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DTSTART;TZID=Europe/Berlin:20250211T160000
DTEND;TZID=Europe/Berlin:20250211T170000
DTSTAMP:20260426T153320
CREATED:20250205T131157Z
LAST-MODIFIED:20250205T131249Z
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SUMMARY:TRR 360 Seminar: Cavity electrodynamics of correlated materials in Fabry-Pèrot optical  resonators Giacomo Jarc
DESCRIPTION:Cavity electrodynamics of correlated materials in Fabry-Pèrot optical resonators \nDr. Giacomo Jarc \nFriedrich-Alexander-Universität\, Erlangen-Nürnberg \n  \nThe possibility of engineering collective properties of bulk materials through cavity electrodynamics has been so far mostly explored in theoretical works and theory-based experimental proposals [1]. Only recently\, the development of new experimental platforms [2\, 3] has started to unlock the full potential of cavity-control of solid-state quantum materials and shed light on new pathways for light-matter coupling in a cavity-confined environment. \nIn this seminar\, I will discuss our recent study on the cavity-mediated thermal control of the metal-to-insulator transition in the charge-density-wave (CDW) material 1T-TaS2 [4]\, which show the possibility of reversible cavity-manipulation of a phase transition in a correlated material. We embed 1T-TaS2 into cryogenic tunable terahertz cavities [3] and show that a switch between conductive and insulating behaviours\, triggered by a large change in the sample temperature\, is obtained by mechanically tuning the distance between the cavity mirrors and their alignment. The large thermal modification observed is indicative of a Purcell-like scenario in which the spectral profile of the cavity modifies the energy exchange between the material and the external electromagnetic field [5]. \nWhen the cavity is tuned resonantly to the multiple IR-active vibrations of the CDW dielectric phase of 1T-TaS2\, we reveal the THz signatures of a multimode vibro-polariton mixing\, originating from the collective strong coupling of the CDW vibrations with the cavity field [6]. The estimated components of the polaritonic wave-functions show that the observed multimode polaritons have character from all the vibrational resonances as a consequence of the cavity-mediated hybridization. The Rabi splittings between the hybridized phonons are suppressed across the insulator-to-metal transition as a consequence of the screening of the free charges. Intriguingly\, we reveal that in proximity of the phase transition\, the phonon dissipations trigger the onset of a weak vibrational coupling regime in the cavity-confined material. \nWhen instead the cavity frequency is tuned within the spectral range of the continuum Drude excitation of 1T-TaS2\, we reveal that the quality factor of the cavity\, which quantifies the dissipative response of the coupled system\, is sensitive to the material phase. We measure indeed the lifetime of the cavity photons to decrease passing from the insulating to the metallic state. This evidence points to a scenario in which the free charges responsible for the Drude excitation can effectively couple to the cavity field and subsequently modulate the light-matter coupling within the Fabry-Pèrot resonator. \nOur findings show how cavity electrodynamics can play a role in the intricate equilibrium physics of complex materials\, possibly providing a new tool to control and engineer their cooperative properties. \n  \n[1] F. Schlawin\, D. M. Kennes\, and M. A. Sentef.\, “Cavity quantum materials”\, Applied Physics Reviews 9\, 011312 (2022). \n[2] G. Jarc\, S. Y. Mathengattil\, F. Giusti\, M. Barnaba\, A. Singh\, A. Montanaro\, F. Glerean\, E. M. Rigoni\, S. Dal Zilio\, S. Winnerl\, and D. Fausti\, “Tunable cryogenic terahertz cavity for strong light-matter coupling in complex materials”\, Rev. Sci. Instrum. 93\, 033102 (2022). \n[3] F. Appugliese\, J. Enkner\, G. Parravicini-Bagliani\, M. Beck\, C. Reichl\, W. Wegscheider\, G. Scalari\, C. Ciuti\, and J. Faist\, “Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect”\, Science 375\, 6584\, 1030-1034 (2022). \n[4] G. Jarc\, S. Y. Mathengattil\, A. Montanaro\, F. Giusti\, E. M. Rigoni\, R. Sergo\, F. Fassioli\, S. Winnerl\, S. Dal Zilio\, D. Mihailovic\, P. Prelovsek\, M. Eckstein\, and D. Fausti\, “Cavity-mediated thermal control of metal-to-insulator transition in 1T-TaS2”\, Nature 622\, 487-492 (2023). \n[5] F. Fassioli\, J. Faist\, M. Eckstein\, and D. Fausti\, “Controlling radiative heat through cavity electrodynamics”\, arXiv:2403.00851v1 [physics.optics] (2024). \n[6] G. Jarc\, A. Montanaro\, S. Y. Mathengattil\, E. M. Rigoni\, S. Dal Zilio\, and D. Fausti\, “Multimode vibrational coupling across the insulator-to-metal transition in 1T-TaS2 in THz cavities”\, J. Chem. Phys. 161\, 154711 (2024). \n\n\n\n\n\n\nVenue
URL:https://www.trr360.de/event/trr-360-seminar-cavity-electrodynamics-of-correlated-materials-in-fabry-perot-optical-resonators-giacomo-jarc/
LOCATION:University of Augsburg\, Room S-288 + Zoom
CATEGORIES:Seminar
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BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20250213T140000
DTEND;TZID=Europe/Berlin:20250213T150000
DTSTAMP:20260426T153320
CREATED:20250205T132127Z
LAST-MODIFIED:20250205T132316Z
UID:4632-1739455200-1739458800@www.trr360.de
SUMMARY:TRR 360 Seminar: Energy relaxation and dynamics in strongly correlated materials N. Peter Armitage
DESCRIPTION:Energy relaxation and dynamics in strongly correlated materials \nProf. Dr. N. Peter Armitage \nJohns Hopkins University\, Baltimore\, USA \n  \nIf a physical system is perturbed from equilibrium\, the rate that it equilibrates is an important measure of its physics. In condensed matter systems\, we are used to measuring such rates in the context of linear response to electromagnetic fields. For instance\, the rate that current decays in a metal after an electric field impulse can be related to the width of its low-frequency “Drude” response in the optical conductivity. The rate that polarization decays after polling a liquid with an E field corresponds to the width of the broad peak in the Debye relaxational functional form. In contrast\, the rate of energy relaxation is a fundamental rate that governs many processes in solids\, but which is unfortunately not measured straightforwardly via conventional electrodynamic linear response. However quite generically\, this rate can be measured in non-linear chi3 spectroscopies. I will discuss recent technical developments in the form of THz range 2D coherent spectroscopy (and its relatives) that allow us to get new information about energy relaxation in correlated and topological metals\, as well as disordered electron glasses. I will discuss a number of systems and phenomena in which unconventional dynamics and energy relaxation govern their low energy behavior. I will give number of examples of the power of these new techniques to strongly interacting metals\, Dirac semimetals\, collective modes in superconductors\, electron glasses\, and 1D spin chains. \n  \n[1] Fahad Mahmood et al.\, “Observation of a marginal Fermi glass”\, Nature Physics (2021). \n[2] D. Barbalas et al.\, “Energy Relaxation and Dynamics in the Correlated Metal Sr2⁢RuO4 via Terahertz Two-Dimensional Coherent Spectroscopy”\, Phys. Rev. Lett. 134\, 036501 (2025). \n[3] K. Katsumi et al.\, “Revealing novel aspects of light-matter coupling in terahertz two-dimensional coherent spectroscopy: the case of the amplitude mode in superconductors”\, Phys. Rev. Lett. 132\, 256903 (2024). \n[4] R. Bhandia et al.\, “”Anomalous electronic energy relaxation and soft phonons in the Dirac semimetal Cd3As2“\, Phys. Rev. B 110\, 075131 (2024). \n[5] R. Bhandia et al. “Energy and momentum relaxation through the Curie temperature in an itinerant ferromagnet”\, https://arxiv.org/abs/2412.08749. \n\n\n\n\n\n\nVenue
URL:https://www.trr360.de/event/trr-360-seminar-energy-relaxation-and-dynamics-in-strongly-correlated-materials-n-peter-armitage/
LOCATION:University of Augsburg\, Room S-288 + Zoom
CATEGORIES:Seminar
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BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20250225T140000
DTEND;TZID=Europe/Berlin:20250225T150000
DTSTAMP:20260426T153320
CREATED:20250217T164504Z
LAST-MODIFIED:20250221T151234Z
UID:4657-1740492000-1740495600@www.trr360.de
SUMMARY:TRR 360 Seminar: Optically induced quantum spin-disordered state in the Kitaev material α-RuCl3 Paul H. M. van Loosdrecht
DESCRIPTION:Optically induced quantum spin-disordered state in the Kitaev material α-RuCl3 \nProf. Dr. Paul H. M. van Loosdrecht \nUniversität zu Köln \nOne way to characterize quantum spin-liquids is through the fractionalization of spin excitations. A prime example of this is found in the exactly solvable Kitaev model of spin-1/2 moments with anisotropic exchange interactions on a tri-coordinated lattice. To find examples of this kind of physics in nature turns out to be challenging. The currently best-known examples of materials in which Kitaev-like physics plays a central role are the layered spin-orbit entangled J=1/2 systems Na2IrO3\, α-Li2IrO3\, and α-RuCl3. However\, these materials all possess additional interactions\, which\, among other\, lead to a magnetically ordered state at low temperature preventing the formation of a pure Kitaev spin-liquid (KSL) state. Apart from the ongoing quest for materials showing a true KSL ground state\, one can also destabilize the magnetic order in the existing materials\, which potentially can induce the sought-after KSL state. In this contribution I will discuss two methods to destabilize magnetic order in α-RuCl3. The first one is through the application of an in-plane magnetic field. Though it has been shown by various authors that this indeed leads to suppression of the ordered state in α-RuCl3\, the nature of the field-induced state is still not fully clear. The second approach is a pump-probe method which creates holon and doublon excitations. These excitations are found to couple efficiently to magnetic excitations which in turn disorder the magnetically ordered state. For sufficiently high excitation densities the magnetic order is fully suppressed\, leading to a quantum disordered magnetic state. \n\n\n\n\n\n\nVenue
URL:https://www.trr360.de/event/trr-360-seminar-optically-induced-quantum-spin-disordered-state-in-the-kitaev-material-%ce%b1-rucl3-paul-h-m-van-loosdrecht/
LOCATION:University of Augsburg\, Room S-288 + Zoom
CATEGORIES:Seminar
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