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Register a new userNon-Fermi-liquid behavior and doping asymmetry in an organic Mott insulator interface
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High-$T_{rm C}$ superconductors show anomalous transport properties in their normal states, such as the bad-metal and pseudogap behaviors. To discuss their origins, it is important to speculate whether these behaviors are material-dependent or universal phenomena in the proximity of the Mott transition, by investigating similar but different material systems. An organic Mott transistor is suitable for this purpose owing to the adjacency between the two-dimensional Mott insulating and superconducting states, simple electronic properties, and high doping/bandwidth tunability in the same sample. Here we report the temperature dependence of the transport properties under electron and hole doping in an organic Mott electric-double-layer transistor. At high temperatures, the bad-metal behavior widely appears except at half filling regardless of the doping polarity. At lower temperatures, the pseudogap behavior is observed only under hole doping, while the Fermi-liquid-like behavior is observed under electron doping. The bad-metal behavior seems a universal high-energy scale phenomenon, while the pseudogap behavior is based on lower energy scale physics that can be influenced by details of the band structure.
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We report measurements of the bulk magnetic susceptibility and ^{29}Si nuclear magnetic resonance (NMR) linewidth in the heavy-fermion alloy CeRhRuSi_2. The linewidth increases rapidly with decreasing temperature and reaches large values at low temperatures, which strongly suggests the wide distributions of local susceptibilities chi_j obtained in disorder-driven theories of non-Fermi-liquid (NFL) behavior. The NMR linewidths agree well with distribution functions P(chi) which fit bulk susceptibility and specific heat data. The apparent return to Fermi-liquid behavior observed below 1 K is manifested in the vanishing of P(chi) as chi to infty, suggesting the absence of strong magnetic response at low energies. Our results indicate the need for an extension of some current theories of disorder-driven NFL behavior in order to incorporate this low-temperature crossover.
In this paper we study the low temperature behaviors of a system of Bose-Fermi mixtures at two dimensions. Within a self-consistent ladder diagram approximation, we show that at nonzero temperatures $Trightarrow0$ the fermions exhibit non-fermi liquid behavior. We propose that this is a general feature of Bose-Fermi mixtures at two dimensions. An experimental signature of this new state is proposed.
Muon spin rotation experiments on a stoichiometric sample of the non-Fermi liquid (NFL) heavy-fermion compound UCu_4Pd, in which recent neutron Bragg scattering measurements are consistent with an ordered structure, indicate that the U-ion susceptibility is strongly inhomogeneous at low temperatures. This suggests that residual disorder dominates NFL behavior. The data also indicate a short correlation length (lesssim 1 lattice spacing) for this inhomogeneity and a rapid low-temperature U-moment relaxation rate (gtrsim 10^{12} s^{-1}), which constrain cluster-based models of NFL behavior.
Triangular lattice quasi-two-dimensional Mott insulators based on BEDT-TTF molecule and its analogies present the largest group of spin liquid candidates on triangular lattice. It was shown theoretically that spin liquid state in these materials can arize from a coupling to the fluctuating charge degree of freedom. In this work we discuss magnetic properties of one of such materials, $kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl, which is known to be at the border of the phase transition from Mott insulator into a charge ordered state, and demonstrates charge order properties in the temperature range from 30 to 15~K. Our magnetic susceptibility and cantilever magnetisation measurements demonstrate an absence of spin order in this material down to 120~mK. We present arguments demonstrating that the charge order melting at low temperatures prevents ordering of spins.
We use midinfrared pulses with stable carrier-envelope phase offset to drive molecular vibrations in the charge transfer salt ET-F2TCNQ, a prototypical one-dimensional Mott insulator. We find that the Mott gap, which is probed resonantly with 10 fs laser pulses, oscillates with the pump field. This observation reveals that molecular excitations can coherently perturb the electronic on-site interactions (Hubbard U) by changing the local orbital wave function. The gap oscillates at twice the frequency of the vibrational mode, indicating that the molecular distortions couple quadratically to the local charge density.
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