Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - Phonton (Phon(t)on-induced phase transitions)

Teaser

One of our dreams for the future is to control and manipulate complex materials and devices at will.This progress would revolutionize technology and influence many aspects of our everyday life. Apromising direction is the control of material properties by electromagnetic...

Summary

One of our dreams for the future is to control and manipulate complex materials and devices at will. This progress would revolutionize technology and influence many aspects of our everyday life. A promising direction is the control of material properties by electromagnetic radiation leading to photo- induced phase transitions. An example of such a transition is the reported dynamically induced superconductivity via a laser pulse. Whereas the theoretical description of the coupling of fermions to bosonic modes in equilibrium has seen enormous progress and explains highly non-trivial phenomena as the phonon-induced superconductivity, driven systems pose many puzzles. In addition to the inherent time-dependence of the external driving field, a multitude of possible excitation and relaxation mechanisms challenge the theoretical understanding. Recently in the field of quantum optics, a much cleaner realization of a photo-induced phase transition, the Dicke transition, has been observed for bosonic quantum gases loaded in an optical cavity. Above a critical pump strength of an external laser field, the ensemble undergoes a transition to an ordered phase. We aim to advance the general theoretical understanding of photo-induced phase transitions both in the field of solid state physics and quantum optics. In particular, we will focus on the design and investigation of photo-induced transitions to unconventional superconductivity and non-trivial topological phases. Our insights will be applied to fermonic quantum gases in optical cavities and solid state materials. In order to treat these systems efficiently, we will develop new variants of the numerical density matrix renormalization group (or also called matrix product state) methods and combine these with analytical approaches.

Work performed

So far, we have proposed an experimentally realistic setup in order to dynamically generate and stabilize non-trivial topological states. This setup uses a quantum gas coupled in a novel way to an optical resonator. By the novel coupling a cavity-assisted movement of the atoms occurs which leads to the topologically non-trivial phases. The topologically non-trivial state is stabilized by the dissipative attractor dynamics due to cavity losses.
Further, we design a setup which would enable the dynamic generation of superconducting and charge density wave states.
We find interesting dynamics, e.g. critical dynamics or aging, in dissipative systems signaled by two-time correlations functions.

Final results

We expect that we will design ways in order to generate and control dynamically complex states, such as unconventional superconductivity. We plan to investigate the dynamics and the stabilization of these states following different schemes of control.
These might be used in order to design materials with dynamically controllable functionalities which could lead to technical applications.