Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session D41: Hidden Order and Quantum Criticality in Heavy Fermions |
Hide Abstracts |
Sponsoring Units: DMP DCMP Chair: Johnpierre Paglione, University of Maryland Room: 413 |
Monday, March 16, 2009 2:30PM - 2:42PM |
D41.00001: Incommensurate spin resonance in URu2Si2. Jian Xin Zhu, Alexander Balatsky, Athanasios Chantis, Hari Dahal, David Parker The nature of the hidden order (HO) in URu2Si2 below T$_{HO}$ = 17.5K has been a puzzle for a long time. Here we propose to search for the spin resonance as a tool to elucidate the nature of the HO. We consider inelastic neutron scattering in URu2Si2 and argue that a gap in the fermion spectrum will produce an incommensurate spin resonance at Q* = (1$\backslash $pm 0.4, 0,0) at $\omega _{res}$ = 4-6 meV. We assume that the HO gap is due to a particle-hole condensate that connects nested parts of the Fermi surface with nesting vector {\$}Q\^{}* . The predicted behavior of the spin susceptibility is strikingly similar to the phenomenology of resonance peaks in high-T{\_}c and heavy fermion superconductors. The energy of the resonance peak scales with T$_{HO}$ $\omega _{res} \quad \sim $ 4 k{\_}BT$_{HO}$ [Preview Abstract] |
Monday, March 16, 2009 2:42PM - 2:54PM |
D41.00002: Thermodynamical Properties across Quantum Critical Points Jianda Wu, Lijun Zhu, Qimiao Si Quantum critical points (QCPs) are of extensive current interest, in part because they strongly influence the physical properties at finite temperatures. Thermodynamic properties have recently been used as a means to probe the energy scales in the quantum critical heavy fermion metals [1]. In addition, the divergence of the Gruneisen ratio (thermal expansion to specific heat) or its magnetic analog at any QCP, theoretically predicted a few years ago [2], has been observed in a growing list of quantum critical materials. In this work, we study the entropy as a function of control parameter in several theoretical models for quantum criticality. We explicitly demonstrate that the entropy is maximized near the QCP, which is compatible with the divergence of the Gruneisen ratio exactly at the QCP. When the control parameter is a magnetic field, we also study the field dependence of the isothermal magnetization and other magneto-thermal properties. [1] P. Gegenwart et al, Science 315, 969 (2007); [2] L. Zhu et al, PRL 91, 066404 (2003). [Preview Abstract] |
Monday, March 16, 2009 2:54PM - 3:06PM |
D41.00003: Cyclotron Resonance in the Hidden-Order Phase of Ultraclean URu$_2$Si$_2$ Single Crystals T. Shibauchi, K. Hashimoto, K. Ikada, S. Tonegawa, H. Shishido, Y. Haga, T. D. Matsuda, Y. Onuki, H. Yamagami, Y. Matsuda In the heavy fermion compound URu$_2$Si$_2$, the hidden-order transition occurs at 17.5 K, whose origin is still an enigma. Of primary importance is elucidating the electronic structure of the hidden-order phase. Here we report the first observation of cyclotron resonance in the ultraclean crystals of URu$_2$Si$_2$ with residual resistivity ratio $RRR=670$. The magnetic-field dependence of the microwave surface impedance in the Azbel'-Kerner geometry shows clear cyclotron resonance lines whose line width has characteristic temperature dependence consistent with the transport measurements. In addition to the bands which have been previously identified in the quantum oscillation measurements, we newly find the missing band with the heaviest mass, which can account for the large specific heat coefficient in the hidden-order phase of URu$_2$Si$_2$. [Preview Abstract] |
Monday, March 16, 2009 3:06PM - 3:18PM |
D41.00004: Reconstruction of the Fermi Surface Deep inside the Hidden-Order Phase of Very Clean URu$_2$Si$_2$ Y. Matsuda, H. Shishido, T. Shibauchi, K. Hashimoto, Y. Haga, T.D. Matsuda, Y. Onuki, T. Sasaki, T. Oizumi, N. Kobayashi, T. Takamasu, K. Takehana, Y. Imanaka The nature of the hidden order (HO) phase in URu$_2$Si$_2$ is a long standing mystery in heavy-fermion physics. It has been shown that the HO phase is destroyed at $H_0$=36~T ($T=0$) and several new phases appear above $H_0$. Here we studied the low temperature/high field phase of very clean URu$_2$Si$_2$ single crystals ($RRR$=670) by the transport properties. We find that the Hall resistivity jumps at $H_h$=22~T well inside the HO phase and new quantum oscillations appear at high fields starting slightly below $H_h$. These results indicate a reconstruction of the Fermi surface and a possible phase transition well inside the HO phase. The present results provide strong evidence that the HO transition is described by an itinerant rather than a localized electron picture. [Preview Abstract] |
Monday, March 16, 2009 3:18PM - 3:30PM |
D41.00005: Probing the Hidden Order in URu$_2$Si$_2$ by Impurity Doping Seung-Ho Baek, Nicholas Curro, M. Graf, A. Balatsky, Eric Bauer, Jason Cooley, Jim Smith URu$_2$Si$_2$ exhibits a clear broken symmetry ground state at 17.5 K, but the nature of the order parameter has not been known for more than two decades. Motivated by the fact that Rh doping in this compound induces antiferromagnetism, indicating that the hidden order is closely related with the antiferromagnetism, we studied $^{29}$Si NMR with varying Rh concentration. This $^{29}$Si NMR study reveals that the antiferromagnetism arises from the local suppression of the hidden order by Rh doping. We propose that the antiferromagnetism emerges as a result of the local suppression of the hidden order yet only within the long range hidden order phase. [Preview Abstract] |
Monday, March 16, 2009 3:30PM - 3:42PM |
D41.00006: Electronic structure model of the hidden order and Fermi surface gapping in URu$_{2}$Si$_{2}$ Peter Oppeneer, Saad Elgazzar, Jan Rusz, Michi-To Suzuki, John Mydosh The hidden order (HO) in the heavy-fermion superconductor URu$_{2}$Si$_{2}$ has been studied for more than 20 years, without that the nature of this unusual phase could be uncovered. We present a microscopic explanation for the mechanism of the hidden order, on the basis of state-of-the-art electronic structure calculations. In particular, we show that our calculations explain very well all the known properties of the paramagnetic and large moment antiferromagnetic (LMAF) phases. Exploiting the known experimental equivalence between the Fermi surface properties of the LMAF and HO phases, we identify the Fermi surface ``hot spots'' where a Fermi surface instability is lifted through spontaneous symmetry breaking, causing a surprisingly large Fermi surface gapping. We quantify that symmetry breaking through collective modes of antiferromagnetic moment excitations can induce a substantial Fermi surface gapping that consistently explains the transport properties and entropy loss of the HO phase. [Preview Abstract] |
Monday, March 16, 2009 3:42PM - 3:54PM |
D41.00007: Heavy Fermion and non-Fermi Liquid Properties vs Size: From the Micro to the Nano G.R. Stewart, J.S. Kim, K. Samwer Y. Y. Chen et al. have studied nanoparticles of several systems, including CePt$_{2}$ [1]. We report here the specific heat, C, down to 0.05 K and $\chi$ to 2 K as a function of size for several Ce- and U-heavy Fermion and non-Fermi liquid (nFl) systems, including UBe$_{13}$ and Rh-doped CeRu$_{2}$Si$_{2}$. Using dry sieves (for larger particles) and aqueous suspension/filtration techniques using Isopore$^{TM}$ filters (for smaller particles), size gradations from 45-53 $\mu$ (essentially bulk) down to 0.6-1.2 $\mu$ were studied. One goal was to study the evolution of nFl behavior vs decreasing size at a Quantum Critical Point, where the spatial extent of the fluctuations should become infinite, or at least larger than the particle at some size. Ce-systems showed the beginning of Kondo peak behavior in C below 3 $\mu$, however it was still possible to determine the evolution of the intrinsic low temperature nFl C/T $\sim$ logT in Rh-doped CeRu$_{2}$Si$_{2}$ as a function of decreasing size to address this goal. The effect of size on superconductivity and m$^{*}$ in UBe$_{13}$ will also be discussed.\\[0pt] [1] Y. Y. Chen et al., Phys. Rev. Lett. 98, 157206 (2007). [Preview Abstract] |
Monday, March 16, 2009 3:54PM - 4:06PM |
D41.00008: Quantum criticality in the Bose-Fermi Kondo model and the quantum-to-classical mapping Stefan Kirchner, Qimiao Si The Bose-Fermi Kondo model (BFKM) occurs as the effective quantum impurity model within the Extended Dynamical Mean Field Theory (EDMFT) for quantum critical heavy fermion metals. The quantum critical point (QCP) of the BFK is therefore related to the one in the Kondo lattice model, the relevant low-energy model for heavy fermion compounds. There have been indications that the QCP of the BFKM cannot be described in terms of a local O(3)-symmetric $\phi^4$-theory as predicted by the quantum-to-classical mapping, but the issue remains to be settled. In this work we demonstrate that the quantum-to-classical mapping for the spin-isotropic SU(N) BFKM breaks down in a large N limit[1]. We also show that this feature is associated with the Berry phase term of the spin path integral and therefore persists for finite N [2]. We analyzse the influence of this breakdown on the dynamic scaling properties of the Kondo lattice obtained through the EDMFT, and also discuss the connection of our results with those of the Ising-anisotropic BFKM. [1] L. Zhu, S. Kirchner, Q. Si and A. Georges, PRL 93, 267201 (2004). [2] S. Kirchner and Q. Si, arXiv:0808.2647 (2008). [Preview Abstract] |
Monday, March 16, 2009 4:06PM - 4:18PM |
D41.00009: Thermal expansion and magnetostriction of the heavy fermion antiferromagnet YbAgGe G.M. Schmiedeshoff, A.W. Lounsbury, S.J. Tracy, S.L. Bud'ko, P.C. Canfield YbAgGe is a stoichiometric heavy fermion compound that exhibits antiferromagnetic order and field induced quantum criticality.~ We will discuss this behavior, and present a unified phase diagram of this compound in the T-H plane, in light of our recent thermal expansion and magnetostriction measurements.~ We find a remarkable agreement between thermodynamic, transport and microscopic measurements on this model system. Work at Occidental College was supported by the National Science Foundation under DMR-0704406. Work at the Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-07CH11358. [Preview Abstract] |
Monday, March 16, 2009 4:18PM - 4:30PM |
D41.00010: Magnetic-field-dependence of the YbRh$_2$Si$_2$ Fermi surface Patrick Rourke, Alix McCollam, Gerard Lapertot, Georg Knebel, Jacques Flouquet, Stephen Julian Magnetic-field-induced changes of the Fermi surface play a central role in theories of the exotic quantum criticality of YbRh$_2$Si$_2$. We have carried out de Haas--van Alphen measurements in the magnetic field range 8 T~$\leq H \leq$~16~T, and directly observe field-dependence of the extremal Fermi surface areas. Our data support the theory that a low-field ``large'' Fermi surface, including the Yb 4$f$ quasi-hole, is increasingly spin-split until a majority-spin branch undergoes a Lifshitz transition and disappears at $H_0 \approx 10$~T, without requiring 4$f$-localization at $H_0$. [Preview Abstract] |
Monday, March 16, 2009 4:30PM - 4:42PM |
D41.00011: Electron Spin Resonance in a Kondo lattice, Pedro Schlottmann Until recently it was commonly believed that due to the broad linewidth electron spin resonance (ESR) could not be observed in heavy-fermion compounds. This was proven to be wrong, since an ESR signal was found$^1$ in single crystals of YbRh$_2$Si$_2$ as well as in other systems. Recently, Abrahams and W\"olfle$^2$ studied the ESR signal of a heavy fermion band within the framework of the Anderson lattice. They obtained that the heavy mass in conjunction with ferromagnetic fluctuations can lead to narrow resonances, and concluded that the observed ESR in YbRh$_2$Si$_2$ is due to the heavy fermion conduction states and not the Yb localized moments. Here I study the ESR linewidth for localized moments within the framework of the Kondo lattice model. An ESR signal can only be observed if the Kondo temperature is sufficiently small. In addition, to obtain an observable signal short-range ferromagnetic correlations between the localized spins are necessary, which may lead to a bottleneck situation, that narrows the linewidth. It is concluded that from ESR data alone it is not possible to distinguish if the resonance is due to localized spins or conducting heavy electron spins. \par\noindent Work supported by the Department of Energy under grant No. DE-FG02-98ER45797. \par\noindent $^1$ J. Sichelschmidt {\it et al.}, Phys. Rev. Lett. {\bf 91}, 156401 (2003). \par\noindent $^2$ E. Abrahams and P. W\"olfle, Phys. Rev. B {\bf 78}, 104423 (2008). [Preview Abstract] |
Monday, March 16, 2009 4:42PM - 4:54PM |
D41.00012: Cyrstal Synthesis of Novel Yb-Pt-Pb Phases Carlos Marques, Yuri Janssen, Marcus Bennet, Moo Sung Kim, Keeseong Park, Peter Khalifah, Meigan Aronson We have used flux techniques to explore the Yb-Pt-Pb ternary phase diagram, and have grown a number of intermetallic compounds including YbPt, Yb$_{3}$Pt$_{5}$, and the new~Yb$_{5}$Pt$_{9}$, YbPt$_{2}$, Yb$_{3}$Pt$_{4}$ and Yb$_{2}$Pt$_{2}$Pb, as well as Yb$_{3}$Pt$_{5}$Si and YbPtSi. The crystal structure of these different compounds will be compared. A particular focus has been the synthesis of single crystals of quantum critical antiferromagnet (AF) Yb$_{3}$Pt$_{4}$, and we show that it is possible to~synthesize crystals which are large enough for neutron diffraction measurements. Laue patterns and neutron rocking curves along with other methods show that these cyrstals are of very high quality. Initial results of neutron diffraction and inelastic scattering experiments on single Yb$_{3}$Pt$_{4}$ crystals and arrays of multiple Yb$_{3}$Pt$_{4}$ crystals will be presented. [Preview Abstract] |
Monday, March 16, 2009 4:54PM - 5:06PM |
D41.00013: Neutron scattering studies on Yb$_{3}$Pt$_{4}$ Y. Janssen, M.C. Bennett, C. Marques, L. Wu, M.S. Kim, K.S. Park, Q. Huang, J.Y. Li, Y. Chen, J.W. Lynn, M.C. Aronson The antiferromagnetic (AF) intermetallic compound Yb$_{3}$Pt$_{4}$ shows a magnetic phase diagram which includes a quantum critical point, but is different from other Yb-containing quantum critical compounds. We elucidated the zero-field behavior by neutron scattering on both polycrystal and single-crystal samples. The magnetic structure due to the single-site-low-symmetry Yb moments was determined by diffraction. The AF unit cell coincides with the crystallographic unit cell, and shows pairs of Yb nearest-neighbor moments pointing directly towards each other. The order parameter is consistent with a continuous transition at the N\'{e}el temperature (2.4 K) and can be described by a simple mean-field model. The ordered moment amounts to $\sim $ 1.2 $\mu _{B}$/Yb at 0 K. Inelastic neutron scattering reveals that the crystal electric field lifts the degeneracy of the Yb 4f ground state into 4 doublets, consistent with specific heat results. [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