Coherent Optical Phononics
OPEN ACCESS
Author / Producer
Date
2018-12-13
Publication Type
Doctoral Thesis
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
In my thesis, I have strengthened the understanding of the vibrational dynamics of materials in response to stimulation by intense laser pulses. Vibrations of the crystal structure can be used to manipulate a material's properties in the electronic ground state on timescales less than a picosecond by changing the average ionic lattice that the electrons experience. In order to leverage this technique, the quantized vibrations of the lattice, called optical phonons, have to be excited coherently by intense pulses in the terahertz and mid-infrared spectral region.
Excitation mechanisms for optical phonons have been investigated theoretically on a phenomenological level for several decades, but due to the high computational costs, a quantitative description within the density functional theory framework has only become possible in recent years. I further developed and used this toolkit to explain experimental discoveries that were not previously understood and to predict new phenomena arising from coherent optical phonon excitation.
Here, I present three major research projects that I have completed on this topic: In the first project, I proposed a novel nonlinear phonon coupling mechanism that enhances the controllability over structural distortions induced in the crystal lattice. In the second project, I created a general framework that captures the different stimulated Raman scattering mechanisms for the excitation of Raman-active phonons in insulators. In particular, I proposed a novel scattering mechanism that significantly increases the efficiency of the excitation over established methods. In the third project I showed that magnetism arises from temporally varying electric polarization. I have demonstrated this phenomenon with the example of circularly polarized phonons that produce a magnetic moment, which interacts with an external magnetic field or the magnetic order of the material itself.
I conclude the thesis by giving a perspective for future research directions. I suggest that new discoveries in the field will be led by experiments carried out at free-electron laser facilities and by developments in the first-principles description of coupled electron- and spin-phonon dynamics. Understanding the time-dependent physics of phonons may in turn lead to new paradigms in designing materials with greater functionality in the static case.
Permanent link
Publication status
published
External links
Editor
Contributors
Examiner : Spaldin, Nicola
Examiner : Gambardella, Pietro
Examiner : Johnson, Steven L.
Book title
Journal / series
Volume
Pages / Article No.
Publisher
ETH Zurich
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Nonlinear phononics; Terahertz; Multiferroics
Organisational unit
03903 - Spaldin, Nicola A. / Spaldin, Nicola A.
Notes
Funding
Related publications and datasets
Is compiled by: http://hdl.handle.net/20.500.11850/128822
Is compiled by: http://hdl.handle.net/20.500.11850/209708
Is compiled by: http://hdl.handle.net/20.500.11850/190352
Is compiled by: http://hdl.handle.net/20.500.11850/267638