Highlights

X-ray diffraction has revealed structural modifications in high-temperature superconductors induced by  femtosecond pulses of THz radiation, which appear to be responsible for transient superconductivity far above the equilibrium transition temperature. The results were published in Nature.

Ultrafast structural modifications in a high-temperature superconductor

X-ray diffraction has revealed structural modifications in high-temperature superconductors induced by  femtosecond pulses of THz radiation, which appear to be responsible for transient superconductivity far above the equilibrium transition temperature. The results were published in Nature.
Experiments performed in collaboration with Andrea Cavalleri's group at the MPI in Hamburg revealed coherent transport phenomena strikingly similar to superconductivity when underdoped cuprate single crystals are illuminated by pulsed Terahertz light fields at room temperature.

Optically enhanced coherent transport at room temperature in an underdoped cuprate

Experiments performed in collaboration with Andrea Cavalleri's group at the MPI in Hamburg revealed coherent transport phenomena strikingly similar to superconductivity when underdoped cuprate single crystals are illuminated by pulsed Terahertz light fields at room temperature.
Two new papers in Science highlight the ubiquitous interplay between charge density waves and high-temperature superconductivity, and its influence on the well known "Fermi arc" phenomenon in underdoped copper oxide superconductors.

Superconducting cuprates

Two new papers in Science highlight the ubiquitous interplay between charge density waves and high-temperature superconductivity, and its influence on the well known "Fermi arc" phenomenon in underdoped copper oxide superconductors.
Resonant x-ray scattering experiments on highly ordered 'Ortho-II' YBa2Cu3O6.55 and Zn-substituted YBa2Cu3O6.6 revealed a three-phase competition between spin-modulated,charge-modulated, and superconducting states in underdoped cuprate superconductors. S. Blanco Canosa et al., Phys. Rev. Lett. 2013

Three-phase competition in underdoped YBa2Cu3O6+x

Resonant x-ray scattering experiments on highly ordered 'Ortho-II' YBa2Cu3O6.55 and Zn-substituted YBa2Cu3O6.6 revealed a three-phase competition between spin-modulated,charge-modulated, and superconducting states in underdoped cuprate superconductors. S. Blanco Canosa et al., Phys. Rev. Lett. 2013
Using resonant x-ray scattering we obtained the unambiguous evidence for long-range incommensurate charge-density-wave fluctuations competing with superconductivity in underdoped (Y,Nd)Ba2Cu3O6+x. G. Ghiringhelli et al., Science, 2012

A density-wave order that competes with superconductivity

Using resonant x-ray scattering we obtained the unambiguous evidence for long-range incommensurate charge-density-wave fluctuations competing with superconductivity in underdoped (Y,Nd)Ba2Cu3O6+x. G. Ghiringhelli et al., Science, 2012

Magnetic resonant mode in the Rb2Fe4Se5 superconductor

A resonant magnetic excitation in the Rb-245 iron-selenide superconductor has been discovered at a wave vector, which differs from the ones characterizing magnetic resonant modes in other iron-based superconductors. J. T. Park et al. Phys. Rev. Lett., 2011 G. Friemel et al. Phys. Rev. B (R), 2012

Unconventional Superconductivity

The microscopic description of novel superconductivity states in complex materials such as layered copper oxides and iron pnictides is one of the most important challenges in current solid-state physics. Our group uses high-quality single crystals and state-of-the-art experimental methods to derive accurate spectra of spin and charge excitations in these materials. Such data are essential to motivate and test new theoretical concepts for the correlated electron systems that support unconventional superconductivity.

YBa2Cu3O7 crystal array for neutron scattering

YBa2Cu3O7 crystal array for neutron scattering

Recent focus and key Publications

Cuprates

High Temperature Superconductivity in the Cuprates

B. Keimer, S. A. Kivelson, M. R. Norman, S. Uchida, J. Zaanen.
arxiv.org 1409.4673

Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5

R. Mankowsky, A. Subedi, M. Först, S. O. Mariager, M. Chollet, H. T. Lemke, J. S. Robinson, J. M. Glownia, M. P. Minitti, A. Frano, M. Fechner, N. A. Spaldin, T. Loew, B. Keimer, A. Georges & A. Cavalleri.
Nature Materials, published 04. Dec 2014

Optically enhanced coherent transport in YBa2Cu3O6.5 by ultrafast redistribution of interlayer coupling

W. Hu, S. Kaiser, D. Nicoletti, C. R. Hunt, I. Gierz, M. C. Hoffmann, M. Le Tacon, T. Loew, B. Keimer & A. Cavalleri
Nature Materials, published 11. May 2014

Ubiquitous Interplay Between Charge Ordering and High-Temperature Superconductivity in Cuprates

E. H. da Silva Neto, P. Aynajian, A. Frano, R. Comin, E. Schierle, E. Weschke, A. Gyenis, J. Wen, J. Schneeloch, Z. Xu, S. Ono, G. Gu, M. Le Tacon, A. Yazdani.
Science Vol. 343 no. 6169 pp. 393-396, published 24. January 2014

Charge Order Driven by Fermi-Arc Instability in Bi2Sr2−xLaxCuO6+δ
R. Comin, A. Frano, M. M. Yee, Y. Yoshida, H. Eisaki, E. Schierle, E. Weschke, R. Sutarto, F. He, A. Soumyanarayanan, Yang He, M. Le Tacon, I. S. Elfimov, Jennifer E. Hoffman, G. A. Sawatzky, B. Keimer, A. Damascelli.
Science Vol. 343 no.6169 pp. 390-392, published 24. January 2014

Momentum-Dependent Charge Correlations in Three-phase competition in YBa2Cu3O6+δ Superconductors Probey by Resonant X-Ray Scattering: Evidence for Three Competing Phases
S. Blanco-Canosa, A. Frano, T. Loew, Y. Lu, J. Porras, G. Ghiringhelli, M. Minola, C. Mazzoli, L. Braicovich, E. Schierle, E. Weschke, M. Le Tacon, B. Keimer.
Phys. Rev. Lett. 110 (2013) 187001; published 3 Mai 2013.

Feedback effect on high-energy magnetic fluctuations in the model high-temperature superconductor HgBa2CuO4 + δ observed by electronic Raman scattering
Yuan Li, M. Le Tacon, M. Bakr, D. Terrade, D. Manske, R. Hackl, L. Ji, M. K. Chan, N. Barišić, X. Zhao, M. Greven, B. Keimer.
Phys. Rev. Lett. 108 (2012), 227003; published 31 May 2012.

Distinct Charge Orders in the Planes and Chains of Ortho-III-Ordered YBa2Cu3O6+δ Superconductors Identified by Resonant Elastic X-ray Scattering
A. J. Achkar, R. Sutarto, X. Mao, F. He, A. Frañó, S. Blanco-Canosa, M. Le Tacon, G. Ghiringhelli, L. Braicovich, M. Minola, M. Moretti Sala, C. Mazzoli, R. Liang, D. A. Bonn, W. N. Hardy, B. Keimer, G. A. Sawatzky, and D. G. Hawthorn.
Phys. Rev. Lett. 109 (2012) 167001; published 17 October 2012.

Long-range incommensurate charge fluctuations in (Y,Nd)Ba2Cu3O6+x
G. Ghiringhelli, M. Le Tacon, M. Minola, S. Blanco-Canosa, C. Mazzoli, N. B. Brookes, G. M. De Luca, A. Frañó, D. G. Hawthorn, F. He, T. Loew, M. Moretti Sala, D. C. Peets, M. Salluzzo, E. Schierle, R. Sutarto, G. A. Sawatzky, E. Weschke, B. Keimer, L. Braicovich.
Science 337 (2012), 821−825; published 17 August 2012.

Iron pnictides

Spin-state crossover model for the magnetism of iron pnictides
J. Chaloupka, G. Khaliullin.
Phys. Rev. Lett. 110 (2013) 207205; published 14 May 2013.

Nanoscale layering of antiferromagnetic and superconducting phases in Rb2Fe4Se5
A. Charnukha, A. Cvitkovic, T. Prokscha, D. Pröpper, N. Ocelic, A. Suter, Z. Salman, E. Morenzoni, J. Deisenhofer, V. Tsurkan, A. Loidl, B. Keimer, A. V. Boris.
Phys. Rev. Lett. 109 (2012), 017003; published 5 July 2012.

Reciprocal-space structure and dispersion of the magnetic resonant mode in the superconducting phase of RbxFe2−ySe2 single crystals
G. Friemel, J. T. Park, T. A. Maier, V. Tsurkan, Yuan Li, J. Deisenhofer, H.-A. Krug von Nidda, A. Loidl, A. Ivanov, B. Keimer, D. S. Inosov.
Phys. Rev. B 85 (2012), 140511(R); published 20 April 2012.

Superconductivity-induced optical anomaly in an iron arsenide
A. Charnukha, P. Popovich, Y. Matiks, D. L. Sun, C. T. Lin, A. N. Yaresko, B. Keimer, A. V. Boris.
Nature Communications 2 (2011), 219; published 1 March 2011.

Magnetic resonant mode in the low-energy spin-excitation spectrum of superconducting Rb2Fe4Se5 single crystals
J. T. Park, G. Friemel, Yuan Li, J.-H. Kim, V. Tsurkan, J. Deisenhofer, H.-A. Krug von Nidda, A. Loidl, A. Ivanov, B. Keimer, D. S. Inosov.
Phys. Rev. Lett. 107 (2011), 177005; published 19 October 2011.

Eliashberg approach to infrared anomalies induced by the superconducting state of Ba0.68K0.32Fe2As2 single crystals
A. Charnukha, O. V. Dolgov, A. A. Golubov, Y. Matiks, D. L. Sun, C. T. Lin, B. Keimer, A. V. Boris.
Phys. Rev. B 84 (2011), 174511; published 18 November 2011.

Normal-state spin dynamics and temperature-dependent spin-resonance energy in optimally doped BaFe1.85Co0.15As2
D. S. Inosov, J. T. Park, P. Bourges, D. L. Sun, Y. Sidis, A. Schneidewind, K. Hradil, D. Haug, C. T. Lin, B. Keimer, V. Hinkov.
Nature Physics 6 (2010), 178–181; published 1 March 2010.
Supplementary information

 
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