Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C07: Heavy Fermion and Correlated Electron Metals |
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Sponsoring Units: DCMP Chair: James Hamlin, University of Florida Room: BCEC 109B |
Monday, March 4, 2019 2:30PM - 2:42PM |
C07.00001: Spin-orbit interaction and quasiparticle bands in locally non-centrosymmetric heavy-fermion systems Gertrud Zwicknagl, Seunghyun Khim, Manuel Brando, Christoph Geibel Non-centrosymmetric heavy-fermion systems (HFS) have gained much interest in the past decade. In these materials, the lack of inversion symmetry in combination with strong spin-orbit interaction and magnetic interactions can lead to novel phenomena. In this talk, we present calculations of the heavy quasiparticle bands in Ce- and Yb-based HFS from the tetragonal 122-family. This class of materials comprises compounds with the inversion-symmetric ThCr2Si2 structure as well as systems with the locally non-centrosymmetric CaBe2Ge2 structure. The calculations are performed by means of the Renormalized Band method which proceeds from a Dirac.relativistic description of the electronic structure and accounts for Crystalline Electric Field effects and the mass renormalization due to strong local correlations. We discuss results for YbIr2Si2 which crystallizes in both structures depending on preparation condition. Further on, we present results on the new HFS CeRh2As2. |
Monday, March 4, 2019 2:42PM - 2:54PM |
C07.00002: The high-field/high-pressure relationship of magnetic order and nematicity in the heavy fermion superconductor CeRhIn5 Toni Helm, Audrey Grockowiak, Fedor Balakirev, John Singleton, Kent Shirer, Markus Koenig, Eric Bauer, Filip Ronning, Stanley W Tozer, Philip Moll Recently, a nematic signature, i.e. a sudden resistivity anisotropy above a critical field B* = 28 T, has been observed in CeRhIn5[1]. This heavy fermion antiferromagnet (TN = 3.85 K) superconducts under pressure above pc = 23 kbar, associated with an antiferromagnetic quantum critical point (QCP). The reported nematic behavior survives at ambient pressure only until magnetic order is suppressed at a critical field of Bc =51 T, associated with a second QCP[2,3]. An open question is if and how the two QCPs, B-induced nematicity and p-induced superconductivity (SC) are related. |
Monday, March 4, 2019 2:54PM - 3:06PM |
C07.00003: Quantum confinement of electronic states in a bulk heavy fermion crystal Nicolas Gauthier, Jonathan Sobota, Makoto Hashimoto, Zhixun Shen Electronic states become quantized when confined in a potential well. This well-known phenomenon is observed for example in quantum dots or thin films [1]. In these cases, the confinement is created artificially by the microscopic dimensions of the system. Surprisingly, we recently observed the presence of confined electronic states in a bulk crystal of CeCoIn5, a prototypical heavy fermion superconductor [2]. Our recent ARPES results revealed multiple electronic bands that were not observed previously [3-5] and are not predicted by theory [6]. Interestingly, the energy position of these bands follows the simple relation expected for a quantum well. In comparison to thin films, the origin of the confinement potential creating these quantized states in CeCoIn5 is still unclear and requires more investigations. |
Monday, March 4, 2019 3:06PM - 3:18PM |
C07.00004: Structural and Physical Properties of CeAu2Bi: a New Frustrated Antiferromagnet Candidate Mario Moda Piva, Filip Ronning, Joe D Thompson, Pascoal Pagliuso, Priscila Rosa Ce-based compounds often display emergent phenomena due to the interplay between competing magnetic interactions, crystalline electrical field (CEF) effects, and the Kondo effect. Here we report the structural and physical properties of the new heavy-fermion compound CeAu2Bi. CeAu2Bi crystallizes in a hexagonal structure (P63/mmc) with lattice parameters of a = 4.8867(5) Å and c = 9.3748(13) Å. This structure presents Ce planes containing a triangular lattice, which has the potential of displaying geometrical frustration. Antiferromagnetic ordering, however, takes place at TN = 3.1 K, and is enhanced as a function of pressure, reaching 4.2 K at 18 kbar. We discuss our experimental results in the light of band structure calculations. |
Monday, March 4, 2019 3:18PM - 3:30PM |
C07.00005: Theory of multipolar order and unconventional superconductivity
in heavy fermion systems; importance of nonlocal vertex corrections Rina Tazai, Hiroshi Kontani In heavy-fermion systems, higher-rank multipole operators are active thanks to the strong spin-orbit interaction (SOI). Therefore, multipole fluctuations cause rich quantum critical phenomena, such as unconventional superconductivity and hidden-order phase. However, the microscopic pictures of these phenomena have not been fully understood. To solve these issues, we study higher-rank multipole fluctuations by considering the vertex corrections (VCs), which represent higher-order many body effects, on the basis of multi-orbital Periodic Anderson Model [1]. We find that the significant effects are given by Aslamazov-Larkin process, which originate from strong interference between multipole fluctuations. Due to the AL-VC, various types of multipole fluctuations develop simultaneously near the magnetic QCP. Especially, some electric multipole (quadrupole or hexadecapole) fluctuations are drastically enlarged, which remain small in mean field theories. Thus, various interesting phase due to the electric multipole fluctuations are expected to be realized in heavy fermion systems. In this talk, we discuss both the s-wave superconductivity in CeCu2Si2 [1] and the hidden-order phase in CeB6, which are reported by recent improved experiments. [1] R. tazai and H. kontani, arXiv:1807.11427. |
Monday, March 4, 2019 3:30PM - 3:42PM |
C07.00006: Magnon Bose-Einstein Condensation in a Heavy Fermion Metal Snir Gazit, Pavel Volkov, Jed Pixley Recent experiments on heavy fermion materials have revealed a range of compounds that are both metallic and have local magnetic moments that reside on geometrically frustrated lattices. An interesting example of frustration, realized in a number of materials, is provided by systems with a valence bond solid ground state, which exhibit a magnetic transition in the same universality class as Bose-Einstein condensation (BEC) in an applied magnetic field. Moreover, recent experiments on YbAl3C3 suggest that this compound may realize a magnon BEC transition in the presence of an itinerant conduction band. Motivated by these observations, we consider a one-dimensional two-leg spin ladder with a valence bond solid ground state doped with itinerant fermions. Using the Density Matrix Renormalization Group we study the system as a function of Kondo coupling, magnetic field and the density of itinerant fermions. In addition, we use analytical techniques to map out the phase diagram and study the critical properties, and compare limiting cases with the numerically exact DMRG results. We also discuss the application of our results to 2D and 3D systems. |
Monday, March 4, 2019 3:42PM - 3:54PM |
C07.00007: Magnetism and Electronic Correlations in Quasi-1D Kondo Lattices Filip Ronning, Tomoya Asaba, Eric Bauer, Joe D Thompson Reducing dimensionality is a powerful approach to increasing the influence of quantum fluctuations. Not only do quantum fluctuations become stronger in two- and one-dimensions, recent theoretical work using tools from quantum information science (tensor networks, etc.) allow exceedingly accurate studies of correlated electron systems in 1d. With this motivation we investigate quasi-1D 4f and 5f-based metallic compounds possessing non-trivial magnetic order. Using transport and thermodynamics we investigate the electronic and magnetic correlations in these systems and compare with theoretical understanding. |
Monday, March 4, 2019 3:54PM - 4:06PM |
C07.00008: Emergence of Kondo lattice behavior in a van der Waals itinerant ferromagnet Fe3GeTe2 Yun Zhang Searching for heavy fermion (HF) state in non-f electron systems becomes an interesting issue, especially in the presence of magnetism, and can help to unify the universal physics pictures in complex compounds. Here, using angle-resolved photoemission spectroscopy, scanning tunneling microscopy, physical properties measurements and the first-principles calculations, we observe the HF state in a 3d-electron van der Waals ferromagnet Fe3GeTe2. Upon entering the ferromagnetic state, a massive spectral weight transfer occurs, which results from the exchange splitting. Meanwhile, the Fermi surface volume and effective electron mass are both enhanced. When the temperature drops below a characteristic temperature T*, heavy electrons gradually emerge with further enhanced effective electron mass. The coexistence of ferromagnetism and HF state can be well interpreted by the dual properties (itinerant and localized) of 3d electrons. This work expands the limit of ferromagnetic HF materials from f- to d-electron systems and illustrates the positive correlation between ferromagnetism and HF state in the 3d-electron material, which is quite different from the f-electron systems. |
Monday, March 4, 2019 4:06PM - 4:18PM |
C07.00009: A new non-Fermi-liquid-like layered Cr boride Jack Simonson, Cristian Franco, Bingying Xia, Ryan Duke, Om Prakash, Meigan Aronson We report the discovery, the synthesis of large high quality single crystals, the crystal structure, and the basic properties of Cr4AlB4, a new member of the electrically conductive and damage tolerant MAB phase borides. Cr4AlB4 forms in a new orthorhombic structure-type in which slabs of Cr-B containing zig-zag chains of B are separated by nearly square planes of Al. Electrical resistivity measurements along the chain direction show a non-Fermi-liquid-like T3-dependence up to T ≈ 80 K, before becoming linear above T ≈ 150 K . We discuss these results in terms of magnetic and spectroscopic measurements and place this compound within the context of layered and quasi-one dimensional Cr-based systems. |
Monday, March 4, 2019 4:18PM - 4:30PM |
C07.00010: Charge dynamics and untapped redox potential in a Mn1+ - based electrode. Divyanshi Sar, S. Alexander Breitweiser, Ruimin Qiao, Ali Firouzi, Lin Miao, Rourav Basak, Shahrokh Motallebi, Christian Valencia, Mai Fujimoto, Colin Wessells, Hannah Israel, Yi-De Chuang, Wanli Yang, Lewis A Wray Manganese hexacyanomanganate (MnHCMn) with an unusual Mn1+ charged valence state has recently been identified as a promising sodium ion anode material, in spite of what appears to be an unfavorable closed-shell electron configuration. I will present an analysis of MnHCMn charge dynamics with bulk- and surface-sensitive soft X-ray absorption spectroscopy (sXAS) and resonant inelastic X-ray scattering (RIXS) at the Mn L3 edge. A charge transfer collective mode is observed, and found to represent the likely energy of the next charging redox plateau, which is yet unachieved in redox experiments. This reveals a unique capability that RIXS can provide for strongly correlated battery electrode materials, and suggests a significant untapped potential for MnHCMn anodes. |
Monday, March 4, 2019 4:30PM - 4:42PM |
C07.00011: Scanning Tunneling Microscopy and Spectroscopy on the Metallic Delafossite PdCoO2 DIBYASHREE CHAKRABORTI, Seunghyun Khim, Andrew Mackenzie, Peter Wahl The metallic delafossite PdCoO2 has risen to the limelight in the past few years [1]. Due to unusually long mean free paths, the electron fluid exhibits hydrodynamic effects [2].The anisotropic crystal structure leads to a quasi-2D character of the electronic states making the material suitable for surface sensitive techniques. Because of the polar nature of the surface, exciting physics is observed such giant Rashba spin-splitting [3] and itinerant ferromagnetism [4]. In our study, we have investigated the different surface terminations of PdCoO2 with low temperature Scanning Tunneling Microscopy. We will discuss their assignment and spectroscopic signatures. |
Monday, March 4, 2019 4:42PM - 4:54PM |
C07.00012: Collective Modes in SrTi1-xNbxO3 Measured with meV-Resolution EELS Samantha Rubeck, Melinda Rak, Matteo Mitrano, Ali Husain, Jin Chen, Alexander Edelman, Peter B Littlewood, Peter Abbamonte The emergence of superconductivity in low carrier solids does not follow the behavior of conventional BCS superconductivity. Niobium doped strontium titanate, SrTi1-xNbxO3, which becomes a superconductor at densities as low as 5.5×1017 cm-3 [1], is theorized to come about due to the hybridization of the longitudinal optic phonons with the plasmons. In this talk, I will present measurements of the collective charge excitations of SrTi1-xNbxO3 using momentum-resolved inelastic electron scattering (M-EELS). We observed a variety of acoustic and optic phonons in the range 0-200 meV that have been implicated in the superconducting pairing in this material. In addition, we observed an electronic mode at 25 meV that we identify as a valence plasmon from the Nb free carriers. I will discuss evidence for hybridization of these modes for different Nb concentration, x. |
Monday, March 4, 2019 4:54PM - 5:06PM |
C07.00013: Infrared nano-imaging of Luttinger liquid plasmons in single walled carbon nanotubes Sheng Wang, Feng Wang Quantum-confined electrons in one dimension (1D) constitute a Luttinger liquid, which features charge spin separation and other intriguing properties distinctly different from the Fermi liquid. Single walled carbon nanotubes (SWNTs) provide the ideal platform to explore such Luttinger liquid physics due to strong lateral quantum confinement and the presence of nanotubes of different species. But a systematic study of how the Luttinger liquid behaviors in carbon nanotubes depend on intrinsic and extrinsic factors such as chirality and doping has been lacking. We performed comprehensive infrared nano-imaging of Luttinger liquid plasmons in carbon nanotubes with different parameters and provide novel insights into Luttinger liquid physics in carbon nanotubes. This in-depth understanding of Luttinger liquid physics in SWNTs is not only of fundamental interests, but also pave the way for various nanophotonic applications based on carbon nanotubes. |
Monday, March 4, 2019 5:06PM - 5:18PM |
C07.00014: Investigation of Broken Time Reversal Symmetry in the Pr-rich side of Pr1-xNdxOs4Sb12 Pei-Chun Ho, Douglas E MacLaughlin, M Brian Maple, Lei Shu, Adrian Hillier, Oscar Bernal, Tatsuya Yanagisawa, P. K. Biswas, Jian Zhang, Cheng Tan, Shoji D Hishida, Taylor McCullough-Hunter One of the intriguing features that indicate unconventional superconductivity (SC) in the filled skutterudite compound PrOs4Sb12 is the broken time reversal symmetry (TRS). The preliminary analysis of our most-recent results of µSR experiments in Pr1-xNdxOs4Sb12 of x=0.05, 0.1, 0.15 and 0.2, at 0 magnetic field, a combined exponential and Gaussian relaxation behavior was found. As T decreases, the exponential rate λ increases, while the Gaussian rate Δ has a slight decrease below Tc. The increase of Δ below Tc, previously observed in PrOs4Sb12, is not seen for x≥0.05, indicating that TRS is no longer broken. λ here is expected to be mainly dynamic in nature and has a strong temperature dependence below Tc. λ grows with increasing x, which may be due to a quantum critical point or transition below 0.05K. The origin of the anomalous shape of λ(T) in TF-μSR below Tc for of x=0.15 and 0.2 is currently unknown. |
Monday, March 4, 2019 5:18PM - 5:30PM |
C07.00015: Tilted Weyl-Kondo Semimetal in Heavy Fermion Systems Sarah Grefe, Hsin-Hua Lai, Silke Paschen, Qimiao Si Recently we have introduced a time-reversal-symmetry (TRS) invariant periodic Anderson model on a noncentrosymmetric and nonsymmorphic lattice and demonstrated a Weyl-Kondo semimetal (WKSM) [1]. This strongly correlated, Kondo driven, topological semimetal phase has been evidenced in the recently discovered heavy fermion semimetal Ce3Bi4Pd3 [2]. In condensed matter systems without Lorentz invariance, a term that tilts the Weyl nodes is naturally present. In this study, we generalize the periodic Anderson model to realize a Tilted Weyl-Kondo Semimetal (TWKSM). We show how the tilted Weyl nodes allow for measurable properties that probe the topological nature of the TWKSM. |
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