Unified picture of N el order destruction, d-wave superconductivity and the pseudogap phase for high<i>T</i><sub>c</sub>cuprates

Morinari, Takao

doi:10.1088/0953-2048/16/5/314

Cited by 4 publications

(4 citation statements)

References 92 publications

(100 reference statements)

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“…The superconductivity observed in the LaAg 1 –x Mn x alloys with x ≥ 0.05 has many striking features that do not fit into 40 the standard BCS framework of conventional phonon‐mediated superconductivity. On the other hand, with the AFM critical phase boundary ( y 0 = 0) identified as $x_{{\rm c}} \cong 0.05$ , the specific heat and resistivity data 40 exactly reproduce the predictions, based on the self‐consistently renormalized spin fluctuation theories 30–38, that (a) at the AFM critical phase boundary, the electronic part of specific heat $C_{{\rm SF}} /T{\propto} {-} T^{1/2} $ at low temperatures, and varies as −log T at higher temperatures (Fig. 5) while concomitantly, the resistivity varies with temperature as $\rho (T,\,H = 0){\propto} {-} T^{3/2} $ at low temperatures (Fig.…”

Section: Unconventional Superconductivitysupporting

confidence: 55%

“…This unconventional form of superconductivity is thought to arise from the d ‐wave spin‐singlet ( p ‐wave spin‐triplet) pairing of electrons caused by interactions mediated by AFM (FM) spin fluctuations. The spin fluctuation mechanism has the ability to explain 30–38, on the same physical footing, very low superconducting transition temperatures $T_{{\rm c}} \approx 1\,{\rm K}$ or lower in some of the above‐mentioned 3D superconductors as against strongly enhanced AFM susceptibilities and high T c s ≈ 100 K in the quasi‐two‐dimensional (2D) perovskite oxides.…”

Section: Unconventional Superconductivitymentioning

confidence: 99%

“…The spin fluctuation models make specific predictions 30–38 concerning the criteria for observing magnetically mediated superconductivity at elevated temperatures. These predictions are: (i) irrespective of the spatial dimensionality of the system, AFM spin fluctuations rather than their FM counterpart lead to an enhanced pairing energy and hence result in higher T c and greater robustness against impurities, (ii) T c can be as large in 3D systems as in 2D ones provided the normalized bandwidths and the AFM spin fluctuation parameters take on similar values in the two cases, and (iii) in both the spatial dimensions, T c is extremely sensitive to the frequency spread of the AFM spin fluctuations; the larger the frequency spread, the higher the T c .…”

Section: Unconventional Superconductivitymentioning

confidence: 99%

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Novel physical phenomena in proximity to quantum critical point

Kaul¹

2011

Physica Status Solidi (b)

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The weakly interacting quasiparticle picture of a Fermi liquid proposed by Landau (the phonon-mediated electron-pairing theory of Bardeen-Cooper-Schrieffer) provided a coherent theoretical basis for understanding how the interactions between electrons affect the low-temperature properties of metals (metallic superconductors) for the past five decades. However, in recent years, strong departures from the predictions of these theories have been observed in an increasingly large number of systems, particularly in the vicinity of a quantum phase transition (QPT). This paper briefly reviews the current state of research in the areas of the non-Fermi liquid (NFL) state, spin-fluctuation-mediated anisotropic superconductivity, and Bose-Einstein condensation (BEC) of magnons (bosonic quasiparticle excitations) near a quantum critical point (QCP), which is induced by external pressure or doping or nanocrystallite size or magnetic fields. 1 Preamble Early theoretical proposition [1] that the ground state of a quantum system at T ¼ 0 changes from ordered to disordered when some control parameter (e.g., a coupling constant) in the Hamiltonian attains a critical value [the quantum critical point (QCP)], shifted the scientific focus away from the classical phase transitions, which occur at finite temperatures and are driven by thermal fluctuations of the order parameter with temperature as a control parameter. T ¼ 0 or T 6 ¼ 0 is not the only distinguishing feature between quantum and classical phase transitions. Unlike in classical phase transitions, the statics and dynamics in quantum systems at T ¼ 0 are inextricably linked with the result that a d-dimensional quantum system at T ¼ 0 can be considered [1, 2] as a (d þ z)-dimensional classical system, where z is the critical exponent that characterizes the dynamics in the vicinity of a quantum phase transition (QPT). Although a QPT occurs at zero temperature, the behavior of the system at temperatures sufficiently close to the QCP is still governed by quantum critical effects [1,2]. The underlying QCP effects can thus be studied experimentally at finite but low temperatures even though the QCP at T ¼ 0 is inaccessible to experiments. In practice, external pressure ( p) or doping (x, chemical pressure) or an external magnetic field (H) is used as a control parameter to tune the spin system to the QCP by bringing down the magnetic order-disorder transition temperature (i.e., Curie temperature, T C , for a ferromagnet or Néel temperature, T N , for an antiferromagnet) to almost zero when the control parameter approaches a threshold p c or x c or H c .In recent years, discovery of new physical phenomena near the QCP such as the non-Fermi liquid (NFL) state, unconventional superconductivity and Bose-Einstein condensation (BEC) of quasiparticle excitations necessitated a constant revision in our understanding of how interactions between electrons influence the low-temperature properties of metals, in particular and spin systems, in general. In the following sections, these phenome...

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Section: Unconventional Superconductivitysupporting

confidence: 55%

Section: Unconventional Superconductivitymentioning

confidence: 99%

Section: Unconventional Superconductivitymentioning

confidence: 99%

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Novel physical phenomena in proximity to quantum critical point

Kaul¹

2011

Physica Status Solidi (b)

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“…111,112 If there were something topological at work in individual cuprate copper oxide layers, for instance a Chern-Simons term or some kind of vortices, then possibly when the layers are stacked they could produce a Weyl phase and Fermi arcs. [113][114][115] • Electron/hole loops. As briefly outlined earlier in this text, weak (anti)localization is caused by Cooperons tracing loops.…”

Section: Postscript: How To Do Topology In a Strongly Interacting Mat...mentioning

confidence: 99%

Indications for Topological Physics in High-$T_c$ Materials

Sacksteder

2020

Preprint

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Research on high-Tc superconductors has generally not focused on analysis of the topological structure of electronic bands in these materials. In this article we collate and discuss several wellknown experimental observables that signal that certain signatures of topology may be present. The topological signatures suggested by experiment include dimensional reduction, electronic transport determined by loop statistics, a winding number, Weyl fermions, and others. We suggest that topology, in a wider sense than band topology, may be key to the mechanism of high-Tc superconductivity.

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Antiferromagnetic-spin-fluctuation-mediated pairing as a likely mechanism for unconventional superconductivity in LaAg1−cMnc alloys

Kumar

Kaul

Fernández

et al. 2009

Journal of Applied Physics

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Electrical resistivity, ac magnetic susceptibility, specific heat, dc magnetization, and dc magnetic susceptibility of superconducting LaAg1−cMnc alloys with c=0.0, 0.025, 0.05. 0.1, 0.2, and 0.3 have been measured in the temperature range of 0.35 K≤T≤300 K at external magnetic fields ranging from 0 to 90 kOe with a view to unravel the exact nature of the superconducting ground state. In these alloys, each Mn atom carries a magnetic moment of ≅4μB. A comparison of the results of these investigations with the predictions of the existing theoretical models permits us to make a number of interesting observations that include the following. The intermetallic compound LaAg is an archetypal Bardeen–Cooper–Schrieffer (BCS) spin-singlet isotropic even-parity s-wave superconductor with a superconducting transition temperature of Tc=0.97 K. At low solute concentrations of c≈0.03, Mn substitutes for La at the La sublattice sites in the LaAg parent compound and Tc suddenly drop from 0.97 to temperatures below 0.35 K, reflecting thereby the destruction of conventional phonon-mediated s-wave superconductivity of the LaAg host by pair-breaking magnetic (Mn) impurities. At a threshold concentration of Mn, c≅0.05 (which corresponds to the antiferromagnetic instability/critical phase boundary in the magnetic phase diagram), superconducting gap opens up, Tc abruptly shoots up to 5 K, and unconventional superconductivity sets in at ambient pressure for T≤Tc. Beyond this threshold concentration, Mn has exclusive site preference for Ag at the Ag sublattice sites in LaAg and Tc increases from 5 to 6 K. The unconventional nature of superconductivity at these solute concentrations is signaled by strong departures from the BCS predictions. We present ample experimental evidence that favors antiferromagnetic-spin-fluctuation-mediated pairing as the most likely mechanism for the unconventional (d-wave) superconductivity observed in LaAg1−cMnc alloys with c≥0.05.

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Unified picture of N el order destruction, d-wave superconductivity and the pseudogap phase for highT_ccuprates

Cited by 4 publications

References 92 publications

Novel physical phenomena in proximity to quantum critical point

Novel physical phenomena in proximity to quantum critical point

Indications for Topological Physics in High-$T_c$ Materials

Antiferromagnetic-spin-fluctuation-mediated pairing as a likely mechanism for unconventional superconductivity in LaAg1−cMnc alloys

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Unified picture of N el order destruction, d-wave superconductivity and the pseudogap phase for highTccuprates

Cited by 4 publications

References 92 publications

Novel physical phenomena in proximity to quantum critical point

Novel physical phenomena in proximity to quantum critical point

Indications for Topological Physics in High-$T_c$ Materials

Antiferromagnetic-spin-fluctuation-mediated pairing as a likely mechanism for unconventional superconductivity in LaAg1−cMnc alloys

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Unified picture of N el order destruction, d-wave superconductivity and the pseudogap phase for highT_ccuprates