Seminare, Kolloquien & Sitzungen
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D-PHYS - Beginn Unterricht
- ETH Zürich, Hönggerberg - Tue 19.09.2017 8:00
D-PHYS - Beginn Herbstsemester 2017 / Start of Autumn Semester 2017
- ETH Zürich, Hönggerberg - Mon 18.09.2017 8:00
D-PHYS (members only) - PK retreat
- Schloss Au - Fri 15.09.2017 9:00-16:30
D-PHYS (members only) (ETH Zürich) - Visit VPFW Prof. D. Günther
- ETH Zürich, Hönggerberg HPF G 6 - Thu 14.09.2017 14:00-18:00
D-PHYS (members only) - Notenkonferenz
- ETH Zürich, Hönggerberg - Thu 14.09.2017 11:45
D-PHYS (members only) - Vollversammlung der D-PHYS Betriebe
- ETH Zürich, Hönggerberg HPV G 5 - Thu 14.09.2017 9:00-12:00
D-PHYS - Knabenschiessen / "Knabenschiessen" (local Zurich holiday)
- ETH Zürich, Hönggerberg - Mon 11.09.2017 12:00-18:00
D-PHYS - Ende Prüfungssession
- ETH Zürich, Hönggerberg - Fri 1.09.2017 18:00
D-PHYS - Beginn Prüfungssession
- ETH Zürich, Hönggerberg - Mon 7.08.2017 8:00
D-PHYS - Schweizer Nationalfeiertag / Swiss National Day
- ETH Zürich, Hönggerberg - Tue 1.08.2017 8:00-18:00
D-PHYS - Promotionsfeier / Doctorate awards ceremony
- ETH Zürich, Hönggerberg HPH G 1 - Fri 21.07.2017 17:00
Davide Bossini (University of Tokyo, Japan) - Femtosecond quantum spin dynamics at the edges of the Brillouin zone in antiferromagnets
The investigation of the interaction between femtosecond laser pulses and magnetic materials has already revealed the tremendous potential of this approach for the ultrafast manipulation of spins[1,2]. In particular, the all - optical control of the magnetic order in antiferromagnets has become relevant, given the recent surge of interest in this class of materials for spintronics purposes. The peculiarity of l aser pulses, when compared to other stimuli, consists in the possibility to excite, manipulate and detect spin excitations on the femtosecond timescale which meets the requirement for ever - faster approaches to the control of magnets. However, the collectiv e spin excitations photoinduced hitherto in antiferromagnets are limited to low - wavevector magnons, which are the lowest - frequency modes in the dispersion of a typical antiferromagnet[1,3 - 5]. Recently the highest - frequency modes, which are magnons with wav evector near the edges of the Brillouin zone, have been impulsively photo - excited via a coherent light - scattering approach. Remarkably, a complete manipulation of the phase and amplitude of coherent magnons with frequency equal to 22 THz and 1 nm wavele ngth (i.e. femto - nanomagnons ) was achieved. Even more excitingly, further investigation of the femto - nanomagnonics regime demonstrated that it has little in common with the conventional spin dynamics triggered by nearly - zero - wavevector magnons . The classical thermodynamic concepts commonly employed in the description of magnetic dynamics critically do not hold in this newly discovered regime. This observation called for the development of a novel theoretical quantum - mechanical framework, based on magnonic coherent states. A proper equation of motion was derived within our model; in addition some intruiging predictions of our formalism suggest that the photo - generated magnons are intrinsically entangled.
- ETH Zürich, Hönggerberg HPF G 6 - Wed 12.07.2017 16:45-18:00
Shohei Hayashida (University of Tokyo, Tokyo, Japan) - Magnetic state of classical kagome lattice antiferromagnet NaBa2Mn3F11 investigated by neutron scattering
In a classical Kagome lattice antiferromagnet, ground state is infinitely degenerated. The degeneracy is lifted up by various perturbations. NaBa2Mn3F11 is a model compound of the classical Kagome lattice antiferromanget . We performed powder neutron diffraction experiments to identify the ground state. Magnetic Bragg peaks are clearly observed below T = 2 K, meaning that the ground state is a magnetically ordered state. Combination of representation analysis and Rietveld refinement reveals that the magnetic structure exhibits the 120º structure with a magnetic propagation vector k = (0, 0, 0). Classical calculation of the ground state suggests that the non-negligible magnetic dipolar interaction is responsible for the determined 120º structure in NaBa2Mn3F11. In the seminar, I will talk about the magnetic state of NaBa2Mn3F11 through the results of the neutron scattering experiment.  H. Ishikawa et al., J. Phys. Soc. Jpn. 83, 043703 (2014).
- ETH Zürich, Hönggerberg HPF G 6 - Thu 6.07.2017 16:45-18:00
Sourin Das (Indian Institute of Science Education and Research Kolkata, India) - Non-local multi-particle geometric phases in electronic intensity interferometry
Abs: Berry's discovery of the geometric phase in 1984 led to a deeper understanding of wide range of phenomena in different areas of physics starting from molecular physics to condensed matter systems. In this talk, I will first provide an introduction to the concept of geometric phase in spirit of Berry's definition and then relate it to its generalized version as anticipated in earlier works of Pancharatnam. I shall then apply Pancharatnam's ideas to obtain non-local and multi-particle geometric phase in the context of electronic version of the Hanbury-Brown and Twiss intensity interferometer. I will discuss a possible experimental realization of this effect by exploiting edge states of two-dimensional topological insulators (2d TI edge states). It will be shown that the electrical transport in quantum spin Hall (an example of the 2d TI state) edge can host a two particle Aharonov - Bohm (AB) effect in spin space which essentially is an example of multi-particle and non-local geometric phase. This two particle “spin A-B effect” stems from an effective AB flux piercing a two particle loop identified on the Bloch sphere which can be attributed to an abstract monopole of strength 1/2 placed at the origin of the sphere.
- ETH Zürich, Hönggerberg HIT E 41.1 - Tue 4.07.2017 10:00
Richard Hlubina (Comenius University in Bratislava, Slovakia) - Pair-breaking vs. pair-conserving scattering in superconductors: implications for ARPES and superfluid stiffness
The recent experimental study of how the superfluid stiffness in the cuprates disappears with overdoping  calls for a more complete understanding of the effect of disorder in unconventional d-wave superconductors. Of crucial importance is to distinguish pair-breaking (large-angle) from pair-conserving (small-angle) scattering processes, since they affect electromagnetic properties in very different ways . I will argue that there exists a simple generic formula for the electron Green's function which takes into account both types of processes, and which moreover has the correct analytic properties, satisfies the known sum rules, and its spectral function is positive-definite [3,4]. I will demonstrate that the recent high-resolution ARPES data  can be fitted well by this formula, and that from the fit one can directly determine the relative weight of the pair-breaking and pair-conserving scattering processes. We find that in the cuprates the small-angle scattering processes are dominant , in agreement with arguments based on comparison between ARPES and transport. I will also present the implications of our theory for the doping- and temperature-dependence of the superfluid stiffness in overdoped cuprates.  I. Bozovic et al, Nature 536, 309 (2016).  F. Herman and R. Hlubina, preprint arXiv:1705.04674.  F. Herman and R. Hlubina, Phys. Rev. B 95, 094514 (2017).  F. Herman and R. Hlubina, Phys. Rev. B 94, 144508 (2016).  T. Kondo et al., Nat. Commun. 6, 7699 (2015).
- ETH Zürich, Hönggerberg HIT E 41.1 - Tue 27.06.2017 11:00