It is well-known that the symmetry of the nonlinear optical susceptibility is strongly affected by a magnetization or an external applied magnetic field. Thus it is of considerable interest to extend the symmetry analysis of the nonlinear magneto-optical response to the superconducting state for different symmetries of the superconducting order parameter. A symmetry dependent contribution to the magneto-optical response without tunneling contact results in optical second harmonic generation. Although it is, due to the gauge invariance, impossible to measure the phase of the superconducting order parameter without tunneling contact, it is still possible to measure its symmetry, not solely its magnitude. Due to the surface sensitivity of nonlinear optics for systems with bulk inversion symmetry, one can take advantage of the broken inversion symmetry at the surface. This is of interest, because Cooper pairing, together with the always present spin-orbit coupling, is then no more purely singlet- or triplet-like. The interference of the singlet and triplet pairing states, which is linear in spin-orbit interaction, leads to the symmetry sensitive contribution of the nonlinear optical response for systems in an external magnetic field. Can anyone illuminate me more about this?
Zero field muon measurements as a function of temperature show this effect rather clearly.
Zero field muon measurements as a function of temperature show this effect rather clearly.
I wish to remind the participants of the discussion that MOKE is a relatively inexpensive technique which any small laboratory can afford. So it is worth doing such experiments at home before one goes to a more expensive large neutron or muon facilities.
Recently J. Schmalian and W. Hu ̈bner have reported their results concerning the symmetry dependence of the non-linear magneto-optical response of s- and d-wave superconductors and discussed in detail the differences of the line shapes of the optical spectra. They find that it is possible to discriminate between an isotropic s-wave, a sx2+y2 - or dx2−y2- wave and a dxy- wave. However, no symmetry dependent differences between the sx2+y2- and the dx2−y2- waves occur, which are actually the most discussed symmetries of the high-Tc systems. Nevertheless nonlinear magneto-optics is shown to be an alternative and complementary method to gain insight into the symmetry of the superconducting gap function.
Thanks at last for some discussion!
Sure, muon spectroscopy is a poweful technique and can sometimes be obtained as a byproduct (almost) of the plused neutron facilities. Still not very cheap. Definitely not as cheap as a MOKE setup.
I highligted the superconductvity study. But MOKE microscopy is a very powerful tool for studing magnetic domains. This particular aspect interests me very much indeed.
You write that "the audience that can comment specifically on your question about MOKE + SC is very small, though" surprises me a bit. It may be true for SC though but surely MOKE is very much used by a large number of researchers (including those from India and Chiana) engaged in preparing and studying magnetic thin films and multilayers. Many of these laboratories must be having MOKE setup because that is cheapest tool to characterize these technologically important materials. Many of them have virtually no access to expensive facilities like ILL, ISIS, PSI, FRM II etc. etc. You talked before about polarized neutrons. Do you how limited these polarized neutron facilities are! Surely they are powerful but how nany can get access to these? When you have lab where you produce a hell of lot of thin films and multilayers you you wish to characterize and investigate them immediately and not wait to write an ILL research proposal (twice a year) and wait for the mercy of the subcommittee members. Even if everything goes through you may find during the experiment that your sample does not scatter neutrons as much as you have wished.
Mind that many great discoveries in condensed mattter science were done in a small laboratory and not in large facilities you are apparently so proud of.
I looked at your JMMM paper. So you were not investigating energy materials in Germany but used MOKE to study magnetic thin films and multilayers. I admit you cannot do much with MOKE with your energy materials.
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