Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session J43: Heavy Fermion Actinide Metals and SuperconductorsLive

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Sponsoring Units: DCMP Chair: Narayan Poudel, Idaho National Laboratory 
Tuesday, March 16, 2021 3:00PM  3:12PM Live 
J43.00001: Bypassing the computational bottleneck of quantumembedding theories for strong electron correlations with machine learning John Rogers, TsungHan Lee, Sahar Pakdel, Wenhu Xu, Vladimir Dobrosavljevic, Yongxin Yao, Ove Christiansen, Nicola Lanata A cardinal obstacle to performing quantummechanical simulations of stronglycorrelated matter is that, with the theoretical tools presently available, sufficientlyaccurate computations are often too expensive to be ever feasible. Here we design a computational framework combining quantumembedding (QE) methods with machine learning. This allows us to bypass altogether the most computationallyexpensive components of QE algorithms, making their overall cost comparable to bare Density Functional Theory. We perform benchmark calculations of a series of actinide systems, where our method describes accurately the correlation effects, reducing by orders of magnitude the computational cost. We argue that, by producing a largerscale set of training data, it will be possible to apply our method to systems with arbitrary stoichiometries and crystal structures, paving the way to virtually infinite applications in condensed matter physics, chemistry and materials science. 
Tuesday, March 16, 2021 3:12PM  3:24PM Live 
J43.00002: LandauGinzburg Theory of Tetragonal Hastatic Order: Application to URu_{2}Si_{2} Milan Kornjaca, Rebecca Flint Hidden order in URu_{2}Si_{2} remains a compelling mystery long after its discovery. We revisit the hastatic order proposal of spinorial hybridization within LandauGinzburg theory. Rather than a single spinorial order parameter breaking doubletimereversal symmetry, we find two vectorial orders: the expected composite order with onsite moments, and a new quantity capturing symmetries broken solely by the spinorial nature. We also address the effect of fluctuations and disorder on the tetragonal symmetry breaking, explaining the absence of inplane moments and predicting transitions in transverse field. 
Tuesday, March 16, 2021 3:24PM  3:36PM Live 
J43.00003: Origin of gaplike behaviors in URu_{2}Si_{2}: Combined study via quasiparticle scattering spectroscopy and resistivity measurements Shengzhi Zhang, Greta Chappell, Naveen Pouse, Ryan Baumbach, M Brian Maple, Laura H H Greene, Wan Kyu Park What are the distinct roles played by the localized and itinerant electrons in the hidden order transition of URu_{2}Si_{2}? We will show that the hybridization gap observed via quasiparticle scattering spectroscopy shows minimal change upon crossing the phase boundary in the entire phase space of URu_{2}Si_{2x}P_{x} and URu_{2y}Fe_{y}Si_{2 }[1,2,3]. This suggests its opening is not associated with the ordering. Thus, localized electrons must be the major player. Furthermore, we provide a consistent explanation for the origin of gaps observed only in the ordered states. Taking the gapped bosonic excitations as the dominant scattering source [4], all of our resistivity data including the jump at the transition are replicated. The extracted gap increases with increasing Fe content, similar to the E_{1} gap in inelastic neutron scattering [5], suggesting a common origin. 
Tuesday, March 16, 2021 3:36PM  3:48PM Live 
J43.00004: An Anisotropic Enhancement of Spin Orbit Coupling in the Underscreened Anderson Lattice Model Peter Riseborough, Xiao Yuan The underscreened Anderson Lattice Model describes the uranium monochalcogenides, US, USe and UTe which at high temperatures, the Curie susceptibility show large magnetic moments, and the resistivities show lograithmic temperature variations indicative of a Kondo Effect. At lower temperatures, the magnetic moments are only partially compensated and the residual moments undergo transitions to ferromagnetic states. We examine the effect that the Coulomb and Hund's Rule exchange interaction have on the enhancement of the spinorbit coupling in the Underscreened Anderson Lattice Model. We assume invariance under timereversal and inversion. Within a rotationally invariant framework, we consider spin and orbital rotationally invariant interactions and an anisotropic crystal structure, and show that the spinorbit coupling is enhanced and becomes anisotropic. The results are related to the unsual magnetic anisotropy observed in the ferromagnetic states of the cubic uranium monochalcogenides, 
Tuesday, March 16, 2021 3:48PM  4:00PM Live 
J43.00005: Electronic structure of ferromagnetic superconductor UGe_{2} in comparison to UTe_{2} Jonathan Denlinger, James W Allen, Andrew D. Huxley, Jacques Flouquet The newly discovered spintriplet superconductor UTe_{2} [1] has a strong suggestive relationship to the family of ferromagnetic superconductors UGe_{2}, URhGe and UCoGe. Here we update studies [2] of the electronic bandstructure of UGe_{2}, experimentally measured by angleresolved photoemission (ARPES) near the U 5d5f resonance, with comparisons to DFT calculations of ThGe_{2} decomposed into subunit building block structures. A signature imprint of a 2D diagonal squarenet plane of Ge atoms on the formation of large diamondshaped Fermi surface contours is shown to agree well with ARPES and with dHvA orbit sizes. Similar theoretical decomposition of the UTe_{2} structure into zigzag UTe chains and a plane of Te linear chains with strong porbital bondingantibonding splitting identifies the origins of the underlying orthogonal quasi1D band structures near the Fermi level, in agreement with recent ARPES measurements [3]. 
Tuesday, March 16, 2021 4:00PM  4:12PM Live 
J43.00006: Thermal expansion and magnetostriction of UTe2 Kristin Willa, Frederic Hardy, Georg Knebel, Dexin Li, William Knafo, Dai Aoki, Jacques Flouquet, Christoph Meingast, Gerard Lapertot

Tuesday, March 16, 2021 4:12PM  4:24PM Live 
J43.00007: Resonant Ultrasound Studies on the TimeReversal Symmetry Breaking Superconductor Candidate UTe_{2} Florian Theuss, Gael Grissonnanche, Sheng Ran, Johnpierre Paglione, Nicholas Butch, Brad Ramshaw UTe_{2} is a promising candidate for a timereversal symmetry (TRS) breaking superconductor. Since the recent discovery of its superconducting state below 1.6 K, several studies have established its spintriplet character (e.g. a high upper critical field, and a negligible change in the Knight shift across T_{c}). A field trainable Kerr rotation even indicated TRS breaking of the superconducting order parameter. Because TRSbreaking superconductivity requires a twocomponent order parameter, and because UTe_{2} is orthorhombic, two separate superconducting transitions are expected. Two transitions have indeed been observed in heat capacity measurements. However, these findings are heavily debated. We investigate the possibility of two superconducting transitions with resonant ultrasound spectroscopy and look into what this can tell us about twocomponent order parameters. 
Tuesday, March 16, 2021 4:24PM  4:36PM Live 
J43.00008: Itinerant spin fluctuations in antiferromagnetic heavyfermion system U_{2}Zn_{17} Yishu Wang, Hyowon Park, Daniel Pajerowski, Andrei Savici, Jose A. RodriguezRivera, Zachary Fisk, Collin Leslie Broholm We report an inelastic neutron scattering investigation of the heavyfermion system U_{2}Zn_{17}. Covering the energy range from 0.1 to 10meV, we document a continuum of magnetic scattering localized in reciprocal space around magnetic Bragg peaks. In particular, no coherent spinwave excitation are apparent for T=0.3 K and E>0.1meV, despite longrange antiferromagnetic order for T<T_{N}=9.7K with an ordered moment of μ=0.8μ_{Β}/U. At elevated temperature well above T_{N}, the spectrum remains mostly unchanged though broadened in reciprocal space. U_{2}Zn_{17} thus represents a unique model system that has no regime of coherent spin waves as in a collinear insulating AFM. Our comprehensive neutron scattering data motivates a DFT+DMFT calculation to quantitatively address the strong correlation effect, which also gives rise to the large Sommerfeld coefficient γ~200mJ/(mole K^{2}) in the ordered state. 
Tuesday, March 16, 2021 4:36PM  4:48PM Live 
J43.00009: Quantum Critical Behavior in the Disordered Itinerant Ferromagnet UCo_{1x}Fe_{x}Ge Sangyun Lee, Eric D Bauer, Filip Ronning, Joe Thompson, Priscila Rosa, Roman Movshovich

Tuesday, March 16, 2021 4:48PM  5:00PM Live 
J43.00010: Magnetic Confinement of SpinTriplet Superconductivity WenChen Lin, Daniel J Campbell, Sheng Ran, ILin Liu, Hyunsoo Kim, Andriy Nevidomskyy, David E Graf, Nicholas Butch, Johnpierre Paglione Electrical magnetoresistance and tunnel diode oscillator measurements were performed under external magnetic fields up to 41T applied along the crystallographic b axis (hard axis) of UTe_{2} as a function of temperature and applied pressures up to 18.8kbar. In this work, we track the fieldinduced firstorder transition between superconducting and magnetic fieldpolarized phases as a function of applied pressure, showing suppression of the transition with increasing pressure until the demise of superconductivity near 16kbar and the appearance of a pressureinduced ferromagneticlike ground state that is distinct from the fieldpolarized phase and stable at zero field. Together with evidence for the evolution of a second superconducting phase and its upper critical field with pressure, we examine the confinement of superconductivity by two orthogonal magnetic phases and the implications for understanding the boundaries of triplet superconductivity. 
Tuesday, March 16, 2021 5:00PM  5:12PM Live 
J43.00011: Spin susceptibility in the superconducting state of UTe_{2} probed with ^{125}TeNMR Kenji Ishida, Genki Nakamine, Shunsaku Kitagawa, Katsuki Kinjo, Yo Tokunaga, Hironori Sakai, Shinsaku Kambe, Ai Nakamura, Yusei Shimizu, Yoshiya Homma, Dexin Li, Fuminori Honda, Dai Aoki To investigate spin susceptibility in a superconducting (SC) state, we measured the ^{125}Tenuclear magnetic resonance (NMR) Knight shifts at magnetic fields (H) along the b and c axes of singlecrystal UTe_{2}, a promising candidate for a spintriplet superconductor. In the SC state, the Knight shifts along the b and c axes (K_{b} and K_{c}, respectively) decreased slightly and the decrease in K_{b} was almost constant up to 7T. The reduction in K_{c} decreased with increasing H, and K_{c} was unchanged through the SC transition temperature at 5.5 T, excluding the possibility of spinsinglet pairing. Our results indicate that spin susceptibilities along the b and c axes slightly decrease in the SC state in low H, and the H response of SC spin susceptibility is anisotropic in the bc plane. We discuss the possible dvector state within the spintriplet scenario and suggest that the dominant dvector component for the case of H  b changes above 13 T, where T_{c} increases with increasing H. 
Tuesday, March 16, 2021 5:12PM  5:24PM Live 
J43.00012: An Optical Investigation of the normal state of UTe_{2} Sirak Mekonen, ChangJong Kang, Dipanjan Chaudhuri, David Barbalas, Sheng Ran, Gabriel Kotliar, Nicholas Butch, Peter Armitage The recently discovered unconventional superconductor, UTe_{2}, has attracted immense scientific interest due to the experimental observations that suggest spintriplet pairing. The normal state of UTe_{2} behaves like a Kondo lattice metal. Here, we have studied the optical properties of the normal state of UTe_{2} at frequencies between 10cm^{1} and 8500 cm^{1} and temperatures between 5 and 290 K using conventional Fourier Transform Infrared Reflectivity. From the measured reflectivity, we have directly determined the complex optical conductivity. The frequency dependence of the real part of the optical conductivity show maximum peaks around 4000cm^{1}with the 50 K revealing the highest conductivity. DFT + DMFT calculations supports the experimental findings and attribute the optical conductivity to an intraband transitions of a coherent U 5f feature near the Fermi level. 
Tuesday, March 16, 2021 5:24PM  5:36PM Live 
J43.00013: Electronic tuning in URu_{2}Si_{2} through Ru to Pt chemical substitution Greta Chappell, William Nelson, David E Graf, Ryan Baumbach Tuning studies that control the unit cell volume and electronic composition have been particularly useful in understanding what factors lead to hidden order (HO) and superconductivity in the strongly correlated electron system URu_{2}Si_{2} [1]. Several unifying trends have emerged with chemical substitutions that qualitatively adds electrons (e.g., Ru → Rh and Si → P), such as, the rapid destruction of HO, even as the underlying Kondo lattice is preserved, and the emergence of complex magnetism with large substitutions. An understanding of what factors differentiate the regions in this generic electron doping phase diagram will likely clarify the mechanisms which are necessary for producing HO. In order to examine whether these trends persist for an even more dissimilar substituent, we developed the series U(Ru_{1x}Pt_{x})_{2}Si_{2}. We will present thermodynamic and electrical transport measurements for this series and discuss the notable similarities to other phase diagrams. 
Tuesday, March 16, 2021 5:36PM  5:48PM Live 
J43.00014: Revisiting the properties of the heavyfermion superconductor UBe_{13} via polycrystalline samples Primoz Kozelj, Martin Juckel, Ulrike Stockert, Markus König, Andreas LeitheJasper, Yuri Grin, Elena Hassinger, Eteri Svanidze The unconventional superconducting behavior of UBe_{13} is still an active research topic [1, 2], despite it being one of the first reported heavyfermion superconductors [3]. Recently it was shown [4] that the physical properties of single crystals grown from Al flux – a method that was available from the very outset [3] – are significantly affected by Al incorporation into the lattice even though the amount is rather small (< 12 at. %). This contribution will present an alternative way in which polycrystalline samples can be used to gain insight into the intrinsic properties of UBe_{13}. By concentrating on polycrystalline samples, we completely avoid the problem of Al inclusions and thus examine the effect of the inherent crystallographic defects (both at the atomic and the microscale) in UBe_{13} on the critical temperature T_{c}, the Sommerfeld coefficient γ, and the size of the specific heat anomaly. 
Tuesday, March 16, 2021 5:48PM  6:00PM Live 
J43.00015: Probing electronic anisotropy in the normal state of UTe_{2} Yun Suk Eo, Hyunsoo Kim, Sheng Ran, Jarryd Horn, Halyna Hodovanets, Shanta Saha, John Collini, Wesley T Fuhrman, Andriy Nevidomskyy, Nicholas Butch, Michael S Fuhrer, Johnpierre Paglione We study the temperature dependence and the magnetic field dependence of electrical resistivity for currents directed along all crystallographic axes in the normal state of the spintriplet superconductor UTe_{2}. First, we focus on an accurate determination of the resistivity by using transport geometries that allow the extraction of two resistivities along with the primary axes directions. Next, we focus on the magnetotransport properties. We compare our transport results with the recent band calculations and ARPES reports. 
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