Marginal Fermi Liquid Hypothesis Research Articles

Effect of vertex corrections on the charge and spin responses of the Fermi liquid

The effects of vertex corrections on the charge and spin responses of the Fermi liquid are considered. It is shown that the interaction in the particle - hole channel induces virtual pair excitations (Cooper pair like) in both the charge and the spin channels. It leads to the appearance of an anomalous Fermi-liquid term in both the charge and the spin responses of the Fermi liquid in addition to the normal response . Such a contribution of the anomalous term to the charge and spin responses is in agreement with the marginal Fermi-liquid hypothesis proposed by Varma et al to explain the universal anomalies in the normal state of cuprate high- superconductors.

Normal State Properties of High-Temperature Superconductors and the Marginal Fermi Liquid

The experimentally observed normal state thermodynamic and transport properties of cuprate superconductors are universally quite unusual and so far unexplained. Some of these will be reviewed and the challenges for an overall theoretical picture will be discussed. It will be described how, in some cases, the Marginal Fermi Liquid hypothesis may be applied.

Thermoelectric power of high-Tc superconductors: superconducting fluctuations and the marginal Fermi-liquid hypothesis

Some common trends observed in the temperature variation of the thermoelectric power (TEP) of high-Tc materials are theoretically analysed. In the first part of the analysis, we calculate the dominant effect of superconducting fluctuations on TEP, assuming that the conduction process occurs in two dimensions. In the second part of the analysis, we show that, by including the self-energy proposed in the marginal Fermi-liquid hypothesis along with that arising from superconducting fluctuations, one can understand the main features of the temperature variation of TEP. The magnitude of TEP given by the formula derived here is also of the right order.

Non-Fermi-liquid-like behaviors of the CuO 2 model of the high- Tc systems

We have studied the non-Fermi-liquid properties of the doped three-band CuO 2 model for the high- T c superconductors in the infinite U d slave-boson approach. The Green's functions of quasiparticles (d- and p-characters) as well as of the Cu d-electron for this model have been derived for the first time in the closed form by taking into account all the self-energies to order O(1/ N). We have examined the energy and temperature dependences of the imaginary parts of the self-energies and the spectral functions of Cu d- and oxygen p-electrons. It is found that charge fluctuations of quasiparticles due to constraint-field bosons give rise to the anomalous self-energy of quasiparticles which is consistent with experiment. Here the imaginary part of the d-electron self-energy exhibits a crossover from a quadratic (canonical Fermi liquid) to linear (non-canonical Fermi liquid) energy dependence above a small energy scale ω c≈0.01 eV for the hole doping (δ≈0.14), while the p-electron self-energy remains to be Fermi-liquid-like and does not contribute to the anomalous behavior. The origin of this characteristic energy scale ω c is discussed. The spectral functions of quasiparticles are asymmetric and are similar to the predictions of the marginal Fermi-liquid hypothesis.

Thermoelectric power studies on the BPSCCO system with silver addition

The effect of silver addition on the superconducting properties (resistance and thermoelectric power) of the Bi1.6Pb0.4Sr1.6Ca2Cu3Oy superconductor has been studied for silver concentrations of 0, 5, 10, 20 and 50 wt%. Silver is found to be nonreactive in so far as the onset Tc is found to remain unchanged at 110 K. Silver, however, diffuses through the grain boundaries of the rather low-density, 2223 material weakening the intergrain coupling. Tc0 (zero resistivity transition) is thus reduced with the addition of silver. The normal state thermoelectric power (TEP) of these specimens has been fitted to a formula derived from marginal Fermi liquid hypothesis. The normal state value of TEP decreases with increasing silver concentration. Ts0(zero TEP temperature) is almost the same for all these specimens and is higher than Tc0, confirming a lower percolation threshold for TEP than the percolation threshold for conductance.

Non-Fermi-liquid states of a magnetic ion in a metal.

A model of a local orbital coupled through repulsive interactions to both the hybridizing and the screening channels of a conduction band is solved by Wilson's renormalization group method. At particle-hole symmetry we find non-Fermi-liquid lines of critical points when the interaction in the screening channel is above a critical value. Away from particle-hole symmetry the system displays two stable Fermi-liquid fixed points of different symmetries, separated by a non-Fermi liquid quantum critical point, in the mixed-valence regime. The behavior in the vicinity of this point is consistent with the marginal Fermi-liquid hypothesis.

Temperature dependence of the X-ray photoemission line shape and of the hopping rate in a marginal Fermi liquid

The authors study the spectral properties of a localized particle (a deep core level, or a heavy particle hopping in a solid), coupled to conduction electrons that are described by a marginal Fermi liquid hypothesis. The main result is that, in this model, the core level line shape in an X-ray photoemission experiment shifts with temperature. The spectrum is consistent with the decrease of the hopping rate with decreasing temperature obtained by Zhang et al. (1992). In the presence of a distribution of energy levels for the hopping particle, the temperature dependence of the hopping rate is found to be less pronounced. The observability of both the shift in the X-ray photoemission spectrum and the decrease of the hopping rate depends on the strength of the interaction. A rough estimate of the value of the interaction parameter indicates that the effect might be observable in X-ray photoemission experiments.

Thermoelectric power of doped BSCCO superconductors and marginal Fermi liquid theory

Measurements of thermoelectric power of BSCCO superconductors doped with Sb and Li at various concentrations are reported. The authors also report a calculation of thermoelectric power based on the marginal Fermi liquid hypothesis. The calculation is valid above the transition temperature in the temperature range where the superconducting fluctuations play no significant role. The measured TEP data fit the derived formula rather well in the above temperature range (which in this case is 130 K to 300 K). Using the fits, the basic parameters-such as Fermi energy and those involved in the marginal Fermi liquid hypothesis-are derived.

The marginal Fermi liquid hypothesis and magnetic fluctuations in La 1.95Ba 0.05CuO 4

We report inelastic neutron scattering measurements on a single crystal of La 1.95Ba 0.05CuO 4. The magnetic correlation length does not change on warming to temperatures as high as 250 K. The magnetic response and its temperature dependence may be described by a temperature dependent local susceptibility of a form compatible with the marginal Fermi liquid hypothesis. In particular, we find a magnetic relaxation rate which varies as ħΓ ≈ 0.5 k B T for the metallic regime of our sample.

The de Haas-van Alphen effect in a marginal Fermi liquid

High field-low temperature modifications to the Lifshitz-Kosevich theory of the de Haas-van Alphen effect arise from the marginal Fermi-liquid hypothesis. Consequences of the hypothesis for de Haas-van Alphen frequencies and amplitudes are discussed.