Low Energy Electrodynamics in Solids 2012

Towards understanding the c-axis infrared response of underdoped cuprate superconductors

24 Jul 2012, 20:00

2h

Fountain Court (Embassy Suites Napa Valley)

Board: 78

Poster High-Tc Cuprates Poster Session 2

Speaker

Dominik Munzar (Masaryk University)

Description

Dominik Munzar and Jiri Vasatko, Department of Condensed Matter Physics, Faculty of Science, and Central European Institute of Technology, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic The c-axis infrared (IR) conductivity of underdoped high-Tc cuprate superconductors reveals a pronounced pseudogap (PG) and, for materials with two CuO2 planes per unit cell, signatures of coherent electronic coupling within the pair of closely spaced planes, in particular the so-called transverse plasma mode (TPM) located around 400 cm-1. The PG develops below T* much greater than Tc, the TPM below Tons, Tc less than Tons much less than T*. We report on results of our recent studies aiming at understanding these phenomena. (a) The formulas frequently used to describe the c-axis response of the coupled electron-phonon system of bilayer cuprate superconductors, that were originally obtained at the level of the phenomenological multilayer model (MLM), have been derived by using diagrammatic perturbation theory [1,2]. This provides a support for several important findings based thereon, in particular those of [3]. (b) The reported magnetic field (H perpendicular to the planes) induced changes of the TPM [4,3] have been clarified using the MLM [5]. Results of our analysis suggest that the response at H=0 and T=Tc is close to that at H = ca 25 T less than Hc2 and T much less than Tc, in accord with theories attributing the above Tc state to that of a superconductor lacking the long range phase coherence. (c) The qualitative difference between the manifestations of the PG in the c-axis IR response and those in the in-plane one belongs to major unsolved problems in the physics of the cuprates. In the third part of our contribution, implications of the MIR data reported by Yu et al. [6] will be discussed. [1] J. Chaloupka, C. Bernhard, D. Munzar, Phys. Rev. B 79, 184513 (2009). [2] J. Vasatko and D. Munzar, submitted to Phys. Rev. B, cond-mat 1203.6523v1. [3] A. Dubroka et al., Phys. Rev. Lett. 106, 047006 (2011). [4] A. D. LaForge et al., Phys. Rev. B 76, 054524 (2007). [5] J. Marek and D. Munzar, Journ. of Phys.: Condensed Matter 23, 415703 (2011). [6] L. Yu et al., Phys. Rev. Lett. 100, 177004 (2008).