Intra-unit-cell nematic charge order in the titanium-oxypnictide family of superconductors

Frandsen, Benjamin A.; Božin, Emil S.; Hu, Hefei; Zhu, Yimei; Nozaki, Y.; Kageyama, Hiroshi; Uemura, Y. J.; Yin, Wei‐Guo; Billinge, Simon J. L.

doi:10.1038/ncomms6761

Cited by 27 publications

(68 citation statements)

References 49 publications

(92 reference statements)

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“…There are three possible sources for considerable V : (i) Strongly correlated metals are generally bad metals with large resistivity of the order of mΩ·cm and small optical Drude peak. Therefore, the electrostatic screening does not work well in those systems [14,[75][76][77][78]. (ii) In mean-field theory, the local constraint of no-double occupancy at each site is reinforced only globally.…”

Section: Discussionmentioning

confidence: 99%

“…This generally yields a dome structure of the SC critical temperature T c as a function of the doping level x. The parent competing order (CO) ranges from the antiferormagnetic spin order in cuprates [4][5][6][7][8] and heavy-fermion rare-earth compounds [9], to the ferro-orbital and antiferormagnetic spin dipolar/quadruplar orders in iron pnictides/chalcogenides [10][11][12][13], and to the charge order in titanium oxypnictides [14] and transition-metal dichalcogendies [15]. A particularly interesting case is the cuprate high-temperature superconductors, where the parent and SC phases do not appear to coexist but the phase competition is actually intensified by the emerging of a "strange metal" normal state with pseudogap opening at a temperature T * well above T c in the underdoped regime [5].…”

Section: Introductionmentioning

confidence: 99%

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Phase competition and anomalous thermal evolution in high-temperature superconductors

Zhou

Yin

et al. 2017

Phys. Rev. B

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The interplay of competing orders is relevant to high-temperature superconductivity known to emerge upon suppression of a parent antiferromagnetic order typically via charge doping. How such interplay evolves at low temperature-in particular at what doping level the zero-temperature quantum critical point (QCP) is located-is still elusive because it is masked by the superconducting state. The QCP had long been believed to follow a smooth extrapolation of the characteristic temperature T * for the strange normal state well above the superconducting transition temperature. However, recently the T * within the superconducting dome was reported to unexpectedly exhibit back-bending likely in the cuprate Bi2Sr2CaCu2O 8+δ . Here we show that the original and revised phase diagrams can be understood in terms of weak and moderate competitions, respectively, between superconductivity and a pseudogap state such as d-density-wave or spin-density-wave, based on both Ginzburg-Landau theory and the realistic t-t ′ -t ′′ -J-V model for the cuprates. We further found that the calculated temperature and doping-level dependence of the quasiparticle spectral gap and Raman response qualitatively agrees with the experiments. In particular, the T * back-bending can provide a simple explanation of the observed anomalous two-step thermal evolution dominated by the superconducting gap and the pseudogap, respectively. Our results imply that the revised phase diagram is likely to take place in high-temperature superconductors.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Phase competition and anomalous thermal evolution in high-temperature superconductors

Zhou

Yin

et al. 2017

Phys. Rev. B

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“…The increased relaxation of the polarization could not be found below TDW, indicating the absence of magnetic order. Frandsen et al performed low-temperature neutron diffraction measurements and found tiny lattice distortions from tetragonal to orthorhombic where the orthorhombicity parameter η = 2 × (a − b)/(a + b) reaches only 0.22% and 0.05% at 20 K for BaTi2As2O and BaTi2Sb2O, respectively [19]. The lattice distortion is much smaller than that observed in Jahn-Teller compounds and iron pnictides.…”

Section: The Dw Instability In Bati 2 Pn 2 Omentioning

confidence: 99%

“…At present, eight titanium pnictide oxides Na 2 Ti 2 Pn 2 O (Pn = As, Sb), (SrF) 2 Ti 2 Pn 2 O (Pn = As, Sb, Bi), and BaTi 2 Pn 2 O (Pn = As, Sb, Bi) have been synthesized, but only BaTi 2 Pn 2 O (Pn = Sb, Bi) shows superconductivity [11,[14][15][16][17]. Though BaTi 2 Pn 2 O is not high-T c superconductor, several unique and attracting physical properties have been found: two superconducting domes in the phase diagram of isovalent solid solutions of BaTi 2 (Sb 1-x Bi x ) 2 O and unconventional DW instability [18,19]. In this short review, the superconductivity and DW instability in the titanium pnictide oxides will be discussed from discovery to recent progress.…”

Section: Introductionmentioning

confidence: 99%

Titanium Pnictide Oxide Superconductors

Yajima

2017

Condensed Matter

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Abstract:In 2012, a novel superconductor BaTi 2 Sb 2 O was found in the layered titanium pnictide oxides ATi 2 Pn 2 O. A related superconductor BaTi 2 Bi 2 O was subsequently discovered in 2013. The structure of these materials consists of alternate stacking of superconducting Ti 2 Pn 2 O layers and Ba blocking layers, which is somewhat similar to high-T c cuprates since the Ti 2 Pn 2 O layer contains an anti-CuO 2 -type Ti 2 O square lattice. In addition to the structural similarity to the well-known high-T c superconductors, BaTi 2 Pn 2 O shows unique physical properties: two superconducting domes appear in the electronic phase diagram for solid solutions of BaTi 2 (Sb 1-x Bi x ) 2 O and a unique density-wave instability which coexists with superconductivity. In this short review, the early studies of titanium pnictide oxides, the discovery of novel superconductors BaTi 2 Pn 2 O, and recent progress are summarized.

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“…The double stripe (DS) magnetic ground state has been proposed in BaTi 2 Sb 2 O [20][21][22][23] and found in the 11 system Fe 1+y Se x Te 1−x [24,25], which exhibits magnetic order with the commensurate ordering vector Q = (π/2,π/2) [26][27][28]. DS order can be understood as the Néel ordering of a four-spin plaquette with three up and one down spins, which results in double-width ferromagnetic (FM) stripes along one diagonal direction and double-width antiferromagnetic(AFM) stripes along the other, see Fig.…”

Section: Introductionmentioning

confidence: 99%

Emergent Ising degrees of freedom above a double-stripe magnetic ground state

Zhang

Flint

2017

Phys. Rev. B

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Double-stripe magnetism [ Q = ( π / 2 , π / 2 ) ] has been proposed as the magnetic ground state for both the iron-telluride and BaTi 2 Sb 2 O families of superconductors. Double-stripe order is captured within a J 1 − J 2 − J 3 Heisenberg model in the regime J 3 ≫ J 2 ≫ J 1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector ( π , π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one. Double-stripe magnetism [Q = (π/2,π/2)] has been proposed as the magnetic ground state for both the iron-telluride and BaTi 2 Sb 2 O families of superconductors. Double-stripe order is captured within a J 1 -J 2 -J 3 Heisenberg model in the regime J 3 J 2 J 1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π,π). Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one. Disciplines Condensed Matter Physics

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Intra-unit-cell nematic charge order in the titanium-oxypnictide family of superconductors

Cited by 27 publications

References 49 publications

Phase competition and anomalous thermal evolution in high-temperature superconductors

Phase competition and anomalous thermal evolution in high-temperature superconductors

Titanium Pnictide Oxide Superconductors

Emergent Ising degrees of freedom above a double-stripe magnetic ground state

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