Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNon-Fermi-liquid behavior in quantum impurity models with superconducting channels
59
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We study how the non-Fermi-liquid nature of the overscreened multi-channel Kondo impurity model affects the response to a BCS pairing term that, in the absence of the impurity, opens a gap $Delta$. We find that non-Fermi liquid features do persist even at finite $Delta$: the local density of states lacks coherence peaks, the states in the continuum above the gap are unconventional, and the boundary entropy is a non-monotonic function of temperature. Even more surprisingly, we also find that the low-energy spectrum in the limit $Deltato 0$ actually does not correspond to the spectrum strictly at $Delta=0$. In particular, the $Deltato 0$ ground state is an orbitally degenerate spin-singlet, while it is an orbital singlet with a residual spin degeneracy at $Delta=0$. In addition, there are fractionalized spin-1/2 sub-gap excitations whose energy in units of $Delta$ tends towards a finite and universal value when $Deltato 0$; as if the universality of the anomalous power-law exponents that characterise the overscreened Kondo effect turned into universal energy ratios when the scale invariance is broken by $Delta ot=0$. This intriguing phenomenon can be explained by the renormalisation flow towards the overscreened fixed point and the gap cutting off the orthogonality catastrophe singularities.
rate research
Read More
Non-Fermi-liquid (NFL) behavior in the f-sublattice-diluted alloy system U_{1-x}Th_xPd_2Al_3 has been studied using ^{27}Al nuclear magnetic resonance (NMR). Impurity satellites due to specific U near-neighbor configurations to ^{27}Al sites are clearly resolved in both random and field-aligned powder samples. The spatial mean Kbar and rms spread delta K of impurity satellite shifts, which are related to the mean chibar and rms spread delta chi of the inhomogeneous susceptibility, have been measured in field-aligned powders with the crystalline c axis both perpendicular and parallel to the external field. The relatively narrow lines observed at low temperatures suggest that disorder- induced inhomogeneity of the f-ion--conduction-electron hybridization is not the cause of NFL behavior in these alloys: at low temperatures the experimental values of delta chi(T)/chibar(T) are much smaller than required by disorder- driven models. This is in contrast to results in at least some alloys with disordered non-f-ion nearest neighbors to f ions (ligand disorder), where disorder-driven theories give good accounts of NFL behavior. Our results suggest that f-ion dilution does not produce as much inhomogeneity of the hybridization strength as substitution on ligand sites.
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.
The phase diagram of BaVS3 is studied under pressure using resistivity measurements. The temperature of the metal to nonmagnetic Mott insulator transition decreases under pressure, and vanishes at the quantum critical point p_cr=20kbar. We find two kinds of anomalous conducting states. The high-pressure metallic phase is a non-Fermi liquid described by Delta rho = T^n where n=1.2-1.3 at 1K < T < 60K. At p<p_cr, the transition is preceded by a wide precursor region with critically increasing resistivity which we ascribe to the opening of a soft Coulomb gap.
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.
We study the temperature dependence of the electrical resistivity in a system composed of critical spin chains interacting with three dimensional conduction electrons and driven to criticality via an external magnetic field. The relevant experimental system is Yb$_2$Pt$_2$Pb, a metal where itinerant electrons coexist with localized moments of Yb-ions which can be described in terms of effective S = 1/2 spins with dominantly one-dimensional exchange interaction. The spin subsystem becomes critical in a relatively weak magnetic field, where it behaves like a Luttinger liquid. We theoretically examine a Kondo lattice with different effective space dimensionalities of the two interacting subsystems. We characterize the corresponding non-Fermi liquid behavior due to the spin criticality by calculating the electronic relaxation rate and the dc resistivity and establish its quasi linear temperature dependence.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
