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Fabbris G, Meyers D, Shen Y, Bisogni V, Zhang J, Mitchell JF, Norman MR, Johnston S, Feng J, Chiuzbăian GS, Nicolaou A, Jaouen N, Dean MPM. Resonant inelastic x-ray scattering data for Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates. Sci Data 2023; 10:174. [PMID: 36991033 PMCID: PMC10060392 DOI: 10.1038/s41597-023-02079-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 03/16/2023] [Indexed: 03/31/2023] Open
Abstract
Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates are intriguing candidates for mimicking the properties of high-temperature superconducting cuprates. The degree of similarity between these nickelates and cuprates has been the subject of considerable debate. Resonant inelastic x-ray scattering (RIXS) has played an important role in exploring their electronic and magnetic excitations, but these efforts have been stymied by inconsistencies between different samples and the lack of publicly available data for detailed comparison. To address this issue, we present open RIXS data on La4Ni3O10 and La4Ni3O8.
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Lin JQ, Villar Arribi P, Fabbris G, Botana AS, Meyers D, Miao H, Shen Y, Mazzone DG, Feng J, Chiuzbăian SG, Nag A, Walters AC, García-Fernández M, Zhou KJ, Pelliciari J, Jarrige I, Freeland JW, Zhang J, Mitchell JF, Bisogni V, Liu X, Norman MR, Dean MPM. Strong Superexchange in a d^{9-δ} Nickelate Revealed by Resonant Inelastic X-Ray Scattering. PHYSICAL REVIEW LETTERS 2021; 126:087001. [PMID: 33709756 DOI: 10.1103/physrevlett.126.087001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 01/15/2021] [Indexed: 06/12/2023]
Abstract
The discovery of superconductivity in a d^{9-δ} nickelate has inspired disparate theoretical perspectives regarding the essential physics of this class of materials. A key issue is the magnitude of the magnetic superexchange, which relates to whether cuprate-like high-temperature nickelate superconductivity could be realized. We address this question using Ni L-edge and O K-edge spectroscopy of the reduced d^{9-1/3} trilayer nickelates R_{4}Ni_{3}O_{8} (where R=La, Pr) and associated theoretical modeling. A magnon energy scale of ∼80 meV resulting from a nearest-neighbor magnetic exchange of J=69(4) meV is observed, proving that d^{9-δ} nickelates can host a large superexchange. This value, along with that of the Ni-O hybridization estimated from our O K-edge data, implies that trilayer nickelates represent an intermediate case between the infinite-layer nickelates and the cuprates. Layered nickelates thus provide a route to testing the relevance of superexchange to nickelate superconductivity.
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Zhang J, Phelan D, Botana AS, Chen YS, Zheng H, Krogstad M, Wang SG, Qiu Y, Rodriguez-Rivera JA, Osborn R, Rosenkranz S, Norman MR, Mitchell JF. Intertwined density waves in a metallic nickelate. Nat Commun 2020; 11:6003. [PMID: 33243978 PMCID: PMC7691989 DOI: 10.1038/s41467-020-19836-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 11/03/2020] [Indexed: 11/09/2022] Open
Abstract
Nickelates are a rich class of materials, ranging from insulating magnets to superconductors. But for stoichiometric materials, insulating behavior is the norm, as for most late transition metal oxides. Notable exceptions are the 3D perovskite LaNiO3, an unconventional paramagnetic metal, and the layered Ruddlesden-Popper phases R4Ni3O10, (R = La, Pr, Nd). The latter are particularly intriguing because they exhibit an unusual metal-to-metal transition. Here, we demonstrate that this transition results from an incommensurate density wave with both charge and magnetic character that lies closer in its behavior to the metallic density wave seen in chromium metal than the insulating stripes typically found in single-layer nickelates like La2-xSrxNiO4. We identify these intertwined density waves as being Fermi surface-driven, revealing a novel ordering mechanism in this nickelate that reflects a coupling among charge, spin, and lattice degrees of freedom that differs not only from the single-layer materials, but from the 3D perovskites as well. Layered Ruddlesden-Popper structure nickelates R4Ni3O10 (R = La,Pr) show an unusual metal-to-metal transition, but its origin has remained elusive for more than two decades. Here, the authors show that this transition results from intertwined density waves that arise from a coupling between charge and spin degrees of freedom
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Klein RA, Walsh JPS, Clarke SM, Liu Z, Alp EE, Bi W, Meng Y, Altman AB, Chow P, Xiao Y, Norman MR, Rondinelli JM, Jacobsen SD, Puggioni D, Freedman DE. Pressure-Induced Collapse of Magnetic Order in Jarosite. PHYSICAL REVIEW LETTERS 2020; 125:077202. [PMID: 32857531 DOI: 10.1103/physrevlett.125.077202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
We report a pressure-induced phase transition in the frustrated kagomé material jarosite at ∼45 GPa, which leads to the disappearance of magnetic order. Using a suite of experimental techniques, we characterize the structural, electronic, and magnetic changes in jarosite through this phase transition. Synchrotron powder x-ray diffraction and Fourier transform infrared spectroscopy experiments, analyzed in aggregate with the results from density functional theory calculations, indicate that the material changes from a R3[over ¯]m structure to a structure with a R3[over ¯]c space group. The resulting phase features a rare twisted kagomé lattice in which the integrity of the equilateral Fe^{3+} triangles persists. Based on symmetry arguments we hypothesize that the resulting structural changes alter the magnetic interactions to favor a possible quantum paramagnetic phase at high pressure.
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Broholm C, Cava RJ, Kivelson SA, Nocera DG, Norman MR, Senthil T. Quantum spin liquids. Science 2020; 367:367/6475/eaay0668. [DOI: 10.1126/science.aay0668] [Citation(s) in RCA: 271] [Impact Index Per Article: 67.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Zhang J, Pajerowski DM, Botana AS, Zheng H, Harriger L, Rodriguez-Rivera J, Ruff JPC, Schreiber NJ, Wang B, Chen YS, Chen WC, Norman MR, Rosenkranz S, Mitchell JF, Phelan D. Spin Stripe Order in a Square Planar Trilayer Nickelate. PHYSICAL REVIEW LETTERS 2019; 122:247201. [PMID: 31322403 DOI: 10.1103/physrevlett.122.247201] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/14/2019] [Indexed: 06/10/2023]
Abstract
Trilayer nickelates, which exhibit a high degree of orbital polarization combined with an electron count (d^{8.67}) corresponding to overdoped cuprates, have been identified as a promising candidate platform for achieving high-T_{c} superconductivity. One such material, La_{4}Ni_{3}O_{8}, undergoes a semiconductor-insulator transition at ∼105 K, which was recently shown to arise from the formation of charge stripes. However, an outstanding issue has been the origin of an anomaly in the magnetic susceptibility at the transition and whether it signifies the formation of spin stripes akin to single layer nickelates. Here we report single crystal neutron diffraction measurements (both polarized and unpolarized) that establish that the ground state is indeed magnetic. The ordering is modeled as antiferromagnetic spin stripes that are commensurate with the charge stripes, the magnetic ordering occurring in individual trilayers that are essentially uncorrelated along the crystallographic c axis. A comparison of the charge and spin stripe order parameters reveals that, in contrast to single-layer nickelates such as La_{2-x}Sr_{x}NiO_{4} as well as related quasi-2D oxides including manganites, cobaltates, and cuprates, these orders uniquely appear simultaneously, thus demonstrating a stronger coupling between spin and charge than in these related low-dimensional correlated oxides.
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Micklitz T, Norman MR. Symmetry-Enforced Line Nodes in Unconventional Superconductors. PHYSICAL REVIEW LETTERS 2017; 118:207001. [PMID: 28581811 DOI: 10.1103/physrevlett.118.207001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Indexed: 06/07/2023]
Abstract
We classify line nodes in superconductors with strong spin-orbit interactions and time-reversal symmetry, where the latter may include nonprimitive translations in the magnetic Brillouin zone to account for coexistence with antiferromagnetic order. We find four possible combinations of irreducible representations of the order parameter on high-symmetry planes, two of which allow for line nodes in pseudospin-triplet pairs and two that exclude conventional fully gapped pseudospin-singlet pairs. We show that the former can only be realized in the presence of band-sticking degeneracies, and we verify their topological stability using arguments based on Clifford algebra extensions. Our classification exhausts all possible symmetry protected line nodes in the presence of spin-orbit coupling and a (generalized) time-reversal symmetry. Implications for existing nonsymmorphic and antiferromagnetic superconductors are discussed.
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Zhang J, Chen YS, Phelan D, Zheng H, Norman MR, Mitchell JF. Stacked charge stripes in the quasi-2D trilayer nickelate La4Ni3O8. Proc Natl Acad Sci U S A 2016; 113:8945-50. [PMID: 27462109 PMCID: PMC4987796 DOI: 10.1073/pnas.1606637113] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The quasi-2D nickelate La4Ni3O8 (La-438), consisting of trilayer networks of square planar Ni ions, is a member of the so-called T' family, which is derived from the Ruddlesden-Popper (R-P) parent compound La4Ni3O10-x by removing two oxygen atoms and rearranging the rock salt layers to fluorite-type layers. Although previous studies on polycrystalline samples have identified a 105-K phase transition with a pronounced electronic and magnetic response but weak lattice character, no consensus on the origin of this transition has been reached. Here, we show using synchrotron X-ray diffraction on high-pO2 floating zone-grown single crystals that this transition is associated with a real space ordering of charge into a quasi-2D charge stripe ground state. The charge stripe superlattice propagation vector, q = (2/3, 0, 1), corresponds with that found in the related 1/3-hole doped single-layer R-P nickelate, La5/3Sr1/3NiO4 (LSNO-1/3; Ni(2.33+)), with orientation at 45° to the Ni-O bonds. The charge stripes in La-438 are weakly correlated along c to form a staggered ABAB stacking that reduces the Coulomb repulsion among the stripes. Surprisingly, however, we find that the charge stripes within each trilayer of La-438 are stacked in phase from one layer to the next, at odds with any simple Coulomb repulsion argument.
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Norman MR. Materials design for new superconductors. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:074502. [PMID: 27214291 DOI: 10.1088/0034-4885/79/7/074502] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Since the announcement in 2011 of the Materials Genome Initiative by the Obama administration, much attention has been given to the subject of materials design to accelerate the discovery of new materials that could have technological implications. Although having its biggest impact for more applied materials like batteries, there is increasing interest in applying these ideas to predict new superconductors. This is obviously a challenge, given that superconductivity is a many body phenomenon, with whole classes of known superconductors lacking a quantitative theory. Given this caveat, various efforts to formulate materials design principles for superconductors are reviewed here, with a focus on surveying the periodic table in an attempt to identify cuprate analogues.
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Chatterjee U, Zhao J, Iavarone M, Di Capua R, Castellan JP, Karapetrov G, Malliakas CD, Kanatzidis MG, Claus H, Ruff JPC, Weber F, van Wezel J, Campuzano JC, Osborn R, Randeria M, Trivedi N, Norman MR, Rosenkranz S. Emergence of coherence in the charge-density wave state of 2H-NbSe2. Nat Commun 2015; 6:6313. [PMID: 25687135 PMCID: PMC4339883 DOI: 10.1038/ncomms7313] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 01/19/2015] [Indexed: 12/02/2022] Open
Abstract
A charge-density wave (CDW) state has a broken symmetry described by a complex order parameter with an amplitude and a phase. The conventional view, based on clean, weak-coupling systems, is that a finite amplitude and long-range phase coherence set in simultaneously at the CDW transition temperature Tcdw. Here we investigate, using photoemission, X-ray scattering and scanning tunnelling microscopy, the canonical CDW compound 2H-NbSe2 intercalated with Mn and Co, and show that the conventional view is untenable. We find that, either at high temperature or at large intercalation, CDW order becomes short-ranged with a well-defined amplitude, which has impacts on the electronic dispersion, giving rise to an energy gap. The phase transition at Tcdw marks the onset of long-range order with global phase coherence, leading to sharp electronic excitations. Our observations emphasize the importance of phase fluctuations in strongly coupled CDW systems and provide insights into the significance of phase incoherence in ‘pseudogap’ states. Charge density waves are described by a complex order parameter whose amplitude is expected to vanish at the transition temperature. This study shows that the transition in 2H-NbSe2 is driven by fluctuations of the phase of the order parameter, with a finite amplitude surviving in the disordered state.
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Paul I, Pépin C, Norman MR. Equivalence of single-particle and transport lifetimes from hybridization fluctuations. PHYSICAL REVIEW LETTERS 2013; 110:066402. [PMID: 23432282 DOI: 10.1103/physrevlett.110.066402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Indexed: 06/01/2023]
Abstract
Single band theories of quantum criticality successfully describe a single-particle lifetime with non-Fermi liquid temperature dependence, but they fail to obtain a charge transport rate with the same dependence unless the interaction is assumed to be momentum independent. Here we demonstrate that a quantum critical material, with a long-range mode that transmutes electrons between light and heavy bands, exhibits a quasilinear temperature dependence for both the single-particle and the charge transport lifetimes, despite the strong momentum dependence of the interaction.
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Castellan JP, Rosenkranz S, Goremychkin EA, Chung DY, Todorov IS, Kanatzidis MG, Eremin I, Knolle J, Chubukov AV, Maiti S, Norman MR, Weber F, Claus H, Guidi T, Bewley RI, Osborn R. Effect of Fermi surface nesting on resonant spin excitations in Ba(1-x)K(x)Fe2As2. PHYSICAL REVIEW LETTERS 2011; 107:177003. [PMID: 22107566 DOI: 10.1103/physrevlett.107.177003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Indexed: 05/31/2023]
Abstract
We report inelastic neutron scattering measurements of the resonant spin excitations in Ba(1-x)K(x)Fe(2)As(2) over a broad range of electron band filling. The fall in the superconducting transition temperature with hole doping coincides with the magnetic excitations splitting into two incommensurate peaks because of the growing mismatch in the hole and electron Fermi surface volumes, as confirmed by a tight-binding model with s(±)-symmetry pairing. The reduction in Fermi surface nesting is accompanied by a collapse of the resonance binding energy and its spectral weight, caused by the weakening of electron-electron correlations.
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Pépin C, Norman MR, Burdin S, Ferraz A. Modulated spin liquid: a new paradigm for URu2Si2. PHYSICAL REVIEW LETTERS 2011; 106:106601. [PMID: 21469819 DOI: 10.1103/physrevlett.106.106601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Indexed: 05/30/2023]
Abstract
We argue that near a Kondo breakdown critical point, a spin liquid with spatial modulations can form. Unlike its uniform counterpart, we find that this occurs via a second order phase transition. The amount of entropy quenched when ordering is of the same magnitude as for an antiferromagnet. Moreover, the two states are competitive, and at low temperatures are separated by a first order phase transition. The modulated spin liquid we find breaks Z4 symmetry, as recently seen in the hidden order phase of URu2Si2. Based on this, we suggest that the modulated spin liquid is a viable candidate for this unique phase of matter.
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Norman MR, Kaminski A, Rosenkranz S, Campuzano JC. Comment on "Circular dichroism in the angle-resolved photoemission spectrum of the high-temperature Bi2Sr2CaCu2O8+δ superconductor: can these measurements be interpreted as evidence for time-reversal symmetry breaking?". PHYSICAL REVIEW LETTERS 2010; 105:189701-189702. [PMID: 21231148 DOI: 10.1103/physrevlett.105.189701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Indexed: 05/30/2023]
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Norman MR, Micklitz T. How to measure a spinon fermi surface. PHYSICAL REVIEW LETTERS 2009; 102:067204. [PMID: 19257629 DOI: 10.1103/physrevlett.102.067204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 10/30/2008] [Indexed: 05/27/2023]
Abstract
We propose an experiment to identify the potential existence of a spinon Fermi surface by looking for oscillatory coupling between two ferromagnets via a spin liquid spacer. Three candidate spin liquids are investigated, and it is found out that in all cases long period oscillations should be present, the period of which would identify the Fermi wave vector of the spinon surface.
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Saniz R, Norman MR, Freeman AJ. Orbital mixing and nesting in the bilayer manganites La2-2xSr1+2xMn2O7. PHYSICAL REVIEW LETTERS 2008; 101:236402. [PMID: 19113571 DOI: 10.1103/physrevlett.101.236402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Indexed: 05/27/2023]
Abstract
A first principles study of La2-2xSr1+2xMn2O7 compounds for doping levels 0.3 < or = x < or = 0.5 shows that the low energy electronic structure of the majority spin carriers is determined by strong momentum-dependent interactions between the Mn eg dx2-y2 and d3z2-r2 orbitals, which, in addition to an x-dependent Jahn-Teller distortion, differ in the ferromagnetic and antiferromagnetic phases. The Fermi surface exhibits nesting behavior that is reflected by peaks in the static susceptibility, whose positions as a function of momentum have a nontrivial dependence on x.
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Kanigel A, Chatterjee U, Randeria M, Norman MR, Koren G, Kadowaki K, Campuzano JC. Evidence for pairing above the transition temperature of cuprate superconductors from the electronic dispersion in the pseudogap phase. PHYSICAL REVIEW LETTERS 2008; 101:137002. [PMID: 18851483 DOI: 10.1103/physrevlett.101.137002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Indexed: 05/26/2023]
Abstract
In the underdoped high temperature superconductors, instead of a complete Fermi surface above Tc, only disconnected Fermi arcs appear, separated by regions that still exhibit an energy gap. We show that in this pseudogap phase, the energy-momentum relation of electronic excitations near EF behaves like the dispersion of a normal metal on the Fermi arcs, but like that of a superconductor in the gapped regions. We argue that this dichotomy in the dispersion is difficult to reconcile with a competing order parameter, but is consistent with pairing without condensation.
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Shi M, Chang J, Pailhés S, Norman MR, Campuzano JC, Månsson M, Claesson T, Tjernberg O, Bendounan A, Patthey L, Momono N, Oda M, Ido M, Mudry C, Mesot J. Coherent d-wave superconducting gap in underdoped La2-xSrxCuO4 by angle-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2008; 101:047002. [PMID: 18764357 DOI: 10.1103/physrevlett.101.047002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Indexed: 05/26/2023]
Abstract
We present angle-resolved photoemission spectroscopy data on moderately underdoped La1.855Sr0.145CuO4 at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple d-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La1.895Sr0.105CuO4 also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV.
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Kanigel A, Chatterjee U, Randeria M, Norman MR, Souma S, Shi M, Li ZZ, Raffy H, Campuzano JC. Protected nodes and the collapse of Fermi arcs in high-T{c} cuprate superconductors. PHYSICAL REVIEW LETTERS 2007; 99:157001. [PMID: 17995204 DOI: 10.1103/physrevlett.99.157001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Indexed: 05/25/2023]
Abstract
Angle resolved photoemission on underdoped Bi2Sr2CaCu2O8 reveals that the magnitude and d-wave anisotropy of the superconducting state energy gap are independent of temperature all the way up to T{c}. This lack of T variation of the entire k-dependent gap is in marked contrast to mean field theory. At T{c} the point nodes of the d-wave gap abruptly expand into finite length "Fermi arcs." This change occurs within the width of the resistive transition, and thus the Fermi arcs are not simply thermally broadened nodes but rather a unique signature of the pseudogap phase.
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Paul I, Pépin C, Norman MR. Kondo breakdown and hybridization fluctuations in the kondo-heisenberg lattice. PHYSICAL REVIEW LETTERS 2007; 98:026402. [PMID: 17358626 DOI: 10.1103/physrevlett.98.026402] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Indexed: 05/14/2023]
Abstract
We study the deconfined quantum critical point of the Kondo-Heisenberg lattice in three dimensions using a fermionic representation for the localized spins. The mean-field phase diagram exhibits a zero temperature quantum critical point separating a spin liquid phase where the hybridization vanishes and a Kondo phase where it does not. Two solutions can be stabilized in the Kondo phase: namely, a uniform hybridization when the band masses of the conduction electrons and the spinons have the same sign, and a modulated one when they have opposite sign. For the uniform case, we show that above a very small temperature scale, the critical fluctuations associated with the vanishing hybridization have dynamical exponent z=3, giving rise to a resistivity that has a TlogT behavior. We also find that the specific heat coefficient diverges logarithmically in temperature, as observed in a number of heavy fermion metals.
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Dzero M, Norman MR, Paul I, Pépin C, Schmalian J. Quantum critical end point for the Kondo volume collapse model. PHYSICAL REVIEW LETTERS 2006; 97:185701. [PMID: 17155553 DOI: 10.1103/physrevlett.97.185701] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Indexed: 05/12/2023]
Abstract
The Kondo volume collapse describes valence transitions in f-electron metals and is characterized by a line of first order transitions in the pressure-temperature phase plane terminated at critical end points. We analyze the quantum critical end point, when the lower end point is tuned to T=0, and determine the specific heat, thermal expansion, and compressibility. We find that the inclusion of quantum critical fluctuations leads to a novel bifurcation of the first order phase line. Finally, we show that critical strain fluctuations can cause both, superconductivity and non-Fermi liquid behavior near the critical point.
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Chatterjee U, Shi M, Kaminski A, Kanigel A, Fretwell HM, Terashima K, Takahashi T, Rosenkranz S, Li ZZ, Raffy H, Santander-Syro A, Kadowaki K, Norman MR, Randeria M, Campuzano JC. Nondispersive fermi arcs and the absence of charge ordering in the pseudogap phase of Bi2Sr2CaCu2O8+delta. PHYSICAL REVIEW LETTERS 2006; 96:107006. [PMID: 16605781 DOI: 10.1103/physrevlett.96.107006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Indexed: 05/08/2023]
Abstract
The autocorrelation of angle resolved photoemission data from the high temperature superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) shows distinct peaks in momentum space which disperse with binding energy in the superconducting state, but not in the pseudogap phase. Although it is tempting to attribute a nondispersive behavior in momentum space to charge ordering, a deconstruction of the autocorrelation reveals that the nondispersive peaks arise from the tips of the Fermi arcs, which themselves do not change with binding energy.
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Eremin I, Morr DK, Chubukov AV, Bennemann KH, Norman MR. Novel neutron resonance mode in dx2-y2-wave superconductors. PHYSICAL REVIEW LETTERS 2005; 94:147001. [PMID: 15904094 DOI: 10.1103/physrevlett.94.147001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Indexed: 05/02/2023]
Abstract
We show that a new resonant magnetic excitation at incommensurate momenta, observed recently by inelastic neutron scattering experiments on YBa2Cu3O6.85 and YBa2Cu3O6.6, is a spin exciton. Its location in the Brillouin zone and its frequency are determined by the momentum dependence of the particle-hole continuum. We identify several features that distinguish this novel mode from the previous resonance mode observed near Q=(pi,pi).
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Creed TJ, Norman MR, Probert CSJ, Harvey RF, Shaw IS, Smithson J, Anderson J, Moorghen M, Gupta J, Shepherd NA, Dayan CM, Hearing SD. Basiliximab (anti-CD25) in combination with steroids may be an effective new treatment for steroid-resistant ulcerative colitis. Aliment Pharmacol Ther 2003; 18:65-75. [PMID: 12848627 DOI: 10.1046/j.1365-2036.2003.01639.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Steroid resistance represents a major clinical problem in the treatment of ulcerative colitis. In vitro, interleukin-2 renders lymphocytes steroid resistant. AIM To explore the therapeutic potential of interleukin-2 receptor blockade in steroid-resistant ulcerative colitis with both in vitro measures and a pilot in vivo study. METHODS Ten patients with steroid-resistant ulcerative colitis received a single bolus of 40 mg of intravenous basiliximab plus steroid treatment in an open-label, uncontrolled, 24-week study. The outcome was assessed using the Ulcerative Colitis Symptom Score, rectal biopsy and Inflammatory Bowel Disease Questionnaire. Lymphocyte steroid sensitivity was measured in vitro in 39 subjects in the presence or absence of basiliximab. RESULTS Nine of the 10 patients achieved clinical remission within 8 weeks. At 24 weeks, seven patients were in clinical remission. Marked improvement in the Ulcerative Colitis Symptom Score was seen by 1 week (P = 0.004) and on rectal biopsy and Inflammatory Bowel Disease Questionnaire by 2 weeks (both P < 0.05). Improvements persisted to 24 weeks (Ulcerative Colitis Symptom Score, Inflammatory Bowel Disease Questionnaire, both P < 0.005). Eight of the nine responders relapsed (median, 9 weeks), but remission was re-achieved with further corticosteroids and the addition of azathioprine. At 24 weeks, seven patients were in full clinical remission, five off all steroid therapy. In vitro measurement of lymphocyte steroid sensitivity demonstrated steroid resistance in 22% of subjects. All were rendered steroid sensitive in the presence of basiliximab. CONCLUSIONS Basiliximab appears to be effective at inducing remission in steroid-resistant ulcerative colitis. In vitro, basiliximab also produced a dramatic increase in lymphocyte steroid sensitivity in healthy subjects. Confirmation in randomized controlled studies is required.
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