Ultrafast Quantum Physics in Amplitude and Phase - UltraPhase, ERC Advanced Grant
Ultrafast phenomena related to and/or accessible only via the absolute temporal phase of electronic, vibrational and spin coherent excitations in condensed matter are studied via electromagnetic transients in the multi-terahertz regime. The project also includes innovative aspects of quantum optics, femtosecond lasers and terahertz technology. Four central objectives are as follows:
(i) Establishing rapid quantum oscillatory motion as the earliest regime in the dynamics and transport of electrons in solids. Fundamental phenomena like the temporal buildup of effective mass in semiconductors and Zitterbewegung in graphene are accessed directly.
(ii) Studying nonclassical light emission predicted to emerge after non-adiabatic perturbation of ultrastrongly coupled systems of light and matter. The quantum properties of radiation released by such processes are investigated at the uncertainty limit between amplitude and phase of the light field.
(iii) Observation and control of charge and spin electronic properties of solids under extremely high transient electric or magnetic bias provided by a novel source of phase-locked multi-terahertz pulses allowing analysis with a resolution significantly below half a cycle of light.
(iv) Field-resolved photon-echo studies in the mid infrared. Unprecedented insights into complex phenomena like the interplay between low-energy degrees of freedom in high-temperature superconductors and intermolecular motion in liquids are envisioned.
New developments in ultrabroadband terahertz technology will enable the experiments:
(a) Generation of phase-locked electromagnetic transients with precisely controlled shape of the electric field like quasi-monopolar terahertz shock waves or single-cycle pulses with field amplitudes up to 30 MV/cm.
(b) Coherent detection of electric fields with bandwidth up to 200 THz and sensitivity at the uncertainty limit, giving access to the quantum properties of electromagnetic waves in amplitude and phase.
- FB Physik
|(2018): Signatures of transient Wannier-Stark localization in bulk gallium arsenide Nature Communications ; 9 (2018), 1. - 2890. - eISSN 2041-1723|
Many properties of solids result from the fact that in a periodic crystal structure, electronic wave functions are delocalized over many lattice sites. Electrons should become increasingly localized when a strong electric field is applied. So far, this Wannier-Stark regime has been reached only in artificial superlattices. Here we show that extremely transient bias over the few-femtosecond period of phase-stable mid-infrared pulses may localize electrons even in a bulk semiconductor like GaAs. The complicated band structure of a three-dimensional crystal leads to a strong blurring of field-dependent steps in the Wannier-Stark ladder. Only the central step emerges strongly in interband electro-absorption because its energetic position is dictated by the electronic structure at an atomic level and therefore insensitive to the external bias. In this way, we demonstrate an extreme state of matter with potential applications due to e.g., its giant optical non-linearity or extremely high chemical reactivity.
|(2016): Photon-assisted electronic and spin transport in a junction containing precessing molecular spin Physical Review B ; 93 (2016), 7. - 075402. - ISSN 2469-9950. - eISSN 2469-9969|
We study the ac charge and -spin transport through an orbital of a magnetic molecule with spin precessing in a constant magnetic field. We assume that the source and drain contacts have time-dependent chemical potentials. We employ the Keldysh nonequilibrium Green’s functions method to calculate the spin and charge currents to linear order in the time-dependent potentials. The molecular and electronic spins are coupled via exchange interaction. The time-dependent molecular spin drives inelastic transitions between the molecular quasienergy levels, resulting in a rich structure in the transport characteristics. The time-dependent voltages allow us to reveal the internal precession time scale (the Larmor frequency) by a dc conductance measurement if the ac frequency matches the Larmor frequency. In the low-ac-frequency limit the junction resembles a classical electric circuit. Furthermore, we show that the setup can be used to generate dc-spin currents, which are controlled by the molecular magnetization direction and the relative phases between the Larmor precession and the ac voltage.
|(2014): Sub-cycle slicing of phase-locked and intense mid-infrared transients New Journal of Physics ; 16 (2014), 6. - S. 063033. - ISSN 1367-2630. - eISSN 1367-2630|
We demonstrate sub-cycle manipulation of mid-infrared optical waveforms in the time domain. This goal is accomplished via efficient reflection at a semiconductor surface induced by femtosecond interband excitation. The ultrafast response of this process allows slicing of high-field multi-terahertz transients down to the single optical cycle. Ultrabroadband and phase-stable transients with peak amplitudes beyond 10 MVcm-1 are obtained, paving the way for efficient coherent control of light–matter interaction in the non-perturbative regime. The microscopic analysis of electron–hole plasma generation in germanium reveals a decisive role of two-photon absorption allowing efficient slicing up to midinfrared frequencies.
|Sonstige EU||839/11||no information|
|Period:||01.01.2012 – 31.12.2016|