*. This approach describes rather satisfactory the magnetoresistance above T*~4K., Comment: 7 pages, 10 figures, EPL latex

The presence of subphases in spin-density wave (SDW) phase of (TMTSF)2PF6 below T* ~ 4K has been suggested by several experiments but the nature of the new phase is still controversial. We have investigated the temperature dependence of the angular dependence of the magnetoresistance in the SDW phase which shows different features for temperatures above and below T*. For T > 4K the magnetoresistance can be understood in terms of the Landau quantization of the quasiparticle spectrum in a magnetic field, where the imperfect nesting plays the crucial role. We propose that below T* ~ 4K the new unconventional SDW (USDW) appears modifying dramatically the quasiparticle spectrum. Unlike conventional SDW the order parameter of USDW depends on the quasiparticle momentum. The present model describes many features of the angular dependence of magnetoresistance reasonably well. Therefore, we may conclude that the subphase in (TMTSF)2PF6 below T* ~ 4K is described as SDW plus USDW., Comment: 7 pages, 9 figures, RevTeX4; misprint corrected, references updated, a few sentences added