Spin-Ordering Quantum Transitions of Superconductors in a Magnetic Field

Demler, Eugene; Sachdev, Subir; Zhang, Ying

doi:10.1103/physrevlett.87.067202

Cited by 272 publications

(455 citation statements)

References 18 publications

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“…While the underlying continuum approximations may be called into question at high fields, such a model [23] gives quantitative results in good agreement with our T=0 data, as shown in fig. 3b.…”

supporting

confidence: 85%

“…Our data suggest that the antiferromagnetic regions are much greater than this (ζ>400Å) and extend well beyond the vortex cores into the superconducting areas. Alternatively there could be interactions between the vortices that lead to coherent long range antiferromagnetic order without the magnetism spreading beyond the cores; but then the corresponding Néel temperature would be a strong function of the 4 intervortex spacing, controlled by H, whereas our onset temperature is approximately fieldindependent.More recent computations motivated by our experiments have relaxed SO(5) symmetry to allow co-existence of superconductivity and magnetism with the antiferromagnetic correlations extending beyond the vortex core into the bulk of the crystal [22,23]. While the underlying continuum approximations may be called into question at high fields, such a model [23] gives quantitative results in good agreement with our T=0 data, as shown in fig.…”

supporting

confidence: 81%

“…(b) shows the field-induced signal as a function of field at T=2K (magenta circles). The solid line is a fit to the data of the expression, M 2 (H/H c2 )ln(H c2 /H) deduced by Demler et al [23], with fitted parameter M 2 =0.12µ B 2 /Cu 2+ .…”

Section: Captionmentioning

confidence: 97%

“…Calculations based on this hypothesis predict antiferromagnetic vortices in a magnetic field and have had some success in modeling the data [20][21][22][23]. The original work was performed assuming that the symmetry is exact [20].…”

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confidence: 99%

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Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor

Lake

Rønnow

Christensen

et al. 2002

Nature

540

508

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One view of the cuprate high-transition temperature (high-T c ) superconductors is that they are conventional superconductors where the pairing occurs between weakly interacting quasiparticles, which stand in one-to-one correspondence with the electrons in ordinary metals -although the theory has to be pushed to its limit [1]. An alternative view is that the electrons organize into collective textures (e.g. charge and spin stripes) which cannot be mapped onto the electrons in ordinary metals. The phase diagram, a complex function of various parameters (temperature, doping and magnetic field), should then be approached using quantum field theories of objects such as textures and strings, rather than point-like electrons [2,3,4,5,6]. In an external magnetic field, magnetic flux penetrates type-II superconductors via vortices, each carrying one flux quantum [7]. The vortices form lattices of resistive material embedded in the non-resistive superconductor and can reveal the nature of the ground state -e.g. a conventional metal or an ordered, striped phase -which would have appeared had superconductivity not intervened. Knowledge of this ground state clearly provides the most appropriate starting point for a pairing theory. Here we report that for one high-T c superconductor, the applied field which imposes the vortex lattice, also induces antiferromagnetic order. Ordinary quasiparticle pictures cannot account for the nearly fieldindependent antiferromagnetic transition temperature revealed by our measurements.La 2-x Sr x CuO 4 , is the simplest high-T c superconductor. The undoped compound is an insulating antiferromagnet, where the spin moments on adjacent Cu 2+ ions are antiparallel [8]. Introduction of charge carriers via Sr doping reduces the ordered moment until it vanishes at x<0.13. In addition, for x>0.05 the commensurate antiferromagnetism is replaced by incommensurate order [2,3,9,10], where the repeat distance for the pattern of ordered moments is substantially larger than the spacing between neighbouring copper ions. La 2-x Sr x CuO 4 becomes a 2 superconductor for Sr dopings of 0.06

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supporting

confidence: 85%

supporting

confidence: 81%

Section: Captionmentioning

confidence: 97%

mentioning

confidence: 99%

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Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor

Lake

Rønnow

Christensen

et al. 2002

Nature

540

508

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“…An apparently very natural approach to the problem was developed by Demler et al [18], who constructed a Ginzburg-Landau (GL) theory for competing SDW and SC order in a magnetic field. This phenomenology describes correctly the reduction of condensation energy in the vortex phase of the pure superconductor, and leads to a phase diagram qualitatively consistent with experiments [1].…”

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confidence: 99%

d-Wave superconductivity as a catalyst for antiferromagnetism in underdoped cuprates

et al. 2010

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Abstract. In underdoped high-T c cuprates, d-wave superconductivity competes with antiferromagnetism. It has generally been accepted that suppressing superconductivity leads to the nucleation of spin-density wave (SDW) order with wavevector near (π, π). We show theoretically, for a d-wave superconductor in an applied magnetic field including disorder and electronic correlations, that the creation of SDW order is in fact not simply due to suppression of superconductivity, but rather due to a correlation-induced splitting of an electronic bound state arising from the sign change of the order parameter along quasiparticle trajectories. The induced SDW order is therefore a direct consequence of the d-wave symmetry. The formation of anti-phase domain walls proves to be crucial for explaining the heretofore puzzling temperature dependence of the induced magnetism as measured by neutron diffraction.A superconductor is characterized by a Bardeen-Cooper-Schrieffer (BCS) order parameter k (R), where R is the center-of-mass coordinate of a Cooper pair of electrons with momenta (k, −k). The bulk ground state of such a system is homogeneous, but a spatial perturbation that breaks pairs, e.g. a magnetic impurity, may cause the suppression of k (R) locally. What is revealed when superconductivity is suppressed is the electronic phase in the absence of k , a normal Fermi liquid. Thus the low-energy excitations near magnetic impurities and in the vortex 4 Author to whom any correspondence should be addressed. [9,10] detected magnetic ordering as a wedge-shaped extension of the 'spin glass' phase into the SC dome of the temperature versus doping phase diagram ( figure 1(a)). Lake et al [2] reported that an incommensurate magnetic order similar to the field-induced state was also observed in zero field. Although it also vanished at T c , the ordered magnetic moment in zero field had a T dependence, which was qualitatively different from the field-induced signal. The zero-field signal was attributed to disorder, but the relation between impurities and magnetic ordering remained unclear. Because strong magnetic fluctuations with similar wavevectors are reported at low but nonzero energies in inelastic neutron scattering experiments on these materials, e.g. on optimally doped LSCO samples exhibiting no spin-glass phase in zero field, it is frequently argued that impurities or vortices simply 'freeze' this fluctuating order [11].Describing such a phenomenon theoretically at the microscopic level is difficult due to the inhomogeneity of the interacting system, but it is important if one wishes to explore situations with strong disorder, where the correlations may no longer reflect the intrinsic spin dynamics of the pure system. Such an approach was proposed in a model calculation for an inhomogeneous d-wave superconductor with Hubbard-type correlations treated in the mean field [12]. In this model, a single impurity creates, at sufficiently large Hubbard interaction U and impurity potential strength V imp , a droplet of staggered magn...

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Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

Tranquada

2006

ChemInform

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Spin-Ordering Quantum Transitions of Superconductors in a Magnetic Field

Cited by 272 publications

References 18 publications

Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor

Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor

d-Wave superconductivity as a catalyst for antiferromagnetism in underdoped cuprates

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

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