Programm für das Sommersemester 2025
Thursdays, 14:00 Uhr s.t.
JGU
01 122 Newton-Raum
| 07.04.25 | Prof. Junichiro Kono, Rice University Houston United States | |
Recent advances in optical studies of condensed matter have led to the emergence of a variety of phenomena that have conventionally been studied in quantum optics. These studies have not only deepened our understanding of light-matter interactions but also introduced aspects of many-body effects inherent in condensed matter. This talk will describe our recent studies of Dicke cooperativity, i.e., many-body enhancement of light-matter interaction, a concept in quantum optics, in condensed matter. This enhancement has led to the realization of the ultrastrong coupling (USC) regime, where new phenomena emerge through the breakdown of the rotating wave approximation (RWA). We will first describe our observation of USC in a 2D electron gas in a high-Q terahertz cavity in a magnetic field, and definitive evidence for the vacuum Bloch-Siegert shift, a signature of the breakdown of the RWA. Further, we have shown that cooperative USC also occurs in magnetic solids in the form of matter-matter interaction, i.e., spin-magnon and magnon-magnon interactions in rare earth orthoferrites. Particularly, the exchange interaction of N paramagnetic Er3+ spins with an Fe3+ magnon field in ErFeO3 has exhibited a vacuum Rabi splitting whose magnitude is proportional to N1/2 [6]. In the lowest temperature range, these cooperative interactions lead to a magnonic superradiant phase transition. These results provide a route for understanding, controlling, and predict novel phases of condensed matter. | ||
| 14:00 Uhr s.t., 05-427 Sozialraum der Thep | ||
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| 07.04.25 | Prof. Junichiro Kono, Rice University Houston United States | |
Recent advances in optical studies of condensed matter have led to the emergence of a variety of phenomena that have conventionally been studied in quantum optics. These studies have not only deepened our understanding of light-matter interactions but also introduced aspects of many-body effects inherent in condensed matter. This talk will describe our recent studies of Dicke cooperativity, i.e., many-body enhancement of light-matter interaction, a concept in quantum optics, in condensed matter. This enhancement has led to the realization of the ultrastrong coupling (USC) regime, where new phenomena emerge through the breakdown of the rotating wave approximation (RWA). We will first describe our observation of USC in a 2D electron gas in a high-Q terahertz cavity in a magnetic field, and definitive evidence for the vacuum Bloch-Siegert shift, a signature of the breakdown of the RWA. Further, we have shown that cooperative USC also occurs in magnetic solids in the form of matter-matter interaction, i.e., spin-magnon and magnon-magnon interactions in rare earth orthoferrites. Particularly, the exchange interaction of N paramagnetic Er3+ spins with an Fe3+ magnon field in ErFeO3 has exhibited a vacuum Rabi splitting whose magnitude is proportional to N1/2 [6]. In the lowest temperature range, these cooperative interactions lead to a magnonic superradiant phase transition. These results provide a route for understanding, controlling, and predict novel phases of condensed matter. | ||
| 14:00 Uhr s.t., 05-427 Sozialraum der Thep | ||
Sonderseminar | ||
Special Event |
zukünftige Termine
| 22.05.25 | Rembert Duine, Eindhoven University of Technology | |
Synthetic antiferromagnets are magnetic multilayers consisting of two or more ferromagnetic layers that are coupled antiferromagnetically. They play an important role in spintronic devices, e.g., as field sensors, and as synthetic materials for fundamental explorations. In this talk, I will highlight the use of synthetic antiferromagnets for quantum information science with spin waves, i.e., for quantum magnonics. Examples that are discussed are unidirectionally-coupled magnetic layers that give rise to magnon quantum amplification, and new ways to entangle magnons between two ferromagnetic layers. Both these examples rely on the possibility to engineer both the interactions between the layers, and the interactions of the magnetic layers with the environment. This tunability highlights the potential of synthetic antiferromagnets for quantum magnonics. | ||
| 14:00 Uhr s.t., 01 122 Newton-Raum | ||
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| 12.06.25 | Prof. Dr. Yaroslav Tserkovnyak, UCLA | |
In this talk, I will review two device concepts based on nonlinear dissipative magnetic dynamics. First, we revisit the problem of spin superfluidity, which has been predicted to facilitate coherent spin transport. We propose to both exhibit and exploit this elusive transport phenomenon via the "spin-superfluid quantum interference device" (spin SQUID) — inspired by its superconducting (rf SQUID) and superfluid helium (SHeQUID) counterparts. In particular, we discuss its potential electric-field sensing functionality based on the microwave response of the simplest pertinent structure: a magnetic ring with a single weak link. In the second part of the talk, we systematically address the pseudo-Hermitian physics of dynamically-coupled magnetic macrospins, with a focus on non-Hermitian mode hybridization and its potential utility as a scalable building block for dynamic Ising machines. | ||
| 14:00 Uhr s.t., 01 122 Newton-Raum | ||
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| Koordination: | |
Univ-Prof. Dr. Jure Demsar |