Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 51: Nonequilibrium Quantum Many-Body Systems I (joint session TT/DY)
TT 51.1: Hauptvortrag
Mittwoch, 14. März 2018, 09:30–10:00, H 3010
Electronic Squeezing of Pumped Phonons: Negative U and Transient Superconductivity — •Dante M. Kennes1, Eli Y. Wilner1, David R. Reichman2, and Andrew J. Millis1 — 1Department of Physics, Columbia University, New York, New York 10027, USA — 2Department of Chemistry, Columbia University, New York, New York 10027, USA
Advances in light sources and time resolved spectroscopy have made it possible to excite specific atomic vibrations in solids and to observe the resulting changes in electronic properties but the mechanism by which phonon excitation causes qualitative changes in electronic properties, is still under debate. Here, we show that the dominant symmetry-allowed coupling between electron density and dipole active modes implies an electron density-dependent squeezing of the phonon state which provides an attractive contribution to the electron-electron interaction, independent of the sign of the bare electron-phonon coupling and with a magnitude proportional to the degree of laser-induced phonon excitation. Reasonable excitation amplitudes lead to non-negligible attractive interactions that may cause significant transient changes in electronic properties including superconductivity. The mechanism is generically applicable to a wide range of systems, offering a promising route to manipulating and controlling electronic phase behavior in novel materials. Building on these results we analyze the non-equilbrium response of the electronic system and discuss implications for experimentally accessible observables, such as optical conductivity.