Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session B27: Strongly Correlated Physics in d-electron Systems |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Christianne Beekman, Florida State University Room: 326 |
Monday, March 14, 2016 11:15AM - 11:27AM |
B27.00001: $\mu$SR study of the stoichiometric NbFe2 Daniel Margineda, Sean Giblin, Ross Stewart, Jon Duffy, Stephen Dugdale, Jon Taylor Quantum critical points (QCP) are important as understanding how fluctuating ground states can be lifted by novel correlated electron states such as unconventional superconductivity is not clear. $Nb_{1-y}Fe_{2+y}$ is a good candidate to investigate such criticality as it displays a rich-magnetic phase diagram and quantum criticality in a d-band metal. We investigate the magnetic ground state of stoichiometric $NbFe_2$ by bulk magnetisation and muon spin relaxation. Local magnetism clearly emerges below the critical temperature $T_N=10.3K$ and is dominated by quasi-static moments with an even distribution of magnetic fields $\Delta_{eff}$ ranging from 0 to $\sim140G$. A small moment of $M\sim0.02\mu_B/Fe$ is estimated, which is small because of the delocalised electronic distribution. In this work a stronger Curie-Weiss enhancement and an increased critical field suggests sample sensitivity to site mixing effects during the sample growth. Similar results are explained by a Spin Density Wave (SDW) with a large correlation length but the absence of oscillations cannot confirm this scenario: magnetic phase controlled by short-range interactions driven by Nb/Fe site mixing or an incommensurate helical SDW phase could both explain the field random orientation. [Preview Abstract] |
Monday, March 14, 2016 11:27AM - 11:39AM |
B27.00002: The Possibility of a Structural Quantum Critical Point in LaCu$_{6-x}$Au$_x$ L. Poudel, A. F. May, M. Koehler, C. de la Cruz, M. A. McGuire, S. Calder, V. Keppens, D. Mandrus, A. D. Christianson Understanding the critical phenomena near a quantum critical point (QCP) has attracted a substantial interest from the condensed matter physics community. Despite this interest, QCPs involving the zero temperature termination of a continuous structural phase transition remain largely unexplored. Here, we study the structural properties of the LaCu$_{6-x}$Au$_x$ series, which appears to be an ideal candidate to exhibit a SQCP. The orthorhombic-monoclinic transition temperatures in LaCu$_{6-x}$Au$_x$ decrease with Au-composition until a complete suppression of the monoclinic phase occurs at the SQCP, $x = 0.3$. The lattice component of the low-temperature heat capacity exhibits a maximum at the critical concentration, providing a further indication of the presence of a SQCP in the LaCu$_{6-x}$Au$_x$ series. [Preview Abstract] |
Monday, March 14, 2016 11:39AM - 11:51AM |
B27.00003: Evolution of Quantum Critical Behavior In A Concentrated Ternary Solid Solution: NiCoCr$_{x\, }$ Brian Sales, Ke Jin, Hongbin Bei, Malcolm Stocks, German Samolyuk, Andrew May, Michael McGuire The face centered cubic (fcc) alloy NiCoCr$_{x}$ with x near 1 is found to be close to the Cr concentration where the ferromagnetic transition temperature, T$_{c}$ goes to 0. Near this composition these alloys exhibit a resistivity linear in temperature to 2 K, a perfectly linear magnetoresistance, and an excess -TlnT contribution to the low temperature heat capacity. As the Cr concentration is decreased from 1, the Curie temperature and the saturation magnetization, M$_{0}$, both increase exponentially with x. For x $=$ 0.5, T$_{c}\approx $ 217 K, but M$_{0}$ is only 0.26 Bohr magnetons/atom, indicating highly itinerant ferromagnets for 0.5 \textless x \textless 0.8. All of the low temperature electrical, magnetic and thermodynamic properties of the alloys with compositions near x$=$1 are not typical of a Fermi liquid and suggest strong magnetic fluctuations associated with a quantum critical region. This new class of concentrated solid solution fcc alloys are ideal model systems to study the effects of chemical disorder on emergent properties near a quantum critical point. Research supported by the DOE Office of Science, Materials Science and Engineering Division, and the Energy Dissipation to Defect Evolution EFRC. [Preview Abstract] |
Monday, March 14, 2016 11:51AM - 12:03PM |
B27.00004: Finite mass enhancement across bandwidth controlled Mott transition in NiS$_{2-x}$Se$_{x}$ Garam Han, W. S. Kyung, Y. K. Kim, C. M. Cheng, K. D. Tsuei, K. D. Lee, N. Hur, H.-D. Kim, C. Kim One of the most important and still debated issues in the strongly correlated electron systems is on the metal insulator transition (MIT) mechanism. In the bandwidth controlled Mott transition (BCMT) scenario, which Mott originally proposed, MIT occurs through a mass divergence in which the effective mass of the quasi-particle (QP) diverges approaching the MIT. The interpretation is supported by dynamic mean field theory (DMFT) model calculations. However, few direct observations have been made yet due to various experimental restrictions. In this talk, I present systematic angle resolved photoemission studies on the MIT in NiS$_{2-x}$Se$_{x}$,$_{\, }$which is a well-known BCMT material. We observed not only the bandwidth shrinkage but also the coherent quasi-particle peak (QP) which is not of the surface origin. In addition, we experimentally showed the mass of the QP remains finite approaching the MIT. [Preview Abstract] |
Monday, March 14, 2016 12:03PM - 12:15PM |
B27.00005: Revealing the electronic ground state of ReNiO$_{3}$ combining Ni-L$_{3}$ x-ray absorption and resonant inelastic x-ray scattering Valentina Bisogni, Sara Catalano, Robert Green, Marta Gibert, Raoul Scherwitzl, Yaobo Huang, Shadi Balandesh, Vladimir N. Strocov, Pavlo Zubko, George Sawatzky, Jean-Marc Triscone, Thorsten Schmitt Rare-earth nickelates ReNiO$_{3}$ attract a lot of interest thanks to their intriguing physical properties like sharp metal to insulator transition, unusual magnetic order and expected superconductivity in nickelate-based heterostructures. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). Taking a NdNiO$_{3}$ thin film as a representative example, we reveal with x-ray absorption and resonant inelastic x-ray scattering unusual coexistence of bound and continuum excitations, providing strong evidence for abundant O 2p holes in the GS of these materials. Using an Anderson impurity model interpretation, we show that these distinct spectral signatures arise from a Ni 3d$^{8}$ configuration along with holes in the O 2p valence band, confirming suggestions that these materials exhibit a negative charge-transfer energy, with O 2p states extending across the Fermi level. [Preview Abstract] |
Monday, March 14, 2016 12:15PM - 12:27PM |
B27.00006: Polyanion Driven Antiferromagnetic and Insulating Ground State of Olivine Phosphates: LiMPO$_{4}$. Ajit Kumar Jena, B. R. K. Nanda Through density functional calculations we have investigated the electronic and magnetic properties of LiMPO$_{4}$, where M is a 3d transition metal element. We find that contrary to many transition metal oxides, in these Olivine phosphates the band gap is originated due to crystal field anisotropy as well as weak O-p -- M-d covalent interaction. Both of them are attributed to the presence of PO$_{4}^{3-}$ polyanion. The anisotropic crystal field, in the absence of covalent interactions, creates atomically localized non-degenerate M-d states and therefore the gap is a natural outcome. Onsite repulsion, due to strong correlation effect, further enhances the gap. These localized d states favor high-spin configuration which leads to antiferromagnetic ordering due to Hund's coupling. Experimentally observed low Neel temperature of this family of compounds is explained from the DFT obtained spin exchange interaction parameters. [Preview Abstract] |
Monday, March 14, 2016 12:27PM - 12:39PM |
B27.00007: \textbf{\textit{Ab initio}}\textbf{ quantum Monte~Carlo calculations of ground-state properties of manganese's oxides} Vinit Sharma, Jaron T. Krogel, P.R.C. Kent, Fernando A. Reboredo One of the critical scientific challenges of contemporary research is to obtain an accurate theoretical description of the electronic properties of strongly correlated systems such as transition metal oxides and rare-earth compounds, since state-of-art ab-initio methods based on approximate density functionals are not always sufficiently accurate. Quantum Monte~Carlo (QMC) methods, which use statistical sampling to evaluate many-body wave functions, have the potential to answer this challenge. Owing to the few fundamental approximations made and the direct treatment of electron correlation, QMC methods are among the most accurate electronic structure methods available to date. We assess the accuracy of the diffusion Monte Carlo method in the case of rocksalt manganese oxide (MnO). We study the electronic properties of this strongly-correlated oxide, which has been identified as a suitable candidate for many applications ranging from catalysts to electronic devices. "This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division." [Preview Abstract] |
Monday, March 14, 2016 12:39PM - 12:51PM |
B27.00008: Angle resolved photoemission spectroscopy and X-ray diffraction study on IrTe1.6Se0.4 D.-H. Kim, K.-T. Ko, Kyoo Kim, J.-H. Park, B.-G. Park, T.-Y. Koo, J.-J. Yang, S.-W. Cheong IrTe2 shows an interesting phase transition accompanying $\mathbf{q} = (1/5, 0, 1/5)$ lattice distortion, Ir valence fluctuation, and $J_{eff} = 1/2$ dimer formation. In order to study the role of anion doping, we investigated IrTe$_{1.6}$Se$_{0.4}$ which is known to exhibit $\mathbf{q} = (1/6, 0, 1/6)$ lattice distortion and higher transition temperature, about 370 K. The electronic structure of IrTe$_{1.6}$Se$_{0.4}$ single crystal was investigated by using angle resolved photoemission spectroscopy before and after the dimerization transition, which displays abrupt changes. Ir valence, investigated by corelevel X-ray photoemission, varies continuously from a pure Ir$^{3+}$ state to Ir$^{4+}$:Ir$^{3+} \simeq 1:1$ state, while x-ray diffraction measurement reveals a first order structure transition. In this talk, we will discuss an implication of our observations. [Preview Abstract] |
Monday, March 14, 2016 12:51PM - 1:03PM |
B27.00009: Consequences of breaking time reversal symmetry in LaSb: a resistivity plateau and extreme magnetoresistance Fazel Tafti, Quinn Gibson, Satya Kushwaha, Neel Haldolaarachchige, Robert Cava Time reversal symmetry protects the metallic surface modes of topological insulators (TIs). The transport signature of robust metallic surface modes of TIs is a plateau that arrests the exponential divergence of the insulating bulk with decreasing temperature. This universal behavior is observed in all TI candidates ranging from Bi$_{\mathrm{2}}$Te$_{\mathrm{2}}$Se to SmB$_{\mathrm{6}}$. Recently, several topological semimetals (TSMs) have been found that exhibit extreme magnetoresistance (XMR) and TI universal resistivity behavior revealed only when breaking TRS, a regime where TIs theoretically cease to exist. Amongst these new materials, TaAs and NbP are nominated for Weyl semimetal due to their lack of inversion symmetry, Cd$_{\mathrm{3}}$As$_{\mathrm{2}}$ is nominated for Dirac semimetal due to linear band crossing, and WTe$_{\mathrm{2}}$ is nominated for resonant compensated semimetal due to perfect electron-hole symmetry. Here we introduce LaSb, a simple rock-salt structure material without broken inversion symmetry, without perfect linear band crossing, and without perfect electron-hole symmetry. Yet LaSb portrays all the exotic field induced behaviors of the aforementioned semimetals. It shows the universal TI resistivity with a plateau at 15 K, revealed by a magnetic field, ultrahigh mobility of carriers, quantum oscillations with 2D Fermi surface, and XMR of about one million percent. Due to its dramatic simplicity, LaSb is the ideal model system to formulate a theoretical understanding of the exotic consequences of breaking TRS in TSMs. [Preview Abstract] |
Monday, March 14, 2016 1:03PM - 1:15PM |
B27.00010: Low-energy Electrodynamics of non-Drude Transport in the Strongly Correlated Ferromagnetic Metal SrRuO$_3$ Youcheng Wang, G. Bosse, Y. Lubashevsky, J. P. Sheckelton, D. E. Shai, C. Adamo, D.G. Schlom, K. M. Shen, N. P. Armitage While the highly correlated complex oxide perovskite ferromagnet SrRuO$_3$ has been studied for decades, interest remains in its unusual transport properties. Here we report time-domain THz conductivity measurements taken from room temperature down to 1.5$\,$K on a low disorder film of SrRuO$_3$. Previous optical measurements have shown a deviation from Drude-like transport in this material. We investigate these deviations using an extended Drude model analysis and find evidence for an effective non-Fermi liquid-like behavior in the frequency dependence of the scattering rate. The high quality of our film, reflected in its large residual resistivity ratio, allows us to better isolate the inelastic scattering channels. We have also extended these experiments down to the microwave regime and in this context investigate possible origins of this non-Drude transport, including the possibility of very low frequency interband transitions that are caused by small octahedral rotations and tilting that are inherent in the class of materials. [Preview Abstract] |
Monday, March 14, 2016 1:15PM - 1:27PM |
B27.00011: Surface Broken Symmetry on Orthorhombic Double-layer Sr$_{3}$(Ru$_{1-x}$Mn$_{x})_{2}$O$_{7}$ Chen Chen, V. B. Nascimento, Zhenyu Diao, Jiandi Zhang, Rongying Jin, E. W. Plummer The surface of double-layered ruthenate Sr$_{3}$Ru$_{2}$O$_{7}$ exhibits octahedra tilt distortion and an enhanced rotational distortion caused by the broken symmetry. Previous LEED IV calculation reveals that the tilt angle is (2.5\textpm 1.7)\textdegree at 80 K (B. Hu \textit{et. al.}, Physical Review B 81, 184104 (2010)). A glideline symmetry and a mirror symmetry along this direction are both broken. Results from LEED IV simulations show that both broken symmetries originate from the emergence of surface tilt. The degree of broken symmetry is more sensitive to the tilt angle, thus producing a smaller error than from conventional LEED IV calculation. When Mn doping is induced into the compound, the tilt is removed and the symmetry of the LEED pattern returns to what is expected for rotation, two glide planes and four-fold symmetry. [Preview Abstract] |
Monday, March 14, 2016 1:27PM - 1:39PM |
B27.00012: Band dependent magneto thermoelectric measurements on Ca$_3$Ru$_2$O$_7$ Hui Xing, Chenyi Shen, Libin Wen, Jiaming He, Shun Wang, Jin Peng, Jianjian Ge, Youming Zou, Mingliang Tian, Zhuan Xu, Zhiqiang Mao, Ying Liu Ca$_3$Ru$_2$O$_7$ features a Neel transition at 56 K followed by a structure and metal-insulator transition at 48 K as the temperature is lowered, suggesting a complex structure-property relationship driven by electron correlated effects. However, the electronic states of Ca$_3$Ru$_2$O$_7$ are not understood. ARPES measurements revealed the presence of an electron Fermi arc, while the expected hole Fermi arc is missing. Quantum oscillations showed the existence of a small Fermi surface, but the details of the Fermi surface, including whether the hole Fermi arc is present, are not determined. We performed band-dependent thermoelectric measurement with the temperature gradient directed to a specific crystalline axis. Magneto thermopower along crystalline a and b axes, S$_a$ and S$_b$, both of which are negative in sign and nearly identical at high temperatures, were found to behave markedly differently below the metal-insulator transition, with S$_b$ changing its sign from being negative to positive. Our analysis suggests that S$_a$ and S$_b$ in Ca$_3$Ru$_2$O$_7$ are dominated by the electron and hole Fermi arcs, respectively. The implications of our data on the physics of Ca$_3$Ru$_2$O$_7$ will be discussed. [Preview Abstract] |
Monday, March 14, 2016 1:39PM - 1:51PM |
B27.00013: Quasi-continuum excitation in Co-doped CaRuO3. Jagath Gunasekera, Ashutosh Dahal, Jose Rodriguez, Leland Harriger, Tom Heitmann, Deepak Singh Spin-1/2 systems provide a unique platform to study the interplay between magnetism and quantum mechanics that often depict novel properties, such as quantum spin liquid or singlet-to-triplet transition. In this presentation, we report an interesting observation of singlet-to-triplet transition in Co-doped CaRuO3, even though none of the magnetic atoms (Co or Ru) exhibit spin-1/2 properties. What we have found that as Co atom gradually replaces Ru in CaRuO3, the system tends to develop a localized excitation around Q$=$1 A$^{-1}$ at 5.9 meV at low temperature. At roughly 20{\%} doping percentage of Co, the inelastic excitation at low temperature is well described by singlet-to-triplet transition of S$=$1/2. As the measurement temperature increases, the localized excitation fades into a sort of Q-independent background that becomes stronger as a function of temperature. This behavior is also well manifested by ac susceptibility measurements where the dynamic susceptibility tends to get stronger as the temperature increases. Our analysis suggests that Co-doping in CaRuO3 locally creates 3$d^{7}$ electronic configuration, which can be described by S$=$1/2 in this disordered system. [Preview Abstract] |
Monday, March 14, 2016 1:51PM - 2:03PM |
B27.00014: Electronic correlation effects in SrRuO3 ultra-thin films Liang Si, Zhicheng zhong, Oleg Janson, Gang Li, Jan Tomczak, Karsten Held SrRuO3 (SRO) is a ferromagnetic metal with an appreciably high Curie-temperature of 160 K and a ferromagnetic moment of 0.8-1.6 uB/Ru. Recent experimental studies on SRO thin films show that both electronic and magnetic ground states drastically depend on the nature of the surface. Ultra-thin (001)-oriented films are insulating and lack ferromagnetism, while in (111)-oriented films ferromagnetic moments and Tc are enhanced compared with bulk. Here we investigate SRO films by density functional theory (DFT)+U and DFT+dynamical mean-field theory (DMFT). In agreement with the experiments, we find that metallic ferromagnetism in SRO (001)-oriented films vanishes below a certain critical layer thickness. We propose a new route for tuning the properties of these thin films and show that room temperature ferromagnetism can be attained by electron doping. For the SRO (111)-oriented thin films, we find that the enhanced Tc is facilitated by electronic correlation effects and the geometric confinement. The experimentally observed enhancement of ferromagnetic moments in SRO(111)-oriented thin films is addressed by considering the stability of the high-spin Ru state in the presence of oxygen vacancies. Finally, the topological properties of SRO (111)-oriented bilayers will be discussed. [Preview Abstract] |
Monday, March 14, 2016 2:03PM - 2:15PM |
B27.00015: Ambipolar transport in the field-suppressed superconducting state of quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$ Joshua L. Cohn, Carlos A. M. dos Santos, John J. Neumeier We present resistivity, Hall, Seebeck, and Nernst coefficient measurements in the range $0.4~K\leq T\leq 20$~K on single crystals of the quasi-one-dimensional (Q1D) metal, Li$_{0.9}$Mo$_6$O$_{17}$ with current along the Q1D metallic chains. At temperatures below the nominal superconducting transition temperature ($T_c=2$~K), a transition from hole-like ($\mu_0H< 1$~T) to electron-like ($\mu_0H\geq 2$~T) behavior is evidenced in the magnetotransport coefficients. Possible insights from these results into the nature of the mysterious density-wave order$^{a,b}$ responsible for the upturn in resistivity below $\sim 25$~K will be discussed. \vskip .1in \noindent $^a$ C. A. M. dos Santos {\it et al.}, Phys. Rev. Lett. {\bf 98}, 266405 (2007). \vskip .1in \noindent $^b$ X. Xu \emph{et al.}, Phys. Rev. Lett. {\bf 102}, 206602 (2009). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700