1,721,091 research outputs found
Fermi surface fluctuations and single electron excitations near Pomeranchuk instability in two dimensions
No full textA metallic electron system near an orientational symmetry breaking
Pomeranchuk instability is characterized by a "soft" Fermi surface with
enhanced collective fluctuations. We analyze fluctuation effects in a
two-dimensional electron system on a square lattice in the vicinity of
a Pomeranchuk instability with d-wave symmetry, using a
phenomenological model which includes interactions with a small
momentum transfer only. We compute the dynamical density correlations
with a d-wave form factor for small momenta and frequencies, the
dynamical effective interaction due to a fluctuation exchange, and the
electron self-energy. At the quantum critical point the density
correlations and the dynamical forward scattering interaction diverge
with a dynamical exponent z=3. The singular forward scattering leads to
large self-energy corrections, which destroy Fermi liquid behavior over
the whole Fermi surface except near the Brillouin zone diagonal. The
decay rate of single-particle excitations, which is related to the
width of the peaks in the spectral function, exceeds the excitation
energy in the low-energy limit. The dispersion of maxima in the spectra
flattens strongly near those portions of the Fermi surface which are
remote from the zone diagonal. The contribution from classical
fluctuations to the self-energy spoils (omega/T) scaling in the quantum
critical regime
Fermi surface fluctuations and breakdown of Fermi liquid behavior
No full textElectron-electron interactions can induce Fermi surface deformations which break the point-group symmetry of the crystal structure of the system. In the vicinity of such a "Pomeranchuk instability" the Fermi surface is easily deformed by anisotropic perturbations, and exhibits enhanced collective fluctuations. We analyze Fermi surface fluctuation effects in a two-dimensional electron system on a square lattice in the vicinity of a Pomeranchuk instability with d-wave symmetry. At a quantum critical point d-wave density correlations and the dynamical forward scattering interaction diverge with a dynamical exponent z = 3. The singular forward scattering leads to large self-energy corrections, which destroy Fermi liquid behavior over the whole Fermi surface except near the Brillouin zone diagonal. The contribution from classical fluctuations to the self-energy spoils omega/T scaling in the quantum critical regime. We discuss to what extent d-wave Fermi surface fluctuations may play a role in cuprate superconductors
Non-Fermi Liquid Behavior from Critical Fermi Surface Fluctuations
No full textInteractions in Fermi systems can generate a Pomeranchuk instability leading to orientational symmetry breaking. that is. nematic order. In a metallic system close to such an instability the Fermi surface is easily deformed by anisotropic perturbations and exhibits enhanced collective fluctuations. We analyze fluctuation effects in the quantum critical regime near a d-wave Pomeranchuk instability in two dimensions. Density correlations with a d-wave form factor and the dynamical forward scattering interaction diverge near the instability. The singular forward scattering leads to large self-energy contributions, which destroy Fermi liquid behavior over the whole Fermi surface except at "cold spots" on the Brillouin zone diagonal. The decay rate of single-particle excitations, which is related to the width of the peaks in the spectral function. exceeds the excitation energy in the low-energy limit. The dispersion of the spectra flattens strongly near those portions of the Fermi surface which are remote from the zone diagonal. The decay rate for DC transport is linear in temperature except at the cold spots. We discuss the possible relevance of d-wave Fermi surface fluctuations for the "strange metal" behavior observed in the normal phase of cuprates
Electrical resistivity near Pomeranchuk instability in two dimensions
No full textWe analyze the dc charge transport in the quantum critical regime near a d-wave Pomeranchuk instability in two dimensions. The transport decay rate is linear in temperature everywhere on the Fermi surface except at cold spots on the Brillouin zone diagonal. For pure systems, this leads to a dc resistivity proportional to T3/2 in the low-temperature limit. In the presence of impurities the residual impurity resistance at T=0 is approached linearly at low temperatures
Nematic order and non-Fermi liquid behavior from a Pomeranchuk instability in a two-dimensional electron system
No full textInteractions in Fermi systems can induce a "Pomeranchuk instability" leading to orientational symmetry breaking, that is, nematic order. In a metallic system close to such an instability the Fermi surface is easily deformed by anisotropic perturbations, and exhibits enhanced collective fluctuations. We discuss electrons on a square lattice near a Pomeranchuk instability with d-wave symmetry. The strong response of such a system to a small orthorhombic perturbation can explain naturally the large in-plane anisotropy of electronic and magnetic properties observed in detwinned YBCO crystals. Fluctuations in a quantum critical regime near the instability provide a mechanism for non-Fermi liquid behavior. They lead to a singular forward scattering interaction, which destroys fermionic quasi-particles on the whole Fermi surface except at "cold spots" on the Brillouin zone diagonal
Scaling behavior of impurities in mesoscopic Luttinger liquids
No full textUsing a functional renormalization group, we compute the flow of the renormalized impurity potential for a single impurity in a Luttinger liquid over the entire energy range from the microscopic scale of a lattice-fermion model down to the low-energy limit. The nonperturbative method provides a complete real-space picture of the effective impurity potential. We confirm the universality of the open chain fixed point, but it turns out that very large systems (10(4) - 10(5) sites) are required to reach the fixed point for realistic choices of the impurity and interaction parameters
DMRG studies of impurities in Luttinger liquids
No full textUsing the Density Matrix Renormalization Group (DMRG) and various analytical techniques (functional renormalization) we consider the effects of local impurities in Luttinger liquids. We find that, the universal physics predicted by bosonization sets in only at extremely long, experimentally arguably irrelevant length scales or small energy scales respectively. The explicit construction of the RG flow allows to trace this behaviour to an extremely weak renormalization in real space of the impurities associated to the generation of a very long-ranged oscillating scattering potential
DMRG studies of impurities in Luttinger liquids
No full textUsing the Density Matrix Renormalization Group (DMRG) and various analytical techniques (functional renormalization) we consider the effects of local impurities in Luttinger liquids. We find that, the universal physics predicted by bosonization sets in only at extremely long, experimentally arguably irrelevant length scales or small energy scales respectively. The explicit construction of the RG flow allows to trace this behaviour to an extremely weak renormalization in real space of the impurities associated to the generation of a very long-ranged oscillating scattering potential
- …
