Miguel Bastarrachea-Magnani

Universidad Autónoma
Metropolitana-Iztapalapa

Quantum probing of classical structures in the Dicke Hamiltonian

When: 12:00-13:00 CET, November 21st (Thursday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

The Dicke Hamiltonian is a paradigmatic model of quantum
optics that describe the ultra-strong coupling between light and
collective modes of matter. This interaction results in the creation of
polaritons, hybrid quantum states that share properties of their
original components. Originally proposed to describe atoms in cavities,
the model has now become a general formulation of the spin-boson
interaction with applications in polariton physics and various systems
within the context of quantum information, atomic physics, and condensed
matter. In this talk, I will address the model’s theoretical richness
for exploring the quantum-classical correspondence. Thanks to its
collective nature, it is possible to easily identify a classical
counterpart and use quantum localization techniques to probe, identify,
and quantify structures in phase space, regularity, and chaos,
establishing a route to explore other, more complex, interacting quantum
systems.

Gerhard Klimeck

Purdue University, West Lafayette, IN 47907, USA

From Atomistic, Non-Equilibrium Quantum Statistical Mechanics Theory
to Today’s Transistor Design and Global Impact – A 25-Year Journey

When: 11:00-12:00 CET, September 18th (Wednesday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

30 years ago, the appropriate quantum transport theories, basis sets, algorithms, user interfaces, and dissemination methods for quantum device modeling were subjects of intense debate and uncertainty. The development of the Nanoelectronic MOdeling (NEMO) toolset commenced in 1994 at Texas Instruments, continued in 1998 and NASA/JPL, and has been ongoing at Purdue since 2004. Modern nanoscale transistor design extensively employs advanced quantum transport modeling tools, representing physical devices in three dimensions with atomistic basis sets. The NEMO implementations of the Non-Equilibrium Green Function (NEGF) formalism with atomistic tight-binding basis have become the benchmark for quantitative and predictive device simulation. This methodology has now been widely adopted by most device modeling research teams. In 2015, Intel integrated NEMO5 into their in-house design suite, utilizing a top-100 ranked supercomputer for design explorations [1]. Silvaco initiated commercialization efforts [2] in 2018, with industry leaders such as Samsung and TSMC developing their in-house solutions based on NEMO. NEMO’s capability to accurately model crystal orientations and strain in complex systems facilitated the development of Texas Instruments’ rotated substrate technology in 2004 [3], significantly impacting chips used in billions of cell phones. Contemporary 3D FinFETs [4] and nanosheet transistors share the 5 nm central length characteristics with 1D resonant tunneling diodes (RTDs). The quantitative and predictive modeling of 1D RTDs (1994-1997) established the standards necessary for today’s 3D nano-transistors.

NEMO’s applications extend beyond usage by experts equipped with specialized computational hardware. Over 25,000 users on nanoHUB.org, the pioneering comprehensive scientific computing cloud platform, have investigated various nanoscale devices such as nanowires, ultra-thin-body transistors, and quantum dots utilizing the intuitive NEMO/OMEN tools. These tools are supplemented by straightforward applications, rendering them accessible to a broad spectrum of users. Notably, more than fifty percent of nanoHUB’s simulation users participate in formal educational settings across 1,000 institutions globally, immersing themselves in device exploration and modeling principles. nanoHUB hosts 700+ apps and tools, along with over 170 courses.

This presentation will provide an overview of the critical physical phenomena needed to be captured for realistic device design, how high-performance-computing can deliver results to engineers & students, and how NEMO has been deployed on nanoHUB.org.

This work would not have been possible without my hundreds of collaborators who helped to build, test drive, break, and rebuild NEMO/OMEN [5-9,12-14] and nanoHUB [10,11].  I have the deepest appreciation for their hard work, dedication and in most cases their personal friendship. The citations here just cover some of the fundamental developments. Citations to these papers lead to hundreds of publications enabled by my collaborators and friends.

[1] Mark Stettler et al., IEDM, 39.1.1 (2019)
[2] Silvaco – Victory Atomistic, silvaco.com
[3] RC Bowen et al., US patent 7,268,399 (2004)
[4] G. Yeap et al., IEDM, 36.7.1 (2019)
[5] G. Klimeck, et al., APL Lett. 67, 2539 (1995)
[6] RC Bowen, et al., JAP 81, 3207 (1997)
[7] Jing Wang, et al., APL. 86, 093113 (2005)
[8] M Luisier, et al., Phys. Rev. B 74, 205323 (2006)
[9] G Klimeck el al, Superlatt. and Microstr., 27, 77, (2000)
[10] G Klimeck, et al, IEEE CISE, Vol. 10, 17 (2008)
[11] M. Hunt et al, PLoS ONE 17(3): e0264492.
[12] R Lake, et al.,JAP 81, 7845 (1997)
[13] G. Klimeck, et al, Computer Modeling in Engineering and Science (CMES) 3, 601-642 (2002).
[14] S Steiger et al., IEEE Tr. Nanotechn., 10, 1464, (2011)

Elton J. G. Santos

Higgs Centre for Theoretical Physics, Institute for Condensed Matter and Complex Systems – School of Physics and Astronomy, The University of Edinburgh, UK

 Exploring the Limits of Ultrafast Magnetism in Quantum Materials 

When: 12:00-13:00 CET, June 5th (Wednesday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

 Long searched but only now discovered two-dimensional (2D) magnets are one of the selected group of materials that retain or impart strongly spin correlated properties at the limit of atomic layer thickness. In this presentation, I will discuss how different layered compounds (e.g., CrX3 (X=F, Cl, Br, I), MnPS3, Fe5-xGeTe2, Cr2Ge2Te6) can provide new playgrounds for applications and fundamental exploration of spin correlations involving quantum-effects, topological spin-excitations and ultrafast laser pulses. In particular, I will show how van der Waals magnets do not require any magnetic anisotropy to stabilize 2D magnetism and demonstrate the null valid of the Mermin-Wagner theorem in practical applications. Moreover, some recent results of ultrafast laser excitations on different vdW heterostructures will be shown towards all-optical control of their magnetic properties with efficient heat management. 

Johannes Feist

Department of Theoretical Condensed Matter Physics, Universidad Autonoma de Madrid, Spain

Using cavities to modify material properties

When: 12:00-13:00 CET, May 23th (Thursday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

The use of cavity quantum electrodynamical effects, i.e., of vacuum electromagnetic fields, to modify material properties has rapidly gained popularity and interest in the last decade. A canonical example of this is strong light-matter coupling, reached when the interaction of material excitations with confined light modes overcomes dissipation effects and the two parts hybridize to form mixed light-matter eigenstates, so-called polaritons. These polaritons inherit properties of both light and matter excitations and additionally display fundamentally new phenomena. The large range of possible material systems and cavity architectures opens a rich playground for novel functionalities. In the talk, I will discuss several topics related to this overall field, including the modification and photophysics and photochemistry in organic molecules, some fundamental results and pitfalls for the modification of low-energy excitations, and recent progress on few-mode field quantization in complex nanophotonic structures, i.e., strategies to obtain the construction of cavity-QED-like models for arbitrary cavity geometries and materials.

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Ricardo Lobo

ESPCI Paris – PSL University – CNRS – Sorbonne Université, France

Correlations and dispersive Dirac physics in the quantum material family BaCoS2-BaNiS2 – Reverse band-structure engineering of the optical conductivity

When: 12:00-13:00 CET, May 30th (Thursday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

BaCoS2 and BaNiS2 are the end members of a solid solution that shows a vast array of quantum properties. The Co material is close to a strongly correlated insulator with an antiferromagnetic transition, as well as a structural phase transition, around room temperature. At 28% Ni doping this material undergoes an electronic metal-insulator phase transition to a Drude metal. The metallic state persists all the way to the pure Ni compound. At this point, in addition to a Drude peak, we observe a strong contribution from bands with linear dispersion at the Fermi level, which give origin to dispersive Dirac nodal lines. We measured the optical conductivity of these materials and combined them with ab-initio calculations to reverse engineer the role of each band in the physical response of these materials. We explained uncommon features in their optical response such as a linear dispersion of the optical conductivity [1] and the existence of an isosbestic line separating a spectral-weight transfer across Dirac nodal states [2].

[1] D. Santos-Cottin, Y. Klein, P. Werner, T. Miyake, L. de’Medici, A. Gauzzi, R.P.S.M. Lobo, and M. Casula, Linear behavior of the optical conductivity and incoherent charge transport in BaCoS2, Phys. Rev. Materials 2, 105001 (2018). arXiv: 1712.01539.

[2] D. Santos-Cottin, M. Casula, L. de’Medici, F. Le Mardelé, J. Wyzula, M. Orlita, Y. Klein, A. Gauzzi, A. Akrap, and R.P.S.M. Lobo, Optical conductivity signatures of open Dirac nodal lines, Phys. Rev. B 104, L201115 (2021). arXiv: 2104.05521.

Nicolas Leconte

University of Seoul, Korea

Christopher W. Wächtler 

Department of Physics

University of California at Berkeley

Dissipation as versatile resource for collective quantum dynamics

When: 12:00-13:00 CET, April 16th (Tuesday), 2024

Where: Salon de Actos, ICMM-CSIC, Campus de Cantoblanco, Madrid

The widespread belief is that quantum systems need to be protected from the environment as well as possible for quantum technology to fulfill its promise of revolutionizing computing, communication, and sensing. However, the advent of the Noisy Intermediate-Scale Quantum (NISQ) era forces us to investigate dissipation and decoherence and to find ways to utilize them effectively. This talk aims to provide examples where interactions with the environment play a pivotal role in generating and detecting collective quantum phenomena, inspiring new perspectives on harnessing environment interactions for advancing quantum technologies. Firstly, we will delve into the emerging field of topological quantum synchronization, a novel form of synchronization where topology and dissipation intertwine to protect synchronized dynamics against perturbation. Next, we will explore how carefully tailored interactions with the environment induce energy migration within small quantum spin networks characterized by a superradiant speed-up, demonstrating the potential for utilizing dissipation as a resource rather than a hindrance. Finally, if time permits, I will introduce a novel methodology for probing quantum criticality in non-equilibrium systems. This method circumvents the shortcomings of standard perturbative expansions, enabling a comprehensive and thermodynamically consistent understanding of critical phenomena in systems coupled to non-Markovian reservoirs.

Georg Engelhardt

Southern University of Science and Technology in the Shenzhen Institute of Quantum Science and Engineering

Photon-Resolved Floquet Theory and its application to quantum sensing

When: 12:00-13:00 CET, April 11th (Thursday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

Quantum sensing uses quantum properties of matter to enhance the sensitivity in precision measurements. Besides others, it already finds important applications in atomic clocks, for medical purposes, and in the search for dark matter. Many currently employed quantum sensing protocols exhibit a simple setup, in which a laser probes the optical properties of an ensemble of atoms, molecules, or other quantum emitters, which are subject to the external stimulus to be measured. An important figure of merit to predict the sensitivity is the signal-to-noise ratio.  While it is easy to theoretically calculate the signal, the accurate prediction of the noise is challenging.

Motivated by this, we have developed the Photon-Resolved Floquet Theory (PRFT), which besides predicting the state of a driven quantum system (e.g., the atom or molecule), can also predict the number of photons exchanged with the coherent driving field [1,2]. To this end, the PRFT introduces counting fields into the semiclassical equations of motions, that track the photons in the driving field.  Interestingly, the PRFT predicts light-matter entanglement in the Floquet-state basis. This effect can be employed to devise a measurement-based quantum communication protocol, which has favorable scaling properties over long distances.  We apply the PRFT to spectroscopy, where it can predict the Fisher information of coherent spectroscopic signals [3]. The PRFT thus opens new paths to design and optimize quantum sensors based on AMO systems, which might assist in the discovery of new physics.

[1] G. Engelhardt, S. Choudhury, and W. V. Liu, Phys. Rev. Research 6, 013116 (2024)

[2] G. Engelhardt, JY. Luo, V. M. Bastidas, and G. Platero, arXiv: 2311.01509

[3] G. Engelhardt et al., in preparation

Paloma A. Huidobro 

Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid

Light and photons in time varying media

When: 12:00-13:00 CET, March 21st (Thursday), 2024

Where: Salon de Actos, ICMM-CSIC, Campus de Cantoblanco, Madrid

In this talk I will first introduce the basic concepts of wave interactions in time varying media. I will discuss how temporal modulations of the optical parameters offer new pathways in light control, as energy is not necessarily conserved in these time-dependent systems, and non-reciprocal effects can be realized [1]. I will concentrate on a class of space-time modulations where parameters are modulated in a travelling-wave form, such that there is an apparent motion of the optical properties, and discuss light propagation in these systems: from non-reciprocal effects even in the quasistatic limit, to synthetic motion and the link to the Fresnel drag effect of light in moving media, through an unconventional linear gain mechanism.

Next, I will discuss photon pair creation and squeezing in a photonic time crystal, the temporal counterpart of a conventional photonic crystal. I will show how modulating the refractive index in time causes dynamical Casimir processes, in which pairs of photons can be created. However, when there are multiple time interfaces, these photon pair creation phenomena depend dramatically on the photon’s wavelength, as well as on the contrast between the refractive indices, the duration of each temporal period and the number of periods that form the photonic time crystal [2].

 References:

[1] Galiffi, E., Tirole, R., Yin, S., Lia, H., Vezzoli, S., Huidobro, P.A., Silveirinha, M.G., Sapienza, R., Alu, A., and Pendry, J.B. “Photonics of time varying media” Advanced Photonics, 4(1), 014002 (2022)

[2] Echave, J., García-Vidal, F.J., &  Huidobro, P.A., “Photon squeezing in time varying media”, to be submitted (2024)

Belén Valenzuela

ICMM-CSIC, Madrid, Spain

A toy Landau model for illustrating learning and unlearning of nociplastic pain

When: 12:00-13:00 CET, March 3rd, 2024

Where: Salon de Actos, ICMM-CSIC, Campus de Cantoblanco, Madrid

Chronic pain is increasing at an alarming rate specially among young people and kids. This disturbing situation has increased the research interest in gaining a deeper understanding of chronic pain. Physiologically, nociplastic pain has been defined as a significant component of chronic pain not linked to tisular damage but to a nocive plasticity pattern of the nervous and immune system. From phenomenological cognitive sciences, there is compelling evidence that the consolidation of nociplastic pain is a complex, nonconscious learned process of threat perception that gives rise to maladaptive loops. Embodied neurobiological pain education is emerging as a promising approach to reduce the perception of threat which leads to a decrease of symptom intensity and frequency, improved functionality and eventual symptom alleviation. However, this approach is not well known among clinicians and society at large, creating a communication problem that unfortunately perpetuates the suffering of the patients. We propose a toy Landau model to describe the learning and unlearning process of nociplastic pain, aiming to clarify this complex situation and facilitate communication across different sectors of society. Nociplastic pain corresponds to a first-order transition, with attention more likely in the alert-protection state than in the trust-explore state. Two appealing results of the model are that the perception of the critical context depends on personal history regarding the symptom and that maladaptive loops are formed when there is alarming learned historical information about the symptom, along with confused and contradictory expert information, as seen in nocebo messages. Learning and unlearning in the model correspond to a change in control parameters that can weight more the alert-protection state, the trust-explore state, the uncertain state or the neutral state. This description clarifies why neurobiological education is the ground therapy from which others must be built to embody the accesible, clear, and trustworthy information. The model could be used to address other mind-body syndromes.

YouTube link: https://www.youtube.com/watch?v=i7mHqDFsc_4