NOVEL MAGNETISM IN A MODEL CUPRATE SUPERCONDUCTOR
| Date/Time: | Thursday, 01 Sep 2011 - Saturday, 03 Sep 2011 |
|---|---|
| Location: | Room 5 PHYSICS |
| Phone: | 515-294-5630 |
| Channel: | College of Liberal Arts and Sciences |
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Magnetic correlations might cause the superconductivity in the cuprates and are generally believed to be antiferromagnetic. Following our success in growing sizable crystals of the structurally simple compound HgBa_2CuO_(4+delta) [1], we used polarized neutron diffraction to demonstrate the universal existence of a novel type of magnetic order in superconducting samples [2]. Unlike antiferromagnetism, this order does not break the lattice translational symmetry. Our inelastic neutron scattering measurements confirmed the existence of the well-known magnetic resonance at the antiferromagnetic point [3] and to led to the insight that the resonance energy is universally related to the superconducting gap in several families of unconventional superconductors [4]. These experiments also resulted in the discovery of several excitations branches that appear to be fundamental collective modes associated with the novel magnetic order [5]. This pseudogap magnetism is consistent with a particular type of order involving circulating charge currents and with the notion that the phase diagram of the cuprates is controlled by an underlying quantum critical point [6].
[1] X. Zhao et al., Adv. Mat. 18, 3243 (2006); N. Barišić et al., Phys. Rev. B 78, 054518 (2008).
[2] Y. Li et al., Nature 455, 372 (2008).
[3] G. Yu et al., Phys. Rev. B 81, 064518 (2010).
[4] G. Yu et al., Nature Physics 5, 873 (2009).
[5] Y. Li et al., Nature 468, 283 (2010) and unpublished results.
[6] C. Varma, Nature 468, 184 (2010).