Browsing by Author "Ingersent, Kevin"

Now showing 1 - 4 of 4
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    Kondo Destruction and Valence Fluctuations in an Anderson Model
    (American Physical Society, 2012) Pixley, J.H.; Kirchner, Stefan; Ingersent, Kevin; Si, Qimiao
    Unconventional quantum criticality in heavy-fermion systems has been extensively analyzed in terms of a critical destruction of the Kondo effect. Motivated by a recent demonstration of quantum criticality in a mixed-valent heavy-fermion system, -YbAlB4, we study a particle-hole-asymmetric Anderson impurity model with a pseudogapped density of states. We demonstrate Kondo destruction at a mixedvalent quantum critical point, where a collapsing Kondo energy scale is accompanied by a singular charge-fluctuation spectrum. Both spin and charge responses scale with energy over temperature (!=T) and magnetic field over temperature (H=T). Implications for unconventional quantum criticality in mixedvalence heavy fermions are discussed.
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    Pairing correlations near a Kondo-destruction quantum critical point
    (American Physical Society, 2015) Pixley, J.H.; Deng, Lili; Ingersent, Kevin; Si, Qimiao
    Motivated by the unconventional superconductivity observed in heavy-fermion metals, we investigate pairing susceptibilities near a continuous quantum phase transition of the Kondo-destruction type. We solve two-impurity Bose-Fermi Anderson models with Ising and Heisenberg forms of the interimpurity exchange interaction using continuous-time quantum Monte Carlo and numerical renormalization-group methods. Each model exhibits a Kondo-destruction quantum critical point separating Kondo-screened and local-moment phases. For antiferromagnetic interimpurity exchange interactions, singlet pairing is found to be enhanced in the vicinity of the transition. Implications of this result for heavy-fermion superconductivity are discussed.
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    Quantum criticality in the pseudogap Bose-Fermi Anderson and Kondo models: Interplay between fermion- and boson-induced Kondo destruction
    (American Physical Society, 2013) Pixley, J.H.; Kirchner, Stefan; Ingersent, Kevin; Si, Qimiao
    We address the phenomenon of critical Kondo destruction in pseudogap Bose-Fermi Anderson and Kondo quantum impurity models. These models describe a localized level coupled both to a fermionic bath having a density of states that vanishes like |ε|r at the Fermi energy (ε=0) and, via one component of the impurity spin, to a bosonic bath having a sub-Ohmic spectral density proportional to |ω|s. Each bath is capable by itself of suppressing the Kondo effect at a continuous quantum phase transition. We study the interplay between these two mechanisms for Kondo destruction using continuous-time quantum Monte Carlo for the pseudogap Bose-Fermi Anderson model with 0
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    Sequential localization of a complex electron fluid
    (National Academy of Sciences, 2019) Martelli, Valentina; Cai, Ang; Nica, Emilian M.; Taupin, Mathieu; Prokofiev, Andrey; Liu, Chia-Chuan; Lai, Hsin-Hua; Yu, Rong; Ingersent, Kevin; Küchler, Robert; Strydom, André M.; Geiger, Diana; Haenel, Jonathan; Larrea, Julio; Si, Qimiao; Paschen, Silke
    Complex and correlated quantum systems with promise for new functionality often involve entwined electronic degrees of freedom. In such materials, highly unusual properties emerge and could be the result of electron localization. Here, a cubic heavy fermion metal governed by spins and orbitals is chosen as a model system for this physics. Its properties are found to originate from surprisingly simple low-energy behavior, with 2 distinct localization transitions driven by a single degree of freedom at a time. This result is unexpected, but we are able to understand it by advancing the notion of sequential destruction of an SU(4) spin–orbital-coupled Kondo entanglement. Our results implicate electron localization as a unified framework for strongly correlated materials and suggest ways to exploit multiple degrees of freedom for quantum engineering.