Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session E37b: Exploring The Kondo Effect: Theory and Experiment |
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Sponsoring Units: DCMP GMAG Chair: Kefeng Wang, University of Maryland Room: 384 |
Tuesday, March 14, 2017 8:00AM - 8:12AM |
E37b.00001: Magnetic Field Tuned Crossover from Kondo effect to Fermi Liquid like Behavior in VTe$_{\mathrm{2}}$ single crystals Xiaxin Ding, Jie Xing, Gang Li, Luis Balicas, Hai-Hu Wen |
Tuesday, March 14, 2017 8:12AM - 8:24AM |
E37b.00002: Abstract Withdrawn We address the origin of the magnetic-field independent $-|A|\,T^{1/2}$ term observed in the low-temperature resistivity of several As-based metallic systems of the PbFCl structure type. For the layered compound ZrAs$_{1.58}$Se$_{0.39}$, we show that vacancies in the square nets of As give rise to the low-temperature transport anomaly over a wide temperature regime of almost two decades in temperature. This low-temperature behavior is in line with the non-magnetic version of the two-channel Kondo effect, whose origin we ascribe to a dynamic Jahn-Teller effect operating at the vacancy-carrying As layer with a $C_4$ symmetry. The pair-breaking nature of the dynamical defects in the square nets of As explains the low superconducting transition temperature $T_{\rm{c}}\approx 0.14$\,K of ZrAs$_{1.58}$Se$_{0.39}$, as compared to the free-of-vacancies homologue ZrP$_{1.54}$S$_{0.46}$ ($T_{\rm{c}}\approx 3.7$\,K). Our findings should be relevant to a wide class of metals with disordered pnictogen layers.\\ T. Cichorek et al, Phys.Rev. Lett. {\bf 117}, 106601 (2016) |
Tuesday, March 14, 2017 8:24AM - 8:36AM |
E37b.00003: Two-impurity Kondo physics in a mesoscopic device Lucas Peeters, Andrew Mitchell, Vladimir Umansky, David Goldhaber-Gordon When two quantum impurities are coupled both to each other and to a many-body electron reservoir, the outcome of the competition between inter-impurity (RKKY) and impurity-bath (Kondo) interactions can lead to a dramatic range of electronic behaviors. This two-impurity Kondo (2IK) problem is the basic building block of the Kondo lattice which is suspected to underlie much of the interesting but complex phenomenology seen in the heavy-fermion materials. We realize a mesoscopic model of this building block on a GaAs/AlGaAs heterostructure, allowing us to controllably vary the coupling between two quantum dots and their many-body baths, and explore the resulting conductance signature. [Preview Abstract] |
Tuesday, March 14, 2017 8:36AM - 8:48AM |
E37b.00004: The Effects of Kondo Physics on Surface State Mediated Exchange Interactions Andrew Allerdt, Adrian Feiguin We study the problem of two quantum spin-1/2 impurities on the (111) surface of a metal which hosts a Shockley surface state. Using a three orbital model for the bulk, the band structure is fitted to that of copper. We use an exact numerical method that combines a Lanczos transformation to map the band structure onto a one-dimensional chain, and the the density matrix renormalization group (DMRG) to solve the equivalent many-body problem. We find a non-trivial competiton between Kondo screening and indirect exchange coupling between the impurities, departing significantly from the standard 2D RKKY interaction. Effects of the bulk states are shown to play a crucial role by modifying the modulation of the RKKY interaction and enhancing screening effects. For comparison, a study of the triangular lattice is also presented. [Preview Abstract] |
Tuesday, March 14, 2017 8:48AM - 9:00AM |
E37b.00005: Kondo destruction and pairing enhancement in the single and two impurity SU(2) symmetric Bose-Fermi Anderson model Ang Cai, Qimiao Si Experiment on heavy fermion superconductor CeRhIn5 provides evidence of an underlying Kondo destruction quantum critical point (QCP) near the superconducting regime. Motivated by the experimental results, we studied the single impurity and two impurity SU(2) symmetric Bose-Fermi Anderson model with a vector bosonic bath, whose spectral function vanishes as a power-law. Using a recently developed continuous time quantum Monte Carlo algorithm [PRB 87 125102], in the single impurity problem we confirmed the epsilon expansion result [PRB 66 024426] of the existence of a critical phase and a Kondo destruction QCP. We further studied the two impurity model, coupled via an antiferromagnetic RKKY interaction, and a bosonic bath to the difference of their spin, both in an SU(2) symmetric way. We have identified the transition from the Kondo screened phase to an impurity singlet phase or a local moment phase. In both cases, the singlet pairing susceptibility is enhanced on the verge of Kondo destruction. Together with related work on the two impurity Anderson model with Ising anisotropy [PRB 91 201109 (R), arXiv:1604.06449], our results suggest pairing enhancement being a robust feature of Kondo destruction QCP, and also help elucidating the role of spin symmetry on the pairing tendency. [Preview Abstract] |
Tuesday, March 14, 2017 9:00AM - 9:12AM |
E37b.00006: Universality and scaling in a charge two-channel Kondo device Lars Fritz, Andrew Mitchell, Eran Sela, Aviad Landau We study a charge two-channel Kondo model, demonstrating that recent experiments [Iftikhar et al., Nature 526, 233 (2015)] realize an essentially perfect quantum simulation -- not just of its universal physics, but also nonuniversal effects away from the scaling limit. Numerical renormalization group calculations yield conductance lineshapes encoding RG flow to the critical point. By mimicking the experimental protocol, the experimental curve is reproduced quantitatively, although we show that far greater bandwidth/temperature separation is required to obtain the universal result. Fermi liquid instabilities are also studied: In particular, our exact analytic results for non-linear conductance provide predictions away from thermal equilibrium, in the regime of existing experiments. [Preview Abstract] |
Tuesday, March 14, 2017 9:12AM - 9:24AM |
E37b.00007: Resistivity crossover in the power-law Kondo systems Kazuto Noda, Tomonori Shirakawa, Seiji Yunoki We calculate temperature-dependent resistivity of Kondo systems with divergent structure of the density of states around the Fermi energy, which is given by $\rho(\omega)\propto|\omega|^{-p}$ $(0< p < 1)$, via Wilson's numerical renormalization group method. We clarify that these systems show specific resistivity crossover scaled with Kondo temperature $T_K$. Characteristic power-law divergence of resistivity in the Kondo region ($T\gg T_K$) leads to a novel dependence of the resistivity minimum. We also elucidate that the spectral density at the ground state shows peak structures around $\omega\simeq \pm T_K$ and a dip structure around the Fermi energy, whose structure reflects the resistivity crossover. Our findings might shed light on Kondo effects on a graphene. [Preview Abstract] |
Tuesday, March 14, 2017 9:24AM - 9:36AM |
E37b.00008: NRG study of field induced crossover from SU(4) to SU(2) Kondo state in a carbon nanotube quantum dot Yoshimichi Teratani, Akira Oguri, Rui Sakano, Meydi Ferrier, Tokuro Hata, Tomonori Arakawa, Kensuke Kobayashi We study Fermi-liquid properties of carbon nanotube quantum dot in the Kondo regime, using numerical renormalization group(NRG) method with a multi-orbital Anderson impurity model. Carbon nanotube quantum dot has orbital and spin degrees of freedom which give an variety to the Kondo effect. For instance, the SU(4) Kondo effect which is caused by the combination of these degrees of freedom has been observed[1]. Recently, a new type of crossover from SU(4) to SU(2) Kondo state evolving in magnetic field has been observed by transport measurements. This crossover can be explained by the fact that the two levels among four still remain near the Fermi level due to a matching between the orbital and spin Zeeman splitting. We have examined the low-energy Fermi-liquid behavior, which gradually varies as magnetic field increases[2]. The Fermi-liquid parameters such as renormalization factor continuously decrease from the SU(4) value to the SU(2) value. These results indicate that the electron correlation is significantly enhanced as symmetry lowers to the SU(2). \noindent [1] M.\ Ferrier,\ T.\ Arakawa,\ K.\ Kobayashi,\ {\it et al}, Nat. Phys. Lett. {\bf 12}, 230 (2016). \noindent [2] Y.\ Teratani, \ M.\ Ferrier, \ {\it et al}, J. Phys. Soc. Jpn. {\bf 85}, 094718 (2016) [Preview Abstract] |
Tuesday, March 14, 2017 9:36AM - 9:48AM |
E37b.00009: Bell pair creation in current of Kondo-correlated dot Rui Sakano, Akira Oguri, Yunori Nishikawa, Eisuke Abe Recently, local-Fermi-liquid properties in non-linear currents and shot noises through the Kondo dot have been investigated both theoretically and experimentally.\footnote{RS {\it et al}., Phys. Rev. Lett. {\bf 108}, 266401 (2012); M. Ferrier {\it et al}., Nat. Phys., Nature Physics {\bf 12}, 230–235 (2016).} We suggest a new entangled-electron-pair generator utilizing mechanism of quasiparticle-pair creation which has been observed as enhancement of shot noise in the quantum dot. Using the renormalized perturbation theory for an orbital-degenerate impurity Anderson model and the full counting statistics, we calculate the Clauser-Horne-Shimony-Holt type Bell’s correlator for currents \footnote{N. M. Chtchelkatchev {\it et al}., Phys. Rev. B {\bf 66}, 161320(R) (2002).} through correlated two different channels of a Kondo correlated dot. It is shown that residual exchange-interactions of the local-Fermi-liquid create spin-entangled quasiparticle-pairs in nonlinear current and this results in violation of the Bell’s inequality. [Preview Abstract] |
Tuesday, March 14, 2017 9:48AM - 10:00AM |
E37b.00010: Multi-pole orders and destruction of Kondo effect: Implications for quantum phase transitions in heavy-fermion systems Emilian Nica, Hsin-Hua Lai, Wen-Jun Hu, Shou-Shu Gong, Qimiao Si Motivated by the heavy-fermion systems [1] which exhibits multi-polar orders, we theoretically study an effective field theory of a Kondo lattice model involving both spin and quadrupole degrees of freedom. The field theory contains a quantum non-linear sigma model of the antiferroquadrupolar (AFQ) phase ordered at ($\pi$, $\pi$) in spin-1 systems [2], with Kondo couplings to three-flavors of conduction electrons in both the spin and quadrupolar sectors. In the absence of the Kondo coupling, we demonstrate the stability of the ($\pi$, $\pi$) AFQ phase using density renormalization renormalization group analysis in the underlying spin model. Considering the Kondo couplings, we use the renormalization group analysis [3] to show their exact marginality. Our results imply a destruction of Kondo effects in both the spin and quadrupolar channels in the AFQ phase, thereby suggesting a sequence of quantum phase transitions involving successive destructions of Kondo effects in the spin and quadrupolar channels. Implications of our results for the global phase diagram of heavy fermion systems are discussed. [1] J. Custers et al, Nat. Mater. 11, 189 (2012). [2] A. Smerald et. al., Phys. Rev. B 88, 184430 (2013). [3] Yamamoto S.J. and Q. Si, Phys. Rev. B 81, 205106 (2010). [Preview Abstract] |
Tuesday, March 14, 2017 10:00AM - 10:12AM |
E37b.00011: Filling Enforced Semimetals and Fractionalized Phases in Nonsymmorphic Kondo Lattices Brett Brandom, J.H. Pixley, Sungbin Lee, S.A. Parameswaran The competition between frustrated magnetic exchange interactions and Kondo screening in heavy-fermion systems can lead to phase transitions that involve a change in the volume of the Fermi surface. Remarkably, such transitions can be continuous and are consistent with Luttinger’s theorem as long as the local moments are included in the Luttinger count. In such a scenario, in the screened phase, local moments and conduction electrons combine into a ‘large’ Fermi sea of heavy electrons. When exchange dominates screening, but magnetic order is frustrated, this can give way to a fractionalized Fermi liquid: local moments form a spin liquid described at low energies by a deconfined gauge theory with exotic, fractionalized excitations, while the conduction electrons fill a ‘small’ Fermi sea. We complement this picture by applying a recent extension of Luttinger’s theorem that incorporates crystal symmetries, and show that the presence of nonsymmorphic symmetries enriches the small-large Fermi surface transition in a manner that cannot be gleaned from Luttinger’s theorem alone. In particular we discuss filling-enforced semimetallic behavior on either side of the transition and how nonsymmorphic symmetries stabilize these phases from opening up a gap. [Preview Abstract] |
Tuesday, March 14, 2017 10:12AM - 10:24AM |
E37b.00012: Realistic model of cubic hastatic order John Van Dyke, Guanghua Zhang, Rebecca Flint We study the role of Kondo physics in cubic materials with non-Kramers doublet grounds states, motivated by PrV2Al20 and other compounds. These systems generically display a two-channel Kondo effect, involving valence fluctuations between the non-Kramers doublet ground state and an excited Kramers doublet. In contrast to the single channel case, here the formation of a heavy Fermi liquid or Kondo insulator requires a channel symmetry-breaking phase transition, known as hastatic order. Introducing a simple but realistic two-channel Anderson lattice model, we explore the experimental consequences of hastatic order. These include a necessary breaking of time-reversal symmetry as indicated by the development of a conduction electron magnetic moment. [Preview Abstract] |
Tuesday, March 14, 2017 10:24AM - 10:36AM |
E37b.00013: Skyrmion defects of antiferromagnet and its competing singlet states in a Kondo-Heisenberg model Chia-Chuan Liu, Pallab Goswami, Qimiao Si The competition between antiferromagnetism and a variety of proximate paramagnetic spin-singlet states is a common feature for many heavy fermion compounds, and has been discussed in the proposed global phase diagram [1]. It is important yet a challenging problem to develop a general scheme to access the paramagnetic, spin singlet states from the antiferromagnetically ordered side, and vice versa. In this work, we study the problem on a honeycomb lattice by starting from the Kondo-destroyed antiferromagnetic phase. Here, the local moment is represented by a non-linear sigma model field, whose topological defects are known to induce the singlet orders based on a perturbative gradient expansion [2]. By solving low energy effective Dirac Hamiltonian in the skyrmion background, we identify the singlet orders through an enhanced correlations in the corresponding channels. In the Kondo lattice model, we find two leading singlet channels, one in the spin Peierls and the other in the Kondo singlet. The relative stability of the Kondo singlet and spin Peierls channels is tuned by varying the Kondo coupling. Our results provide new insight into the global phase diagram of the heavy fermion systems. \textbf{References:} [1] Q. Si, Phys. Status Solidi 247, 476 (2010); Physica B 378, 23 (2006). [2] P. Goswami and Q. Si, Phys. Rev. B \textbf{89}, 045124 (2014). [Preview Abstract] |
Tuesday, March 14, 2017 10:36AM - 10:48AM |
E37b.00014: Variational Cluster Approach to Superconductivity and Magnetism in the Kondo Lattice Model Benjamin Lenz, Riccardo Gezzi, Salvatore R. Manmana We present results for the interplay of d-wave superconductivity and antiferromagnetism in the Kondo lattice model using the variational cluster approximation (VCA). Both the paramagnetic and the antiferromagnetic phase of the model are investigated and regions with different Fermi surface topology are found in the latter. VCA is used to probe the system for s-wave and d-wave superconductivity for all coupling regions. It is shown that only by treating antiferromagnetism and superconductivity on equal footing artificial superconducting solutions at half-filling can be avoided. No true s-wave superconducting solutions due to correlation effects are found, but d-wave pairing proved to be robust for various coupling strengths off half-filling. Its interplay with antiferromagnetism is analyzed at weak coupling. [Preview Abstract] |
Tuesday, March 14, 2017 10:48AM - 11:00AM |
E37b.00015: Visualizing the impact of valence fluctuation in the momentum space in a mixed valence system Shouvik Chatterjee, Jacob Ruf, Haofei Wei, Kenneth Finkelstein, Darrell Schlom, Kyle Shen In mixed valence systems, impact of valence fluctuation on the low-energy band structure and Fermi surface topology is of fundamental importance to gain understanding of their emergent properties and inherent k-space susceptibilities, but has remained enigmatic due to a lack of appropriate experimental probes. Here, we employ molecular-beam epitaxy (MBE) to synthesize epitaxial thin films of the prototypical mixed valence system YbAl3 and utilize in situ high-resolution angle-resolved photoemission spectroscopy (ARPES) to directly visualize the evolution of its low-energy band structure while tracking the change in Yb valence as temperature is varied. Our measurements reveal a dramatic temperature dependent shift in chemical potential leading to a Lifshitz transition of a small electron Fermi surface that exactly matches the change in Yb valence determined from core level spectroscopy without any scaling factor. I will describe a unified picture of how local valence fluctuations connect to momentum-space concepts such as band filling and Fermi surface topology in the classic problem of mixed valence systems. [Preview Abstract] |
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