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Dr. Denis Golež (IJS, FMF): Stabilizing the excitonic condensate

Date of publication: 10. 2. 2022
Monday physics colloquium
Monday
14
February
Time:
16:15 - 17:15
Location:
Zoom
ID: 980 0889 5298
V ponedeljek, 14. 2. 2022, ob 16:15 prek Zooma

Bose-Einstein condensate is one of the most fascinating states of matter, where quantum effects become apparent on macroscopic scales. The phenomenon was first realized with atoms at low temperatures requiring sophisticated cooling techniques. A strategy to increase the critical temperature is to use much lighter (quasi-)particles, and I will present solid-state platforms harnessing this idea using bound pairs of electrons and holes called excitons.
The first platform is based on carefully designed nanodevices with two atomically thin layers of semiconductors separated by an insulating layer. We have shown that such a system can exhibit a second-order Josephson effect with two degenerate ground states. An electric pulse can switch between the two states, and the system can be used as an ultrafast switch. The second class of platforms employs low-dimensional solids (transition metal chalcogenides) close to the semiconductor-semimetal transition. In these systems, the challenge is to understand the competition between the excitonic phase and other degrees of freedom, like lattice excitations. We proposed a nonlinear optical protocol based on pump-probe spectroscopy to quantify the competition. Inspired by the proposal, optical experiments on the candidate material Ta2NiSe5 indeed show the stability of excitonic condensation and how this opens new avenues for the dissipationless transfer of energy.

https://uni-lj-si.zoom.us/j/98008895298