Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session B10: Non-Fermi Liquids |
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Sponsoring Units: DMP Chair: Anton Burkov, Harvard University Room: Colorado Convention Center Korbel 1E |
Monday, March 5, 2007 11:15AM - 11:27AM |
B10.00001: Nonanalytic Magnetic Response of Fermi- and non-Fermi Liquids Andrey Chubukov, Dmitrii Maslov, Ronojoy Saha We revisit the issue of the non-analytic dependence of the static spin susceptibility of a 2D Fermi liquid on temperature and a magnetic field, $\chi_s (T, H) = \chi_0 + A T f_\chi (\mu_B |H|/T)$. We show that in a generic Fermi liquid the prefactor $A$ is expressed via complex combinations of the Landau parameters, and does not reduce to the backscattering amplitude, contrary to the case of the specific heat $C(T, H)$. We show that this distinction with the specific heat is mostly relevant near a ferromagnetic QCP -- the non-analytic terms in $\chi_s (T,H) $ are less singular near QCP than those in $C(T, H)$. [Preview Abstract] |
Monday, March 5, 2007 11:27AM - 11:39AM |
B10.00002: Derivation of the Marginal Fermi Liquid for the Cuprates Vivek Aji, Chandra Varma The statistical mechanics of the time-reversal and inversion symmetry breaking order parameter, possibly observed in the pseudogap region of the phase diagram of the Cuprates,can be represented by the Ashkin-Teller model. We add kinetic energy and dissipation to the model for a quantum generalization and show that the correlations are determined by two sets of charges, one interacting locally in time and logarithmically in space and the other locally in space and logarithmically in time. The quantum critical fluctuations are derived and shown to be of the form postulated in 1989 to give the marginal fermi-liquid properties. The model solved and the methods devised are likely to be of interest also to other quantum phase transitions. [Preview Abstract] |
Monday, March 5, 2007 11:39AM - 11:51AM |
B10.00003: Pomeranchuk instabilities of Fermi fluids in the spin channel Kai Sun, Congjun Wu, Eduardo Fradkin, Shou-Cheng Zhang We study the Pomeranchuk instabilities of the Fermi surface in the spin channel. It is shown that the instabilities will lead to two classes of the ordered phases, the $\alpha$ and $\beta$-phases, named by analogy to the superfluid $^3$He-A and B-phases. The Fermi surfaces in the $\alpha$-phases exhibit spontaneous anisotropic distortions, while those in the $\beta$-phases remain circular with non-trivial spin configurations in momentum space. The low energy excitations of the ordered phases are studied by RPA approximation. In the $\alpha$-phases, the density excitations exhibit anisotropic overdamping and the spin density excitations are nearly isotropic and underdamped at small propagating wavevectors. The $\beta$-phases shows a Lifshitz- like instability in the $p$-wave channel, and will stabilize a chiral ground state inhomogeneity. [Preview Abstract] |
Monday, March 5, 2007 11:51AM - 12:03PM |
B10.00004: Theory of non-fermi liquid in a diagonal electronic nematic state Hae Young Kee, Ying-Jer Kao We study the fluctuation effects of the diagonal electronic nematic order on a two dimensional square lattice. It has been shown that there exists a quantum critical point between the diagonal nematic and isotropic phases.[1] We study the correlations near the critical point, where the singular forward scattering leads to a non-Fermi liquid behavior over the whole Fermi surface except along the (0,$\pi$) and ($\pi$,0) directions. We will also discuss the decay rate of the single-particle excitations as functions of temperature and chemical potential. \newline \newline [1] Hyeonjin Doh, Nir Friedman, Hae-Young Kee, Phys. Rev. B 73, 125117 (2006) [Preview Abstract] |
Monday, March 5, 2007 12:03PM - 12:15PM |
B10.00005: Diamagnetism of nodal fermions in semimetals: graphene and significant others Amit Ghosal, Pallab Goswami, Sudip Chakravarty Nodal fermionic excitations are interesting examples of the simplest fermionic quantum criticality in which the dynamic critical exponent $z=1$, and the quasiparticles are well defined. They arise in a number of physical contexts. We derive the scaling form of the diamagnetic susceptibility, $\chi$, at finite temperatures, $T$, and finite chemical potential, $\mu$. From measurements in graphene, or in $Bi_{1-x}Sb_{x}$ ($x=0.4$), one may be able to infer the striking quantum critical Landau diamagnetic susceptibility of the system at $T=0$ and $\mu=0$, $\chi\propto - H^{-1/2 }, \; H\to 0$, where $H$ is the magnetic field. Although the quasiparticles in the mean field description of the proposed $d$-density wave (DDW) condensate in a high temperature superconductors is another example of nodal quasiparticles, the crossover from the high temperature behavior, $\chi\propto - T^ {-1} $, and the quantum critical behavior takes place at a far lower temperature due to the reduction of the velocity scale from the fermi velocity $v_{F}$ in graphene to $\sqrt{v_{F}v_{DDW}}$, where $v_{DDW}$ is the velocity in the direction orthogonal to the nodal direction at the Fermi point of the spectra of the DDW condensate. [Preview Abstract] |
Monday, March 5, 2007 12:15PM - 12:27PM |
B10.00006: Self-energy corrections to anisotropic Fermi surfaces Rafael Roldan, M. Pilar Lopez-Sancho, Francisco Guinea, Shan-Wen Tsai The electron-electron interactions affect the low-energy excitations of an electronic system and induce deformations of the Fermi surface. These effects are especially important in anisotropic materials with strong correlations, such as copper oxides superconductors or ruthenates. In this talk I will analyze the deformations produced by electronic correlations in the Fermi surface of anisotropic two-dimensional systems, treating the regular and singular regions of the Fermi surface on the same footing. Simple analytical expressions are obtained for the corrections, based on local features of the Fermi surface, as the Fermi velocity and curvature. It will be shown that, even for weak local interactions, the behavior of the self-energy is non trivial, showing a momentum dependence and a self-consistent interplay with the Fermi surface topology. Applications of the method to cuprates- and Sr$_{2}$RuO$_{4}$-like Fermi surfaces will be shown. R. Roldan, M.P. Lopez-Sancho, F. Guinea and S.-W. Tsai; cond-mat/0603673 [Preview Abstract] |
Monday, March 5, 2007 12:27PM - 12:39PM |
B10.00007: Gradient Expansion approach to interacting Fermi Liquids Ryuichi Shindou, Leon Balents Starting from the Keldysh equation for a general multiple band Fermi liquid (FL), we project out fully occupied / empty bands and derive the SU(2) reduced Keldysh equation (RKE), only to discuss the low-energy property of those quasi-particles which are constrained within a single Fermi surface. The RKE thus derived characterizes quasi-particle dynamics in terms of Berry's curvatures defined in the (d+1) dual space. Namely, in addition to the well-studied ``k-space magnetic field'', our Fermi liquid formulations naturally introduce ``k-space electric field'', as the Berry's curvature in frequency and momentum space. When solving the derived RKE in favor of spectral functions, we observed that these artificial electromagnetic fields enter into the linear response of the spectral weight against real applied electromagnetic fields. This theoretical observation naturally lets us raise several photoemission experiments as the candidate experimental tool to measure both U(1) and SU(2) artificial fields in a momentum resolved way, which is widely demanded from the (spin) galvanomagnetic community. Restricting ourselves to the U(1) FLs, we further derive the U(1) Boltzmann equation out of this RKE, to find that not only the artificial magnetic field but also the electric fields enters into the effective EOM for quasi-particles as the Lorentz force in k-space. [Preview Abstract] |
Monday, March 5, 2007 12:39PM - 12:51PM |
B10.00008: Effect of Nonmagnetic Impurity in Nearly Antiferromagnetic Fermi Liquid: Magnetic Correlations and Transport Phenomena Hiroshi Kontani, Masanori Ohno In nearly AF metals such as high-Tc superconductors (HTSCs), heavy fermion systems and organic superconductors, a single nonmagnetic impurity frequently causes nontrivial widespread change of the electronic states. To elucidate this long-standing issue, we study a Hubbard model with a strong onsite impurity potential based on an improved fluctuation-exchange (FLEX) approximation, which we call the $GV^I$-FLEX method. We find that (i) both local and staggered susceptibilities are strongly enhanced around the impurity. By this reason, (ii) the quasiparticle lifetime as well as the local DOS are strongly suppressed in a wide area around the impurity (like a Swiss cheese hole), which causes the ``huge residual resistivity'' beyond the s-wave unitary scattering limit. We stress that the excess quasiparticle damping rate caused by impurities has strong momentum-dependence due to non-s-wave scatterings induced by many-body effects, so the structure of the ``hot spot/cold spot'' in the host system persists against impurity doping. This result could be examined by the ARPES measurements. In addition, (iii) only a few percent of impurities can causes a ``Kondo-like'' upturn of resistivity ($d\rho/dT<0$) at low temperatures when the system is very close to the AF quantum critical point (QCP). We also discuss the impurity effect in the superconducting state. [Preview Abstract] |
Monday, March 5, 2007 12:51PM - 1:03PM |
B10.00009: Kondo physics in a dissipative environment K. Ingersent, M. T. Glossop, N. Khoshkhou In recent years impurity models with quantum critical points have attracted much interest. Well-studied examples include the pseudogap and Bose-Fermi Kondo models. In the former model, the depletion of the host density of states at the Fermi level can destroy the Kondo effect; in the latter case, Kondo screening competes with coupling to a dissipative bosonic bath representing, e.g., collective spin fluctuations of the host. The physics of both models is dominated by an interacting quantum critical point. Here, we focus on the more general case of a magnetic impurity interacting with a pseudogap fermionic density of states $\rho(\epsilon)\propto |\epsilon|^r$ and with a bosonic bath having a spectral function $B(\omega)\propto \omega^s$. Perturbative renormalization-group (RG) studies of the resulting model, discussed in relation to Kondo temperature suppression in underdoped cuprates [1], have established a rich phase diagram with three stable and two critical fixed points. We report nonperturbative results for this model, obtained using a Bose-Fermi numerical RG approach [2]. We discuss the phase diagram for the Ising-anisotropic case, together with quantum critical properties probed via response to a local magnetic field. [1] M.\ Vojta and M.\ Kir\'{c}an, PRL {\bf 90}, 157203 (2003). [2] M.\ T.\ Glossop and K.\ Ingersent, PRL {\bf 95}, 067202 (2005); PRB (2006). [Preview Abstract] |
Monday, March 5, 2007 1:03PM - 1:15PM |
B10.00010: Nonequilibrium steady-state density of states for a strongly correlated electron system in the presence of a large electric field. Alexander Joura, Jim Freericks The electronic density of states (DOS) of the Falicov-Kimball model in a constant uniform electric field $E$ is calculated using a Kadanoff-Baym-Keldysh nonequilibrium Green's function technique and dynamical mean-field theory. When the electron-electron interaction $U$ vanishes, the DOS is the Wannier-Stark ladder of delta functions spaced by the Bloch frequency. If $U$ is increased, the delta function peaks initially broaden due to the scattering, but ultimately evolve into a continuous structure for large $U$'s. As $E$ is increased from small values, where linear response theory can be used and we see broadened Wannier-Stark peaks, the DOS develops a shape with large peaks at miniband edges, separated in energy by $U$. We verify the accuracy of our calculations by checking the DOS against frequency-moment sum rules, and an independent transient-response calculation of the Green's functions at long times. While our formalism has been applied to the Falicov-Kimball model, it can also be directly extended to other models like the Hubbard or periodic Anderson model, by using more complicated impurity problem solvers. [Preview Abstract] |
Monday, March 5, 2007 1:15PM - 1:27PM |
B10.00011: Experimental Evidence of Spin-Incoherent Luttinger Liquid State in Semiconductor Quantum wires Mustafa Muhammad, Steven Herbert, Richard Newrock, Philippe Debray We have measured the Coulomb drag between two spatially separated parallel quantum wires in the absence of tunneling to experimentally probe the recently proposed spin-incoherent Luttinger liquid (SILL) state. This new state is considered to exist in one-dimensional electron systems when the electron density is sufficiently low and the electron-electron interaction is strong, leading to \textit{J$<<$T$<<$E}$_{F}$, where $J $is the exchange coupling of spins and $E_{F}$ the Fermi energy. The measured drag resistance in the strictly one-dimensional (1D) transport regime is found to follow a power-law temperature dependence with a negative exponent (-0.65) in the temperature range 70mK -- 1.2K, in excellent agreement with the prediction of SILL theory for 4k$_{F}$ backscattering. The drag resistance is also found to decay exponentially with wire separation confirming the backscattering nature of the momentum transfer process. [Preview Abstract] |
Monday, March 5, 2007 1:27PM - 1:39PM |
B10.00012: Hall effect in strongly correlated low dimensional systems Gladys Leon, Christophe Berthod, Thierry Giamarchi We investigate the Hall effect in a quasi one-dimensional system made of weakly coupled Luttinger liquids at half filling. A memory function approach is used to compute the Hall resistivity ($R_H$) in the presence of umklapp scattering along the chains. In this approximation, the Hall resistivity decomposes into two terms linear in the magnetic field: an infinite frequency limit term and a memory function term. We investigate the case of zero umklapp scattering, where the memory function vanishes and the Hall resistivity is given by a simple formula corresponding to non-interacting fermions, in agreement with former results made on weakly coupled Luttinger Liquids in the absence of dissipation along the chains. With umklapp scattering present, we find a negative power-law correction to the free-fermion value (band value), with an exponent depending on the Luttinger parameter $K_{\rho}$. We also calculate $R_H$ for the case of noninteracting fermions with umklapp scattering present using Feymnan diagrams to compare with the limit $K_{\rho} \to 1$ of the power-law result. At high enough temperature or frequency, the Hall coefficient approaches the band value $R_H^0$. cond-mat/0608427 [Preview Abstract] |
Monday, March 5, 2007 1:39PM - 1:51PM |
B10.00013: ABSTRACT WITHDRAWN |
Monday, March 5, 2007 1:51PM - 2:03PM |
B10.00014: ABSTRACT WITHDRAWN |
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