Abstract
Photoinduced phase transitions have become a very important field of study with the advent of diverse time-resolved experimental techniques whose time resolution matches the electron, lattice, and spin relaxation dynamics associated with elementary excitations in quantum materials. Most techniques currently available rely on stroboscopic data-averaging over multiple transition outcomes. However, each time a transition takes place, fluctuations close to the time of the transition ensure that the phase transition outcome is different, with the emergence of different topological defect textures. In this paper, we briefly review the non-perturbative processes in selected charge-ordered quantum systems and the methods for their observation with different time-resolved techniques and scanning tunneling microscopy, which avoids the problem of averaging. The topological defect dynamics are seen to play an essential role in stabilizing emergent states in non-equilibrium transitions, appearing on different timescales as well as determining the emergent properties of the system. The phenomena are fundamentally important for understanding the fabric of matter in the Universe, as well as for possible applications in non-volatile memory devices.
Highlights
Recent progress in time-domain techniques has made it possible to study the dynamics of elementary excitations under different non-equilibrium conditions and whence the appearance of emergent order in real time [1,2,3,4,5] With low laser excitation intensities, the system is perturbed only slightly out of equilibrium, and the response is comparable to the information that one can obtain from frequency domain spectroscopies
Different excitations can be directly distinguished by their respective lifetimes, so with different probes very detailed information can be obtained on the system dynamics near equilibrium in many different materials, strongly correlated superconductors being perhaps the most researched
Since the lateral dimensions of the beam (100 um) are large compared with the depth (20–100 nm), the main effect is the formation of domains parallel to the surface
Summary
Recent progress in time-domain techniques has made it possible to study the dynamics of elementary excitations under different non-equilibrium conditions and whence the appearance of emergent order in real time [1,2,3,4,5] With low laser excitation intensities, the system is perturbed only slightly out of equilibrium, and the response is comparable to the information that one can obtain from frequency domain spectroscopies (the perturbative, or weak excitation regime). The field of topological states emerging through non-equilibrium transitions has gained wider importance because ultrafast switching between different electronically ordered states can be used to store information, leading to ultra-low energy non-volatile ultrafast memory devices for which there is currently a great need. The search using ultrafast techniques for better and more convenient materials and systems is imperative, stimulating further research in the field
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