Ultrafast Dynamics in High-Temperature Superconductors near a Quantum Critical Point
Final Report Abstract
During the project a methodology of ultrafast pump-probe spectroscopy has been developed and tested on a number of solid state systems. We could demonstrate that nonlinear optical spectroscopy can be performed on samples with lateral dimensions smaller than 100x100 µm2 up to pressures of 20 GPa. In particular, time-resolved measurements with probing in THz frequency range have been demonstrated for the first time. Potentially this methodology can be very useful for study of ultrafast dynamics of delocalized electrons in many materials which show pressure-induced insulator-metal transitions. Pump-probe spectroscopy measurements under pressure have discovered the following phenomena: (i) An unexpected slowing down of the relaxation dynamics in GaAs under pressure. This relaxation process related to the thermalization of the charge carriers photoexcited near the edge appears to be critically dependent on excess photon energy with respect to the pressuredependent band gap. Our results point out an important role of an electron-phonon scattering in this process. (ii) Pressure-induced melting of the charge-density wave order in CeTe3. In contrast to previous reports we unequivocally demonstrated that the CDW order is suppressed above 3.8 GPa. This process is accompanied by the divergence of the quasiparticle relaxation time and the disappearance of coherent phonon modes which are strongly coupled to the CDW order parameter. (iii) Metallization of VO2 at pressures above 6-8 GPa. The observed ultrafast dynamics drastically differs from the dynamics across the temperature-driven IMT in VO2. The observed behavior indicates a purely electronic pressure-induced Mott-Hubbard transition which is in contrast to thermally-induced IMT is not affected by the electron-phonon coupling (so-called Peierls mechanism). The results of the project demonstrate a high potential of ultrafast high-pressure pump-probe spectroscopy in the study of critical phenomena in correlated systems. In particular, the extension of the developed methodology towards low-temperature high-pressure conditions would open up a unique possibility to study quantum critical phenomena in high-temperature superconductors.
Publications
- Electric and magnetic terahertz nonlinearities resolved on the sub-cycle scale, New Journal of Physics 15, 065003 (2013)
A. Pashkin, A. Sell, T. Kampfrath, and R. Huber
(See online at https://doi.org/10.1088/1367-2630/15/6/065003) - Ultrafast dynamics in CeTe3 across the pressure-induced charge-density-wave transition, Workshop on Pressure and Strain Effects in Correlated Electron Materials, Dresden, Germany (October 6-10, 2014)
J. Tauch, H. Schäfer, M. Obergfell, J. Demsar, P. Giraldo, I. R. Fisher, and A. Pashkin
- Ultrafast dynamics in CeTe3 near the pressure-induced charge-density-wave transition, DPG Spring Meeting, Berlin, Germany (March 16-20, 2015)
J. Tauch, H. Schäfer, M. Obergfell, J. Demsar, P. Giraldo, I. R. Fisher, and A. Pashkin
- Ultrafast dynamics in the charge-density-wave material CeTe3 across the pressure-induced phase transition, Joint AIRAPT-25th & EHPRG-53rd International Conference on High Pressure Science and Technology, Madrid, Spain (August 30 – September 4, 2015)
J. Tauch, H. Schäfer, M. Obergfell, J. Demsar, P. Giraldo, I. R. Fisher, and A. Pashkin
- Ultrafast nonlinear response of GaAs under high pressures, Joint AIRAPT-25th & EHPRG-53rd International Conference on High Pressure Science and Technology, Madrid, Spain (August 30 – September 4, 2015)
J. M. Braun, H. Schneider, M. Helm, and A. Pashkin
- Ultrafast dynamics in VO2 under high pressures, 54th European High Pressure Research Group (EHPRG) International Meeting on High Pressure Science and Technology, Bayreuth, Germany (September 4 – 9, 2016)
J. M. Braun, H. Schneider, M. Helm, L. A. Boatner, R. E. Marvel, R. F. Haglund, and A. Pashkin
- Ultrafast nonlinear response of GaAs under high pressures, DPG Spring Meeting, Regensburg, Germany (March 6 – 11, 2016)
J. M. Braun, J. F. Schmidt, D. V. Seletskiy, H. Schneider, M. Helm, and A. Pashkin
