Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session L23: Interplay of Magnetism, Superconductivity and Unconventional Order in Heavy Fermion MaterialsInvited
|
Hide Abstracts |
Sponsoring Units: GMAG Chair: Pengcheng Dai, pdai.utk@gmail.com Room: New Orleans Theater B |
Wednesday, March 15, 2017 11:15AM - 11:51AM |
L23.00001: The spin resonance of CeCoIn$_{\mathrm{5}}$: A dynamical precursor of the Q-Phase Invited Speaker: STEPHANE RAYMOND The concept of soft mode is central to condensed matter physics; it emphasizes the relationship between the excitation spectrum and the ground state of different phases of matter in a variety of situation ranging from lattice dynamical instability in ferroelectrics to Bose-Einstein condensation of magnons in magnetic insulators. Unconventional superconductivity often occurs on the verge of magnetic ordering or charge density-wave formation asking the question whether these states of matter are competitive or collaborative phases. Unconventional superconductivity modifies the magnetic excitation spectrum of a metal by a feedback effect corresponding to the apparition of a new collective mode, the spin resonance. It was recently shown by detailed inelastic neutron scattering experiments performed on the model $d$-wave unconventional superconductor CeCoIn$_{\mathrm{5}}$ that the spin resonance mode has the same symmetry [1] as the adjacent field induced magnetic ordered phase, the Q-phase [2]. This fact, together with the known softening of the dynamical mode under applied magnetic field [3,4], strongly supports a scenario where the static magnetic order is realized by a condensation of the superconducting spin resonance. [1] S. Raymond and G. Lapertot, Phys. Rev. Lett. 115, 037001 (2015). [2] M. Kenzelmann et al., Science, 321, 1652 (2008). [3] C. Stock et al., Phys. Rev. Lett. 109, 167207 (2012). [4] S. Raymond et al., Phys. Rev. Lett. 109, 237210 (2012). [Preview Abstract] |
Wednesday, March 15, 2017 11:51AM - 12:27PM |
L23.00002: Spin excitations in superconducting CeCoIn5 and antiferromagnetic CeRhIn5 -- From doublet spin resonance to quasiparticle breakdown Invited Speaker: Chris Stock The 115 series of compounds provides a unique opportunity to study unconventional d-wave superconductivity in the clean limit. In this talk we will compare the spin excitations in superconducting CeCoIn5 to that in antiferromagnetic and helically ordered CeRhIn5. In CeCoIn5, we will show that superconductivity is accompanied by a sharp spin resonance. High resolution neutron scattering finds that this resonance mode is a doublet and is suggestive that it is the soft mode for density wave order at high fields termed the Q-phase [1,2]. The results in CeCoIn5 are strikingly different to that observed in antiferromagnetic CeRhIn5 [3,4]. This system displays both sharp magnon excitations, however also a strong continuum of excitations originating from a coupling between itinerant and localized responses. This observation of two distinct components illustrates the dual nature of the spins in CeRhIn5 [5] and the nature of the parent phase from which unconventional superconductivity derives from. [1] C. Stock\textit{ et al}. Phys. Rev. let. \textbf{10}0, 087001 (2008) [2] C. Stock\textit{ et al}. Phys. Rev. Lett.\textbf{ 109}, 167207 (2012). [3] M. Kenzelmann \textit{et. al}. Science 321, 1652 (2008); C. Stock\textit{ et al}. Phys. Rev. Lett.\textbf{ 114}, 247005 (2015); S. Raymond and G. Lapertot Phys. Rev. Lett.\textbf{ 115}, 037001 (2015). [4] P. Das\textit{ et al}. Phys. Rev. Lett.\textbf{ 113}, 246403 (2014). [5] T. Park \textit{et al.} Proc. Natl. Acad. Sci. U.S.A.\textbf{ 105}, 6825 (2008). [Preview Abstract] |
Wednesday, March 15, 2017 12:27PM - 1:03PM |
L23.00003: Magnetism, Criticality and Superconductivity in Heavy-Fermion Compounds Invited Speaker: J. D. Thompson Unraveling the interrelationship among magnetism, quantum criticality and unconventional superconductivity is a challenge that cuts across families of correlated electron materials, ranging from cuprate, iron-pnictide, and organic to heavy-fermion systems. Among these families, heavy-fermion compounds have served as prototypes of the interdependence, and among the heavy-fermion systems, the so-called Ce115s (CeMIn$_{\mathrm{5}}$, M$=$Co, Rh, Ir) have been particularly instructive. The study of these and related Ce-based heavy-fermion materials has shown us clearly where to look for new unconventional superconductors -- at a zero-temperature magnetic/non-magnetic boundary. In some examples, such as CeRhIn$_{\mathrm{5}}$ and its derivatives, the quantum-critical state at this boundary can be unconventional, involving both fluctuations of a symmetry-breaking order parameter and a qualitative reconstruction of electronic states. Irrespective of whether the criticality is conventional or unconventional, the unconventional superconductivity that develops in its proximity also can be unstable toward the formation of magnetic order, presumably due to partial condensation of magnetic excitations at gap nodes. It seems possible that similar exotic states should appear in other strongly correlated electron systems. In collaboration with Y. K. Luo, D. Y. Kim, R. Movshovich, F. Ronning, P. F. S. Rosa, Q. Si and E. D. Bauer. [Preview Abstract] |
Wednesday, March 15, 2017 1:03PM - 1:39PM |
L23.00004: Topological nodal superconductivity in the heavy fermion metal UPt3 Invited Speaker: Andriy Nevidomskyy The concept of topological states of matter has captured the imagination of physicists in the last decade. Traditionally, such topological phases are predicted to occur in fully gapped insulating or superconducting materials and are characterized by topologically protected gapless excitations on the surface [1]. Recently, it has been realized that such protected surface states may also exist in certain classes of metallic materials with gapless bulk excitations. Here, I will demonstrate the application of this concept, focusing in particular on the low-temperature B-phase of the heavy fermion superconductor UPt$_3$. Josephson interferometry measurements provide strong evidence for the triplet, chiral pairing symmetry in UPt$_3$, which endow the Cooper pairs with orbital angular momentum $L_z =\pm 2$ along the $c$-axis [2]. Such pairing supports both line and point nodes in the superconducting gap, and we show that both types of nodal quasiparticles possess nontrivial topology in the momentum space. In particular, the point nodes located at the intersections of the closed Fermi surfaces with the $c$-axis act as the double monopoles and anti-monopoles of the Berry curvature [3]. Consequently, we predict that the B phase of UPt$_3$ should support an anomalous thermal Hall effect, various magneto-electric effects such as the polar Kerr effect, in addition to the topologically protected Majorana Fermi arcs on the (1,0,0) and (0,1,0) surfaces [3]. At the transition from the B-phase to the A-phase upon increasing temperature, the time reversal symmetry is restored, and the surface Fermi arcs disappear. The effect of quenched disorder on the topologically non-trivial B-phase will also be discussed.\vspace{3mm} \\ References:\\ {[1]} M. Z. Hasan and C. L. Kane, "Colloquium: Topological insulators," Rev. Mod. Phys. 82, 3045 (2010).\\ {[2]} J. D. Strand, D. J. Van Harlingen, J. B. Kycia, and W. P. Halperin, "Evidence for complex superconducting order parameter symmetry in the low-temperature phase of UPt$_3$ from Josephson interferometry", Phys. Rev. Lett. 103, 197002 (2009).\\ {[3]} P. Goswami and A. H. Nevidomskyy "Topological Weyl superconductor to diffusive thermal Hall metal crossover in the B-phase of UPt$_3$", Phys. Rev. B 92, 214504 (2015). [Preview Abstract] |
Wednesday, March 15, 2017 1:39PM - 2:15PM |
L23.00005: Hybridization with a twist: Hidden (hastatic) order in URu$_2$Si$_2$ Invited Speaker: Rebecca Flint The hidden order developing below 17.5K in the heavy fermion material URu$_2$Si$_2$ has eluded identification for over thirty years [1]. A number of recent experiments have shed new light on the nature of this phase. In particular, de Haas-van Alphen measurements indicate nearly perfectly Ising quasiparticles deep in the hidden order phase [2], and recent nonlinear susceptibility measurements show that this strong Ising anisotropy persists up to and above the hidden order transition itself [3,4]. Along with other features, this Ising anisotropy implies that the conduction electrons hybridize with a local Ising moment - a 5f$^2$ state of the uranium atom with integer spin. As the hybridization mixes states of integer and half-integer spin, it is itself a spinor and this ``hastatic'' (hasta: [Latin] spear) order parameter therefore breaks both time-reversal and double time-reversal symmetries [5,6]. A microscopic theory of hastatic order naturally unites a number of disparate experimental results from the large entropy of condensation to the spin rotational symmetry breaking seen in torque magnetometry, and provides a number of experimental predictions. Moreover, this new spinorial order parameter provides a window into a number of new heavy fermion phases. [1] J. Mydosh and P. M. Oppeneer, RMP 83, 1301 (2011) [2] M. M. Altarawneh, N. Harrison, S. E. Sebastian, L. Balicas, P. H. Tobash, J. D. Thompson, F. Ronning, and E. D. Bauer, PRL 106, 146403 (2011) [3] J. Trinh, E. Bruck, T. Siegrist, R. Flint, P. Chandra, P. Coleman and A. P. Ramirez, arXiv:1608.07009 (2016) [4]R. Flint, P. Chandra and P. Coleman PRB 86, 155155 (2012) [5] P. Chandra, P. Coleman and R. Flint, Nature 493, 611 (2013) [6] P. Chandra, P. Coleman and R. Flint, PRB 91, 205103 (2015) [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