Seminars, Colloquia & Meetings

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Please note: The entries in this list appear currently in reverse chronological order.

Sep 19, 2017

D-PHYS - Beginn Unterricht


- ETH Zürich, Hönggerberg - Tue 19.09.2017 8:00

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Sep 18, 2017

D-PHYS - Beginn Herbstsemester 2017 / Start of Autumn Semester 2017


- ETH Zürich, Hönggerberg - Mon 18.09.2017 8:00

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Sep 15, 2017

D-PHYS (members only) - PK retreat


- Schloss Au - Fri 15.09.2017 9:00-16:30

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Sep 14, 2017

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

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Sep 14, 2017

D-PHYS (members only) - Notenkonferenz


- ETH Zürich, Hönggerberg - Thu 14.09.2017 11:45

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Sep 14, 2017

D-PHYS (members only) - Vollversammlung der D-PHYS Betriebe


- ETH Zürich, Hönggerberg HPV G 5 - Thu 14.09.2017 9:00-12:00

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Sep 11, 2017

D-PHYS - Knabenschiessen / "Knabenschiessen" (local Zurich holiday)


- ETH Zürich, Hönggerberg - Mon 11.09.2017 12:00-18:00

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Sep 1, 2017

D-PHYS - Ende Prüfungssession


- ETH Zürich, Hönggerberg - Fri 1.09.2017 18:00

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Aug 7, 2017

D-PHYS - Beginn Prüfungssession


- ETH Zürich, Hönggerberg - Mon 7.08.2017 8:00

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Aug 1, 2017

D-PHYS - Schweizer Nationalfeiertag / Swiss National Day


- ETH Zürich, Hönggerberg - Tue 1.08.2017 8:00-18:00

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Jul 21, 2017

D-PHYS - Promotionsfeier / Doctorate awards ceremony


- ETH Zürich, Hönggerberg HPH G 1 - Fri 21.07.2017 17:00

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Jul 12, 2017

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[6]. 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[6]. 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[7].
- ETH Zürich, Hönggerberg HPF G 6 - Wed 12.07.2017 16:45-18:00

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Jul 6, 2017

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 [1]. 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. [1] 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

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Jul 4, 2017

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

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Jun 23, 2017

Bernd Krauskopf (University of Auckland, New Zealand) - Pulsing lasers with delayed optical feedback

Abstract: Semiconductor lasers with saturable absorber (SLSA) may produce trains of short pulses. In applications, such as clock generation and optical telecommunication, these need to be very regularly, and delayed optical feedback has been suggested as a control strategy to achi e ve this. From a mathematical perspective, such a system is described by delay differential equations. This class of sys tems features an infinite dimensional phase space, yet is still amenable to bifurcation analysis with advanced numerical tools. This allows one to map out regions in parameter space where different behavior can be found. As an example of the scope of this approach, we consider the Yamada model with delay, which is a system of three differential equations for the gain, the absorber and the intensity with incoherent delayed optical feedback. Our bifurcation analysis reveals an increasing complexity of feedbac k - induced dynamics, including multi - frequency oscillations and a large degree of multistability. Its predictive power for an experiment with a micropillar SLSA will be discussed.
- ETH Zürich, Hönggerberg HPF G 6 - Fri 23.06.2017 11:00-12:30

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Jun 23, 2017

Clemens Mueller (The University of Queensland, Australia) - On-chip microwave circulators - Breaking time-reversal symmetry with quantum phase slips

We present the design of a passive, on-chip microwave circulator based on superconducting quantum phase slip (QPS) junctions. QPS junctions are dual circuit-elements that are equivalent to Josephson junctions under the exchange of voltage and current [1] and they have recently been employed to observe coherent quantum phase slips [2] and as the basic buidling block of a new type of flux qubit [3]. In our proposed QPS-junction based circulator, the three ports of the circulator are inductively connected to superconducting loops hosting trapped flux quanta. The role of a symmetry-breaking magnetic field is played by an external gate charge on a central island. The design is similar to one previously proposed using Jopsephson junctions [4], but exchanges the charge and flux degrees of freedom. The QPS circulator therefore is much less sensitive to environmental perturbations, since fluctuations in background magnetic flux are many orders of magnitude suppressed as compared to charge fluctuations. We derive the properties of a QPS based circulator design from a Lagrangian description of the circuit and use the model to calculate the circulator efficiency of the system and study the effect of detrimental influences such as charge and magnetic flux noise and imperfections in device fabrication. We find that our design offers high isolation even when taking into account realistic fabrication imperfections and experimental conditions and find a circulator bandwidth in excess of 100 MHz for realistic device parameters. [1] Mooij and Nazarov, Nature Physics 2, 169–172 (2006). [2] Astafiev, Ioffe, Kafanov, Pashkin, Arutyunov, Shahar, Cohen, and Tsai, Nature 484, 355– 358 (2012). [3] Peltonen, Astafiev, Korneeva, Voronov, Korneev, Charaev, Semenov, Golt’sman, Ioffe, Klapwijk, and Tsai, Physical Review B 88, 220506 (2013). [4] Koch, Houck, Le Hur, and Girvin, Physical Review A 82, 043811 (2010)
- ETH Zürich, Hönggerberg HPF D 12 - Fri 23.06.2017 10:00

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Jun 22, 2017

various speakers - Contextuality workshop


- ETH Zürich, Zentrum HG D 1.2 - 22.06-23.06 2017 9:30-17:30

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