Superstripes

Superstripes is a generic name for a phase with spatial broken symmetry that favors the onset of superconducting or superfluid quantum order. This scenario emerged in the 1990s when no-homogeneous metallic heterostructures at the atomic limit with a broken spatial symmetry have been found to favor superconductivity. [1][2] Before a broken spatial symmetry was expected to compete and suppress the superconducting order. The driving mechanism for the amplification of the superconductivity critical temperature in superstripes matter has been proposed to be the shape resonance in the energy gap parameters ∆n that is a type of Fano resonance for coexisting condensates. [3][4] The superstripes show multigap superconductivity near a 2.5 Lifshitz transition where the renormalization of chemical potential at the metal-to-superconductor transition is not negligeable and the self-consistent solution of the gaps equation is required. The superstripes lattice scenario is made of puddles of multigap superstripes matter forming a superconducting network where different gaps are not only different in different portions of the k-space but also in different portions of the real space with a complex scale free distribution of Josephson junctions.

A popular web page on superstripes is www.superstripes.com

History

The name SUPERSTRIPES was introduced in 2000 at the international conference on "Stripes and High Tc Superconductivity" held in Rome University to describe the particular phase of matter where a broken symmetry appearing at a transition from a phase with higher dimensionality N (3D or 2D) to a phase with lower dimensionality N-1 (2D or 1D) favors the superconducting or superfluid phase and it could increase the normal to superconducting transition temperature with the possible emergence of High-temperature superconductivity. The name SUPERSTRIPES scenario was introduced to make the key difference with the STRIPES scenario where the phase transition from a phase with higher dimensionality N (like a 2D electron gas) to the phase with broken symmetry and lower dimensionality N-1 (like a quasi 1D striped fluid) competes and suppresses the transition temperature to the superfluid phase and favors modulated striped magnetic ordering. In the broken symmetry of superstripes phase the structural modulation coexists and favors high temperature superconductivity [1]

High temperature superconductivity in heterostructures at atomic limit

The prediction of high temperature superconductivity transition temperatures is rightly considered to be one of the most difficult problems in theoretical physics. The problem remained elusive for many years since these materials have generally a very complex structure making unuseful theoretical modelling for a homogeneous system. The advances in experimental investigation on local lattice fluctuations have driven the community to the conclusion that it is a problem of quantum physics in complex matter. A growing paradigm for High Temperature Superconductivity in Superstripes is that a key term is the quantum interference effect between pairing channels, i.e., a resonance in the exchange-like, Josephson-like pair transfer term between different condensates. The quantum configuration interaction between different pairing channels is a particular case of shape resonance belonging to the group of Fano Feshbach resonances in atomic and nuclear physics. The critical temperature shows a suppression, due to a Fano antiresonance, when the chemical potential is tuned at a band edge where a new Fermi surface spot appears i.e., an "electronic topological transition" (ETT) or 2.5 Lifshitz transition or, a metal-to-metal topological transition. The Tc amplification is switched on when the chemical potential is tuned above the band edge in an energy region away from the band edge of the order of 1 or 2 times the energy cut off of the pairing interaction. The Tc is further amplified at the shape resonace if in this range the Fermi surface of the appearing fermi surface spot changes its dimensionality (for example the Lifshitz transition for openign a neck in a tubular Fermi surface). [5] The tuning of the chemical potential at the shape resonance can be obtained by changing: the charge density and/or the superlattice structural parameters, and/or the superlattice misfit strain and/or the disorder. Direct evidence for shape resonances in superstripes matter is provided by the anomalous variation of the isotope effect on the critical temperature by tuning the chemical potential as shown by: Perali, A., Innocenti, D., Valletta, A. & Bianconi, A. Anomalous isotope effect near a 2.5 lifshitz transition in a multi-band multi-condensate superconductor made of a superlattice of stripes. Superconductor Science and Technology 25, 124002 (2012).

Materials

It was known that the high temperature cuprate superconductors have a complex lattice structure.[6][7][8][9][10][11][12] In 1993 it was proposed [13] that these materials belong to a particular class of materials called Heterostructures at atomic limit made of a superlattice of superconducting atomic layers intercalated by a different material with the role of spacer.

All new high temperature superconducting materials discovered in the years 2001-2013 are heterostructures at atomic limit made of the active atomic layers: honeycomb boron layer in diborides, graphene in intercalated graphite, CoO2 atomic bbc monolayers in cobaltates, FeAs atomic fluorite monolayers in pnictides, FeSe atomic fluorite monolayers in selenides.

In these materials the joint effect of (a) increasing the lattice misfit strain to a critical value, and (b) tuning the chemical potential near a Lifshitz transition in presence of electron-electron interactions induce a lattice instability with formation of the network of superconducting striped puddles in an insulating or metallic background.

This complex scenario has been called "superstripes scenario" where the 2D atomic layers show functional lattice inhomogeneities: "Ripples puddles" of local lattice distortion have been observed in La2CuO4+y [14][15] in Bi222 ; striped puddles of ordered dopants in the spacer layers have been seen in superoxygenated La2CuO4 [16] and in YBaCuO [17] The network of superconducting striped puddles has been found also in MFeAs pnictides [18] and recently in KFeSe selenides [19]

The lattice defects self organization can be controlled by strain engineering [20] and photoinduced effects [21]

Superstripes conferences

"Superstripes" is the name of a series of workshops and conferences that started in 2008:[22] FeAs High Tc Superconducting Multilayers and Related Phenomena: Roma 9–13 December 2008 chaired by Antonio Bianconi

Superstripes 2010 Quantum Phenomena in Complex Matter, Erice, Italy, July 19–25, 2010 chaired by Antonio Bianconi and Giorgio Benedek

Superstripes 2012 Phase Separation and superstripes in high temperature superconductors and related materials, Erice – Italy, July 11–17, 2012 Chaired by Antonio Bianconi and Giorgio Benedek

Superstripes 2013 International conference on "QUANTUM IN COMPLEX MATTER" :Superconductivity, Magnetism and Ferroelectricity Ischia, Naple, Italy May 27 - June 1, 2013 Chairman Prof. Antonio Bianconi. This is a recognized EPS conference sponsored by European Physical Society "Superstripes 2013"

References

  1. ↑ 1.0 1.1 Bianconi, A. Superstripes International Journal of Modern Physics B 14, 3289-3297 (2000). doi:10.1142/S0217979200003769.
  2. ↑ Bianconi, A., Di Castro, D., Saini, N. L. & Bianconi, G. Superstripes (self organization of quantum wires in high Tc superconductors). In Thorpe, M. F. & Phillips, J. C. (eds.) Phase Transitions and Self-Organization in Electronic and Molecular Networks, Fundamental Materials Research, chap. 24, 375-388 (Kluwer Academic Publishers, Boston, 2002). doi:10.1007/0-306-47113-2_24.
  3. ↑ Perali, A. et al., The gap amplification at a shape resonance in a superlattice of quantum stripes: A mechanism for high Tc Solid State Communications 100, 181-186 (1996).
  4. ↑ Bianconi, A., Valletta, A., Perali, A. & Saini, N. L. Superconductivity of a striped phase at the atomic limit Physica C: Superconductivity 296, 269-280 (1998).
  5. ↑ D. innocenti et al. Resonant and crossover phenomena in a multiband superconductor: Tuning the chemical potential near a band edge. Physical Review B 82, 184528 (2010).{{doi:10.1103/physrevb.82.184528}}.
  6. ↑ Müller, K. A. From phase separation to stripes In Bianconi, A. & Saini, N. L. (eds.) Stripes and Related Phenomena, pages 1-8 (Kluwer Academic/Plenum Publishers, New York, 2002)..
  7. ↑ Müller, K. A. Essential Heterogeneities in Hole-Doped Cuprate Superconductors, vol. 114/2005 of Structure & Bonding, 1-11 (Springer, Berlin / Heidelberg, 2005). URL http://dx.doi.org/10.1007/b101015
  8. ↑ Raveau, B. The perovskite history: More than 60 years of research from the discovery of ferroelectricity to colossal magnetoresistance via high Tc superconductivity. Progress in Solid State Chemistry 35, 171-173 (2007). URL http://dx.doi.org/10.1016/j.progsolidstchem.2007.04.001.
  9. ↑ Bishop, A. R. High Tc oxides: a collusion of spin, charge and lattice. Journal of Physics: Conference Series 108, 012027+ (2008). doi:10.1088/1742-6596/108/1/012027
  10. ↑ Stripes and related phenomena, edited by Antonio Bianconi and Naurang L. Saini Published in 2000, Kluwer Academic/Plenum Publishers (New York) ISBN 0-306-46419-5
  11. ↑ Symmetry and Heterogeneity in High Temperature Superconductors (NATO Science Series II: Mathematics, Physics & Chemistry)] ISNB: 9781402039881, by Antonio Bianconi (Editor) Springer
  12. ↑ Superconductivity in Complex Systems, edited by K. Alex Müller and Annette Bussmann-Holder, Book Series Structure & Bonding, Publisher Springer Berlin / Heidelberg ISBN 978-3-540-23124-0
  13. ↑ Bianconi, A. On the possibility of new high Tc superconductors by producing metal heterostructures as in the cuprate perovskites Solid State Communications 89, 933-936 (1994).
  14. ↑ Di Castro, D., Colapietro, M. & Bianconi, G. Metallic stripes in oxygen doped La2CuO4.1 Int. J. Mod. Phys. 14, 3438-3443 (2000). doi:10.1142/S0217979200003927
  15. ↑ Poccia, N. et al. Optimum inhomogeneity of local lattice distortions in La2CuO4+y. Proceedings of the National Academy of Sciences 109, 15685-15690 (2012). URL http://dx.doi.org/10.1073/pnas.1208492109
  16. ↑ Fratini, M. et al. Scale-free structural organization of oxygen interstitials in La2CuO4+y. Nature 466, 841-844 (2010). URL http://dx.doi.org/10.1038/nature09260.
  17. ↑ Campi, G. et al. Scanning micro-x-ray diffraction unveils the distribution of oxygen chain nanoscale puddles in YBa$_2$Cu$_3$O$_6.33$. Physical Review B 87, 014517+ (2013) URL http://dx.doi.org/10.1103/physrevb.87.014517
  18. ↑ Caivano, R. et al. Feshbach resonance and mesoscopic phase separation near a quantum critical point in multiband FeAs-based superconductors. Superconductor Science and Technology 22, 014004+ (2009). URL http://dx.doi.org/10.1088/0953-2048/22/1/014004.
  19. ↑ Ricci, A. et al. Nanoscale phase separation in the iron chalcogenide superconductor k$_0.8$fe$_1.6$se$_2$ as seen via scanning nanofocused x-ray diffraction. Physical Review B 84, 060511+ (2011). URL http://dx.doi.org/10.1103/physrevb.84.060511
  20. ↑ S. Agrestini, N. L. Saini, G. Bianconi, and A. Bianconi, Journal of Physics A: Mathematical and General 36, 9133 (2003), URL http://dx.doi.org/10.1088/0305-4470/36/35/302.
  21. ↑ Poccia, N. et al. Evolution and control of oxygen order in a cuprate superconductor. Nat Mater 10, 733-736 (2011). URL http://dx.doi.org/10.1038/nmat3088.
  22. ↑ Superstripes 2008

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