Abstract-2D THz spectroscopic investigation of ballistic conduction-band electron dynamics in InSb

S.Houver, L. Huber, M. Savoini, E. Abreu, S. L. Johnson

https://arxiv.org/abs/1901.00691

Using reflective cross-polarized 2D THz time-domain spectroscopy in the range of 1-12 THz, we follow the trajectory of the out-of-equilibrium electron population in the low-bandgap semiconductor InSb. The 2D THz spectra show a set of distinct features at combinations of the plasma-edge and vibration frequencies. Using finite difference time domain simulations combined with a tight binding model of the band structure, we assign these features to electronic nonlinearities and show that the nonlinear response in the first picoseconds is dominated by coherent ballistic motion of the electrons. We demonstrate that this technique can be used to investigate the landscape of the band curvature near the Gamma-point as illustrated by the observation of anisotropy in the (100)-plane.

Abstract-Coherent phonon spectroscopy of non-fully symmetric modes using resonant terahertz excitation

T. Huber^1,a), M. Ranke², A. Ferrer^1,3, L. Huber¹ and S. L. Johnson¹
http://scitation.aip.org/content/aip/journal/apl/107/9/10.1063/1.4930021
1 Institute for Quantum Electronics, Physics Department, ETH Zurich, CH-8093 Zurich, Switzerland
2 The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany
3 Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
a) Electronic mail: tihuber@phys.ethz.ch
Appl. Phys. Lett. 107, 091107 (2015); http://dx.doi.org/10.1063/1.4930021

We use intense terahertz (THz) frequency electromagnetic pulses generated via optical rectification in an organic crystal to drive vibrational lattice modes in single crystal Tellurium. The coherent modes are detected by measuring the polarization changes of femtosecond laser pulses reflecting from the sample surface, resulting in a phase-resolved detection of the coherent lattice motion. We compare the data to a model of Lorentz oscillators driven by the near-single-cycle broadband THz pulse. The demonstrated technique of optically probed coherent phonon spectroscopy with THz frequency excitation could prove to be a viable alternative to other time-resolved spectroscopic methods like standard THz time domainspectroscopy.

Abstract-Large-Amplitude Spin Dynamics Driven by a THz Pulse in Resonance with an Electromagnon

1. T. Kubacka1,*, 
2. J. A. Johnson2, 
3. M. C. Hoffmann3, 
4. C. Vicario4, 
5. S. de Jong3, 
6. P. Beaud2, 
7. S. Grübel2, 
8. S.-W. Huang2,
9. L. Huber1, 
10. L. Patthey4, 
11. Y.-D. Chuang5, 
12. J. J. Turner3, 
13. G. L. Dakovski3, 
14. W.-S. Lee3, 
15. M. P. Minitti3, 
16. W. Schlotter3,
17. R. G. Moore6, 
18. C. P. Hauri4,7, 
19. S. M. Koohpayeh8, 
20. V. Scagnoli2, 
21. G. Ingold2, 
22. S. L. Johnson1, 
23. U. Staub2

-Author Affiliations

1. ¹ETH Zurich, Institute for Quantum Electronics, Wolfgang-Pauli-Strasse 16, 8093 Zurich, Switzerland.
2. ²Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
3. ³Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA94025, USA.
4. ⁴SwissFEL, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
5. ⁵Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
6. ⁶Stanford Institute for Materials and Energy Sciences (SIMES), SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
7. ⁷Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland.
8. ⁸Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.

1. ↵*Corresponding author. E-mail: tkubacka@phys.ethz.ch
2. http://www.sciencemag.org/content/early/2014/03/05/science.1242862

Multiferroics have attracted strong interest for potential applications where electric fields control magnetic order. The ultimate speed of control via magnetoelectric coupling, however, remains largely unexplored. Here, we report on an experiment in which we drive spin dynamics in multiferroic TbMnO₃ with an intense few-cycle terahertz (THz) light pulse tuned to resonance with an electromagnon, an electric-dipole active spin excitation_.We observe the resulting spin motion using time-resolved resonant soft x-ray diffraction. Our results show that it is possible to directly manipulate atomic-scale magnetic structures using the electric field of light on a sub-picosecond timescale.