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C Rettori - One of the best experts on this subject based on the ideXlab platform.

  • Conduction Electrons in aperiodic versus periodic structures an esr study of quasicrystalline i y gd cd and its approximant y gd cd 6
    Physical Review B, 2019
    Co-Authors: M Cabrerabaez, M A Avila, C Rettori
    Abstract:

    A formal description of collective electronic states in condensed-matter systems lacking long-range periodicity remains a theoretical challenge. To experimentally explore the differences in electronic and magnetic behavior between metallic quasicrystals (QCs) and their conventional crystalline analogs [quasicrystal approximants (QCAs)], we have grown single crystals of ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}{\mathrm{Cd}}_{6}$ (QCA) together with their QC counterparts $i\text{\ensuremath{-}}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}\text{\ensuremath{-}}\mathrm{Cd}$ for $x=0.006$, 0.01, 0.1, and 1.00, and we carried out comparative $T$-dependent electron spin resonance (ESR) measurements. On the high Gd concentration side, $x=1.00$, we confirm that ${\mathrm{GdCd}}_{6}$ adopts an antiferromagnetic ground state below ${T}_{N}\ensuremath{\sim}22\phantom{\rule{4pt}{0ex}}\mathrm{K}$, whereas $i$-Gd-Cd presents spin-glass-like behavior showing similar local and dynamical properties from the point of view of ESR. For the diluted samples, our ESR experimental results show similar local Conduction electron polarization behavior at the ${\mathrm{Gd}}^{3+}$ site in all QC/QCA pairs investigated, supporting the validity of using QCAs as periodic representations of QCs in terms of short-range electronic interactions. However, there is a measurable difference in the Korringa relaxation rate (spin-flip relaxation process between the localized ${\mathrm{Gd}}^{3+}4f$ electron and the delocalized $s$-type Conduction Electrons at the Fermi surface) between the QC/QCA pairs probably associated with the lack of periodicity. We expect that our comparative ESR study may provide support and motivation for the development of new theoretical approaches toward a generalized band-structure theory, contemplating condensed-matter systems beyond the scope of traditional periodicity.

Yong Baek Kim - One of the best experts on this subject based on the ideXlab platform.

  • critical theory of non fermi liquid fixed point in multipolar kondo problem
    Physical Review X, 2020
    Co-Authors: Adarsh S Patri, Yong Baek Kim
    Abstract:

    A mathematical analysis reveals the existence of a novel type of non-Fermi liquid, an exotic metallic state governed by strong interactions between Conduction Electrons and a multipolar (ion) impurity.

  • critical theory of non fermi liquid fixed point in multipolar kondo problem
    arXiv: Strongly Correlated Electrons, 2020
    Co-Authors: Adarsh S Patri, Yong Baek Kim
    Abstract:

    When the ground state of a localized ion is a non-Kramers doublet, such localized ions may carry multipolar moments. For example, Pr$^{3+}$ ions in a cubic environment would possess quadrupolar and octupolar, but no magnetic dipole, moments. When such multipolar moments are placed in a metallic host, unusual interactions between these local moments and Conduction Electrons arise, in contrast to the familiar magnetic dipole interactions in the classic Kondo problem. In this work, we consider the interaction between a single quadrupolar-octupolar local moment and Conduction Electrons with $p$-orbital symmetry as a concrete model for the multipolar Kondo problem. We show that this model can be written most naturally in the spin-orbital entangled basis of Conduction Electrons. Using this basis, the perturbative renormalization group (RG) fixed points are readily identified. There are two kinds of fixed points, one for the two-channel Kondo and the other for a novel fixed point. We investigate the nature of the novel fixed point non-perturbatively using non-abelian bosonization, current algebra and conformal field theory approaches. It is shown that the novel fixed point leads to a, previously unidentified, non-Fermi liquid state with entangled spin and orbital degrees of freedom, which shows resistivity $\rho \sim T^{\Delta}$ and diverging specific heat coefficient $C/T \sim T^{-1 + 2\Delta}$ with $\Delta=1/5$. Our results open up the possibility of myriads of non-Fermi liquid states, depending on the choices of multipolar moments and Conduction electron orbitals, which would be relevant for many rare-earth metallic systems.

  • emergent non fermi liquid phenomena in multipolar quantum impurity systems
    Physical Review Research, 2020
    Co-Authors: Adarsh S Patri, Ilia Khait, Yong Baek Kim
    Abstract:

    In this work, the authors study the interactions between higher-rankmultipolar quantum impurities and Conduction Electrons in spin-orbitalentangled systems. Using perturbative renormalization grouptechniques, they uncover a number of novel non-Fermi liquid groundstates characterized by highly singular scaling behaviors in physicalproperties. The discovered non-Fermi liquid states are outside theknown categories of non-Fermi liquid states found in the conventionalmulti-channel Kondo problem

M Cabrerabaez - One of the best experts on this subject based on the ideXlab platform.

  • Conduction Electrons in aperiodic versus periodic structures an esr study of quasicrystalline i y gd cd and its approximant y gd cd 6
    Physical Review B, 2019
    Co-Authors: M Cabrerabaez, M A Avila, C Rettori
    Abstract:

    A formal description of collective electronic states in condensed-matter systems lacking long-range periodicity remains a theoretical challenge. To experimentally explore the differences in electronic and magnetic behavior between metallic quasicrystals (QCs) and their conventional crystalline analogs [quasicrystal approximants (QCAs)], we have grown single crystals of ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}{\mathrm{Cd}}_{6}$ (QCA) together with their QC counterparts $i\text{\ensuremath{-}}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}\text{\ensuremath{-}}\mathrm{Cd}$ for $x=0.006$, 0.01, 0.1, and 1.00, and we carried out comparative $T$-dependent electron spin resonance (ESR) measurements. On the high Gd concentration side, $x=1.00$, we confirm that ${\mathrm{GdCd}}_{6}$ adopts an antiferromagnetic ground state below ${T}_{N}\ensuremath{\sim}22\phantom{\rule{4pt}{0ex}}\mathrm{K}$, whereas $i$-Gd-Cd presents spin-glass-like behavior showing similar local and dynamical properties from the point of view of ESR. For the diluted samples, our ESR experimental results show similar local Conduction electron polarization behavior at the ${\mathrm{Gd}}^{3+}$ site in all QC/QCA pairs investigated, supporting the validity of using QCAs as periodic representations of QCs in terms of short-range electronic interactions. However, there is a measurable difference in the Korringa relaxation rate (spin-flip relaxation process between the localized ${\mathrm{Gd}}^{3+}4f$ electron and the delocalized $s$-type Conduction Electrons at the Fermi surface) between the QC/QCA pairs probably associated with the lack of periodicity. We expect that our comparative ESR study may provide support and motivation for the development of new theoretical approaches toward a generalized band-structure theory, contemplating condensed-matter systems beyond the scope of traditional periodicity.

C Pepin - One of the best experts on this subject based on the ideXlab platform.

  • violation of the wiedemann franz law at the kondo breakdown quantum critical point
    Physical Review Letters, 2009
    Co-Authors: C Pepin
    Abstract:

    : We study the electrical and thermal transport near the heavy-fermion quantum critical point, identified with the breakdown of the Kondo effect. We show that the electrical conductivity comes mainly from Conduction Electrons while the thermal conductivity is given by both Conduction Electrons and localized fermions (spinons), scattered with hybridization fluctuations of dynamical exponent z = 3. As a result, we reveal that not only electrical but also thermal resistivity displays quasilinear temperature dependence in the intermediate temperature range, the main prediction of our transport study. An important feature turns out to be emergence of additional entropy carriers, that is, spinon excitations. We find that the Wiedemann-Franz ratio should be larger than the standard value, differentiating the Kondo breakdown scenario from the Hertz-Moriya-Millis framework.

  • multiscale fluctuations near a kondo breakdown quantum critical point
    Physical Review B, 2008
    Co-Authors: I Paul, C Pepin, M Norman
    Abstract:

    We study the Kondo-Heisenberg model using a fermionic representation for the localized spins. The mean-field phase diagram exhibits a zero-temperature quantum critical point separating a spin liquid phase where the $f$-Conduction hybridization vanishes and a Kondo phase where it does not. Two solutions can be stabilized in the Kondo phase, namely, a uniform hybridization when the band masses of the Conduction Electrons and the $f$ spinons have the same sign and a modulated one when they have opposite sign. For the uniform case, we show that above a very small Fermi-liquid temperature scale, the critical fluctuations associated with the vanishing hybridization have dynamical exponent $z=3$, giving rise to a specific-heat coefficient that diverges logarithmically in temperature, as well as a Conduction-electron inverse lifetime that has a $T\text{ }\text{log}\text{ }T$ behavior. Because the $f$ spinons do not carry current, but act as an effective bath for the relaxation of the current carried by the Conduction Electrons, the latter result also gives rise to a $T\text{ }\text{log}\text{ }T$ behavior in the resistivity. This behavior is consistent with observations in a number of heavy fermion metals.

Adarsh S Patri - One of the best experts on this subject based on the ideXlab platform.

  • critical theory of non fermi liquid fixed point in multipolar kondo problem
    Physical Review X, 2020
    Co-Authors: Adarsh S Patri, Yong Baek Kim
    Abstract:

    A mathematical analysis reveals the existence of a novel type of non-Fermi liquid, an exotic metallic state governed by strong interactions between Conduction Electrons and a multipolar (ion) impurity.

  • critical theory of non fermi liquid fixed point in multipolar kondo problem
    arXiv: Strongly Correlated Electrons, 2020
    Co-Authors: Adarsh S Patri, Yong Baek Kim
    Abstract:

    When the ground state of a localized ion is a non-Kramers doublet, such localized ions may carry multipolar moments. For example, Pr$^{3+}$ ions in a cubic environment would possess quadrupolar and octupolar, but no magnetic dipole, moments. When such multipolar moments are placed in a metallic host, unusual interactions between these local moments and Conduction Electrons arise, in contrast to the familiar magnetic dipole interactions in the classic Kondo problem. In this work, we consider the interaction between a single quadrupolar-octupolar local moment and Conduction Electrons with $p$-orbital symmetry as a concrete model for the multipolar Kondo problem. We show that this model can be written most naturally in the spin-orbital entangled basis of Conduction Electrons. Using this basis, the perturbative renormalization group (RG) fixed points are readily identified. There are two kinds of fixed points, one for the two-channel Kondo and the other for a novel fixed point. We investigate the nature of the novel fixed point non-perturbatively using non-abelian bosonization, current algebra and conformal field theory approaches. It is shown that the novel fixed point leads to a, previously unidentified, non-Fermi liquid state with entangled spin and orbital degrees of freedom, which shows resistivity $\rho \sim T^{\Delta}$ and diverging specific heat coefficient $C/T \sim T^{-1 + 2\Delta}$ with $\Delta=1/5$. Our results open up the possibility of myriads of non-Fermi liquid states, depending on the choices of multipolar moments and Conduction electron orbitals, which would be relevant for many rare-earth metallic systems.

  • emergent non fermi liquid phenomena in multipolar quantum impurity systems
    Physical Review Research, 2020
    Co-Authors: Adarsh S Patri, Ilia Khait, Yong Baek Kim
    Abstract:

    In this work, the authors study the interactions between higher-rankmultipolar quantum impurities and Conduction Electrons in spin-orbitalentangled systems. Using perturbative renormalization grouptechniques, they uncover a number of novel non-Fermi liquid groundstates characterized by highly singular scaling behaviors in physicalproperties. The discovered non-Fermi liquid states are outside theknown categories of non-Fermi liquid states found in the conventionalmulti-channel Kondo problem