Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session F19: Heavy Fermions and Quantum Criticality in 115's |
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Sponsoring Units: DCMP Chair: Johnpierre Paglione, University of Maryland Room: 321 |
Tuesday, March 19, 2013 8:00AM - 8:12AM |
F19.00001: The electronic structure of Ce-based 115's Filip Ronning, Yusuke Nomura, Ryotaro Arita, Hiroaki Ikeda, Anton Kozhevnikov, Jianxin Zhu The Ce and Pu-based 115's embody the notion that reduced dimensionality and increased spin fluctuation energy scales are good for unconventional superconductivity. Often these materials are considered to be quasi two-dimensional systems similar in spirit to the high temperature cuprate superconductors. However, in reality the systems are rather three dimensional. Consequently, we construct an accurate down-folded Hamiltonian from ab-initio electronic structure calculations for the Ce-based 115 materials. We subsequently perform a constrained RPA calculation to obtain effective Coulomb parameters as a starting point to further investigate the magnetic, superconducting, and heavy fermion phenomena which these materials possess. [Preview Abstract] |
Tuesday, March 19, 2013 8:12AM - 8:24AM |
F19.00002: Stability of the Kondo Lattice and Field-tuned Antiferromagnetic Structures in the Ce$_{1-x}$Yb$_x$RhIn$_5$ System Sooyoung Jang, Benjamin White, Marc Janoschek, Brian Maple We have investigated the series Ce$_{1-x}$Yb$_x$RhIn$_5$ (0 $\leq x \leq$ 0.8) by means of x-ray diffraction, energy dispersive x-ray spectroscopy, electrical resistivity ($\rho$), specific heat ($C$), and magnetic susceptibility measurements. The coherence temperature $T$$_{coh}$ inferred from $\rho(T)$ remains nearly constant over a wide range of Yb concentrations 0 $\leq x \leq$ 0.8. Measurements of $C(T)$ were made in various magnetic fields up to 9 tesla on the Ce$_{1-x}$Yb$_x$RhIn$_5$ samples. In CeRhIn$_5$, the peak in $C(T)$ associated with the incommensurate antiferromagnetic (AFM) transition is accompanied by another peak that is associated with the commensurate AFM transition that emerges in an applied magnetic fields. Measurements on Ce$_{1-x}$Yb$_x$RhIn$_5$ samples ($x$ = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) reveal that the field induced commensurate AFM peak shifts relative to the incommensurate peak with Yb substitution. The results indicate that Yb substitution stabilizes the electronic state and tunes the AFM structures in Ce$_{1-x}$Yb$_x$RhIn$_5$. [Preview Abstract] |
Tuesday, March 19, 2013 8:24AM - 8:36AM |
F19.00003: London penetration depth in Ce$_{1-x}$Yb$_x$CoIn$_5$ ($0 \le x \le 0.4$) Hyunsoo Kim, Makariy A. Tanatar, Ruslan Prozorov, Benjamin D. White, Ivy K. Lum, M. Brian Maple The London penetration depth was measured in single crystals of superconducting Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$ ($0\leq x\leq0.4$) by means of a tunnel diode resonator technique operating at 15 MHz in a dilution refrigerator down to 100 mK. Judging from the suppression of the superconducting transition temperature, the superconductivity in CeCoIn$_{5}$ is relatively robust to Yb - substitution on Ce site unlike the substitution with other rare earth elements. On the other hand, the Yb substitution induces a drastic change of the Fermi surface near $x=0.2$, from which one may expect a significant change in properties of superconducting pairing upon doping. Possible evolution of superconducting order parameter in Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$ with increasing $x$ will be discussed based on the results from penetration depth measurements. \\ \\ Work in Ames was supported by the Department of Energy Office of Science, Basic Energy Sciences under Contract No. DE-AC02-O7CH11358. Work in San Diego was supported by the Department of Energy Office of Science (Grant DE-FG02-04-ER46105). [Preview Abstract] |
Tuesday, March 19, 2013 8:36AM - 8:48AM |
F19.00004: Non-Fermi liquid behavior with and without quantum criticality in Ce$_{\mathrm{1-x}}$Yb$_{\mathrm{x}}$CoIn$_5$ Y.P. Singh, T. Hu, L. Shu, M. Janoschek, M. Dzero, M.B. Maple, C.C. Almasan In a growing number of f-electron systems the non-Fermi liquid (NFL) behavior occurs in the absence of an obvious quantum phase transition (QPT), which takes place at a quantum critical point (QCP). An intriguing candidate is Ce$_{\mathrm{1-x}}$Yb$_{\mathrm{x}}$CoIn$_5$ that exhibits an unconventional T -- x phase diagram without an apparent QCP. Therefore, it is important to elucidate the nature of the NFL behavior and to search for possible QCPs in this system Here we reveal a field induced QCP (H$_{\mathrm{QCP}})$ through normal state magneto-resistivity measurements and find its evolution with x. The full suppression of H$_{\mathrm{QCP}}$ for x \textgreater\ 0.2 has surprisingly little effect on the Kondo lattice coherence. At low Yb concentrations, resistivity consists of two contributions with linear and sub-linear temperature dependences, while at higher concentrations only the sub-linear term is present. These results imply that the NFL behavior could be a new state of matter in its own right rather than a consequence of the underlying QPT. [Preview Abstract] |
Tuesday, March 19, 2013 8:48AM - 9:00AM |
F19.00005: Superfluid density in heavy fermion superconductor Ce$_{1-x}$Yb$_x$CoIn$_5$ Lei Shu, D.E. MacLaughlin, O.O. Bernal, X.P. Shen, S. Pham, I. Lum, M.B. Maple Recent x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements on the superconducting heavy fermion system Ce$_{1-x}$Yb$_x$CoIn$_5$ reveal that the correlated electron state is stabilized throughout the range $0 < x < 0.8$, apparently due to cooperative behavior of Ce and Yb ions involving their unstable valences. Phase separation occurs for $x > 0.8$. Interestingly, the superconducting critical temperature decreases linearly with $x$ from 2.3 K at $x = 0$ towards 0 K at $x = 1$. Transverse-field muon spin rotation experiments have been performed on Ce$_{1-x}$Yb$_x$CoIn$_5$ alloys. Based on these measurements, we report the absolute value of magnetic penetration depth as a function of $x$ and discuss whether $T_c$ is controlled by the superfluid density of superconducting carriers. The results are compared to a recently proposed theory for the superconductivity in Ce$_{1-x}$Yb$_x$CoIn$_5$ [Preview Abstract] |
Tuesday, March 19, 2013 9:00AM - 9:12AM |
F19.00006: Anomalous upper critical field in CeCoIn$_5$/YbCoIn$_5$ superlattices with a Rashba-type heavy fermion interface Masaaki Shimozawa, S.K. Goh, Y. Mizukami, H. Shishido, D. Watanabe, S. Yasumoto, M. Yamashita, T. Terashima, Y. Yanase, T. Shibauch, A.I. Buzdin, Y. Matsuda We report the precise angular dependence of the upper critical field ($H_{\mathrm{c2}})$ in the epitaxial superlattices CeCoIn$_5(n)$/YbCoIn$_5$(5), formed by alternating layers of $n$ and 5 unit-cells thick CeCoIn$_5$ with a strong Pauli effect and normal metal YbCoIn$_5$, respectively [1]. For the $n =$ 3 superlattice, $H_{\mathrm{c2}}(\theta )$ changes smoothly as a function of the field angle $\theta $. However, near the superconducting transition temperature,$ H_{\mathrm{c2}}(\theta )$ shows a cusp near the angle parallel to the plane of the superlattice. This cusp behavior disappears for $n =$ 4 and 5. This sudden disappearance suggests the relative dominance of the orbital depairing effect in the $n =$ 3 superlattice, which may be due to the suppression of the Pauli effect in a system with local inversion symmetry breaking [2].\\[4pt] [1] Y. Mizukami \textit{et al.}, Nature Phys. \textbf{7,} 849 (2011).\\[0pt] [2] S. K. Goh \textit{et al.}, Phys. Rev. Lett. \textbf{109,} 157006 (2012). [Preview Abstract] |
Tuesday, March 19, 2013 9:12AM - 9:24AM |
F19.00007: Strong pressure dependence of the magnetic penetration depth in single crystals of the heavy fermion system CeCoIn$_5$ studied by muon spin rotation Ludovic Howald, Alexander Maisuradze, Pierre Dalmas de R\'eotier, Alain Yaouanc, Christopher Baines, Gerard Lapertot, Karine Mony, Jean-pascal Brison, Hugo Keller The pressure dependence ($0-1$ GPa) of the in-plane magnetic penetration depth ($\lambda_a$), the penetration depth anisotropy ($\gamma=\lambda_c/\lambda_a$) and the temperature dependence of $1/\lambda^2_i$ ($i=a,c$) were studied in single crystals of the heavy fermion system CeCoIn$_5$ by means of muon spin rotation. A strong decrease of $\lambda_a$ with pressure was observed, while $\gamma$ and $\lambda_i^2(0)/\lambda_i^2(T)$ are pressure independent. A linear relationship between $1/\lambda_a^2$(270 mK) and Tc was also found. The large decrease of $\lambda_a$ with pressure is the signature of an increase of the number of superconducting quasiparticles by a factor of about 2. [Preview Abstract] |
Tuesday, March 19, 2013 9:24AM - 9:36AM |
F19.00008: STM Spectroscopic Mapping of Quasiparticle States in the Superconducting State of CeCoIn$_5$ Shashank Misra, Brian Zhou, Eduardo H. da Silva Neto, Pegor Aynajian, Ryan Baumbach, J.D. Thompson, Eric Bauer, Ali Yazdani The heavy fermion compounds provide an interesting playground to study strongly correlated physics, as a variety of unusual low-temperature states emerge in relatively close proximity to one another in their phase diagrams. However, to date, very little spectroscopic information about these low-temperature phases, including unconventional superconductivity, is known. Recently, at comparatively high temperatures, Aynajian and coworkers\footnote{P. Aynajian, {\it et al.}, {\it Nature} {\bf 486}, 201-206 (2012).} used scanning tunneling microscopy (STM) to visualize the formation of heavy quasiparticles in one of the prototype 115 compounds, CeCoIn$\mathrm{_5}$. Here, we use a new home-built STM to extend the spatial mapping of the electronic states of CeCoIn$_5$ down to its superconducting state at mK temperatures. This work was supported by the DOE and NSF. [Preview Abstract] |
Tuesday, March 19, 2013 9:36AM - 9:48AM |
F19.00009: STM Spectroscopic Mapping of Quasi-Particle States in the Vortex State of CeCoIn$_5$ Brian Zhou, Shashank Misra, Pegor Aynajian, Eduardo da Silva Neto, Ryan Baumbach, J.D. Thompson, Eric Bauer, Ali Yazdani The superconducting properties of the heavy-fermion CeCoIn$_5$ emerge from a remarkable backdrop of strong electron correlation and magnetic criticality. Fittingly, this superconducting phase is itself remarkable, displaying signatures of unconventional pairing with (d-wave) line nodes in the order parameter and a Pauli-limited upper critical field below 700 mK [1]. Through scanning tunneling microscopy at milli-kelvin temperatures, we present, for the first time, atomically-resolved spectroscopy of CeCoIn$_5$ as the application of a magnetic field weakens and eventually destroys superconductivity.\\[4pt][1] J. D. Thompson and Z. Fisk, J. Phys. Soc. Jpn. \textbf{81}, 011002 (2012). [Preview Abstract] |
Tuesday, March 19, 2013 9:48AM - 10:00AM |
F19.00010: Long range order and two-fluid behavior in heavy electron materials Nicholas Curro, Abigail Shockley, Kent Shirer, Adam Dioguardi, Nicholas abRoberts-Warren, John Crocker, Ching Lin, David Nisson The heavy electron Kondo liquid is an emergent state of condensed matter that displays universal behavior independent of material details. Properties of the heavy electron liquid are best probed by NMR Knight shift measurements, which provide a direct measure of the behavior of the heavy electron liquid that emerges below the Kondo lattice coherence temperature as the lattice of local moments hybridizes with the background conduction electrons. Because the transfer of spectral weight between the localized and itinerant electronic degrees of freedom is gradual, the Kondo liquid typically coexists with the local moment component until the material orders at low temperatures. The two-fluid formula captures this behavior in a broad range of materials in the paramagnetic state. In order to investigate two-fluid behavior and the onset and physical origin of different long range ordered ground states in heavy electron materials, we have extended Knight shift measurements to URu$_2$Si$_2$, CeIrIn$_5$ and CeRhIn$_5$. Our results indicate that the ordered state can emerge from either the Kondo liquid or heavy electron component, and imply that the nature of the ground state is strongly coupled with the hybridization in the Kondo lattice. [Preview Abstract] |
Tuesday, March 19, 2013 10:00AM - 10:12AM |
F19.00011: Study of the Kondo lattice on La doped CeCoIn$_5$ G. Koutroulakis, H. Yasuoka, T. Zhou, S. E. Brown, E. D. Bauer, J. D. Thompson The effect of non-magnetic impurities on the properties of the Kondo lattice was investigated through nuclear magnetic/quadrupolar resonance (NMR/NQR) experiments on Ce$_{1-x}$La$_x$CoIn$_5$. Specifically, comprehensive $^{115}$In, $^{139}$La NQR and NMR measurements were carried out on single crystals of various La concentration levels (x=0, 2, 3, and 5\%) for temperatures 1.5K-80K and applied magnetic field values 0T-7T. Our results indicate that the ramifications of the Kondo-ion substitution extend well-beyond the vicinity of the particular site, readily affecting the heavy-fermion forming hybridization. It is suggested that the spin polarization around La impurities is modulated on a much larger length scale than that of charge oscillations. [Preview Abstract] |
Tuesday, March 19, 2013 10:12AM - 10:24AM |
F19.00012: High Field Knight Shift studies in CeIrIn5 Abigail Shockley, Nicholas apRoberts-Warren, David Nisson, Phil Kuhns, Arneil Reyes, Peter Klavins, Nicholas Curro All heavy fermion compounds that have been measured with NMR exhibit a Knight shift anomaly, in which the Knight shift does not scale with the bulk susceptibility below a characteristic temperature, T*.~ Typically this temperature corresponds with the Kondo lattice coherence temperature as measured by other probes.~ In order to investigate the microscopic origin of this anomaly, we have conducted high field measurements of the In-115 Knight shift in CeIrIn5 up to 30 T.~ We find that although the onset temperature T* is field independent, the overall low temperature shift below T* is suppressed.~ In the context of the two-fluid model, these results suggest that that the dominant change is in the local moment channel. [Preview Abstract] |
Tuesday, March 19, 2013 10:24AM - 10:36AM |
F19.00013: Probing the hybridization gap in heavy fermions by temperature dependent ARPES Cris Adriano, Fanny Rodolakis, Priscila Rosa, Francisco Restrepo, Dimitar Tenev, Mucio Continentino, Zachary Fisk, Juan Carlos Campuzano, Pascoal Pagliuso We report temperature dependent angle-resolved photoemission spectroscopy (ARPES) for pure and Cd-doped Ce$_{2}$RhIn$_{8}$ heavy fermion compounds. Our results reveal that for Ce$_{2}$RhIn$_{8}$ at T $=$ 100 K once the $f $-- conduction electrons magnetic scattering becomes larger than the phonon scattering, even states of different parities can hybridize, forming many-body quasiparticles with heavy masses. We further show that at a temperature of 20 K, where the hybridization of conduction electrons and $f $states is stronger, a spectral gap is observable in the ARPES spectra. Interestingly, when replacing In by Cd to tune the local density of conduction electrons states at the Ce$^{3+}$ site, we find a strong reduction of the $f$ - conduction electrons hybridization strength, and the suppression of the hybridization gap at low temperatures. We also observe that the $f $states near the chemical potential hybridize mostly with out-of-plane $p$ states (presumably from In). These findings have important consequences for the understanding of the different antiferromagnetic and exotic superconducting ground states that occur in these families of materials. [Preview Abstract] |
Tuesday, March 19, 2013 10:36AM - 10:48AM |
F19.00014: Fermi Surface evolution as a function of temperature in heavy fermion Ce$_{2}$RhIn$_{8}$ probed by ARPES Fanny Rodolakis, Cris Adriano, Francisco Restrepo, Dimitar Tenev, Pascoal Pagliuso, Juan Carlos Campuzano The crossover of 4$f$ localized magnetic moments at high temperatures into itinerant states of heavy mass at low temperatures in Cerium-based heavy fermion materials is a fundamental problem in condensed matter physics, involving a temperature-dependent hybridization between the $f$ levels immersed in a sea of conduction electrons (\textit{ce}). Due to the Luttinger theorem, this hybridization leads to a Fermi surface (FS) enlargement at low temperature: as the $f$ electrons become itinerant, their contribution to E$_{\mathrm{F}}$ increases. We have studied the evolution of the heavy fermion FS in Ce2RhIn8 as a function of temperature using angle resolved photoemission. We observed topological changes that emerge at a temperature scale much higher than the onset of the coherence character of the $f$ electrons. This behavior can be related to the evolution of the electrical resistivity as a function of temperature: as typically found for Kondo lattice materials, it first decreases when temperature is lowered, but increases below $\sim $ 150K as the magnetic scattering of the \textit{ce} by the localized $f$ electrons becomes larger than the phonon scattering. It reaches a maximum and then drops when the magnetic scattering becomes coherent for T$^{\ast} \sim $ 5K. This multiple scale behavior of the $f$ electrons is in good agreement with a recent theoretical study performed in the parent compound CeRhIn$_{5}$ [1].\\[4pt] [1] Choi et al, Phys. Rev. Lett. \textbf{108}, 016402. [Preview Abstract] |
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