Archive 2019

Room: Seminar Room IV, O1.111 Host: Andrea Cavalleri

Electronic dynamics of strange metals

MPSD Seminar
The normal state of unconventional superconductors often exhibits anomalous transport properties and it is commonly referred to as a “bad” or “strange” metal. Understanding its collective charge dynamics, which defies the standard quasiparticle description of a Fermi liquid, is an outstanding challenge of modern condensed matter physics.In this talk, I will present a direct measurement of the collective charge dynamics of the strange metal using inelastic electron scattering. First, I will discuss how normal-state Bi2Sr2CaCu2O8+d is defined by a featureless, localized continuum, undergoing a low-temperature massive spectral weight redistribution. I will then describe how such a phase is found to coexist with a low-energy Fermi liquid in Sr2RuO4.These results indicate that strange metals are highly localized in space and dissipate on ultrafast timescales, seemingly bound only by quantum limits. Implications for the occurrence of high-temperature superconductivity will be discussed. [more]

Ultrafast single-molecule videography and choreography

MPSD Seminar
To understand the function of condensed matter, it would be desirable to directly watch its atomistic building blocks dynamically interact on their intrinsic length and time scales. Recently, lightwave electronics has made this long-standing dream come true. The idea is to exploit the carrier wave of light as an ultrafast, contact-free bias to interrogate and control the nanocosm. I will first review how lightwaves can drive electrons in solids into surprising sub-cycle quantum motion. By combining this idea with the sub-angstrom spatial resolution of scanning tunnelling microscopy we can set an ultrashort time window for single-electron tunnelling into a single orbital and record first atom-scale slow-motion movies of individual vibrating molecules. Finally, I will show how to directly exert femtosecond atomic forces, which can selectively choreograph a coherent structural motion of a single-molecule switch in its electronic ground state. This stunningly direct access to the atomistic world may tailor key elementary dynamics in nature and steer (bio)chemical reactions or ultrafast phase transitions, on their intrinsic spatio-temporal scales. [more]
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