In this talk I will present an approach to describe the thermodynamic properties of nonequilibrium quantum systems at the nanoscale. One of the main difficulties of this kind of study – both at the classical and at the quantum level – is that such systems do not have a large number of constituents and, therefore, do not  satisfy one of the fundamental premises of microscopic theories that describe thermodynamic relationships. Another central problem is associated with the difficulty of making a distinction between the “system”, the “bath” and its “interfaces” in very tiny objects. I will discuss how to deal with these problems using the Landauer-Büttiker approach for the calculation of the entropy production in electronic transport. The latter reproduces the results of standard thermoelectric theories as well as approaches based on information theory,  besides allowing to calculate entropy fluctuations and study the newly proposed thermodynamic uncertainty relations (TUR). If time allows, I will show how the formalism can be extended to time-dependent systems, an essential element for understanding quantum engines.

Liquids are often considered an aggressive medium for standard electronics due to strong polarization effects and electrolysis [1]. However, they can turn advantageous, for example, to operate thin-film transistors (TFT) in the so-called solution-gated architecture [1-4]. In such devices, a drop of water, saline solution, or ionic liquid replaces the dielectric layer of regular TFTs, and an immersed gate electrode controls the device channel via the electrostatic coupling between ions and the semiconductor charge carriers [1–4]. In this talk, we will present the basics of solution-gated transistors, viz. types of device architecture, how to fabricate and operate them. We will discuss how such device platform can be used to electrically characterize thin films made of molecular/organic semiconductors and 2D materials (viz. liquid-phase exfoliated MoS2).
Finally, we will show how such devices can be used as powerful electrical transducers to develop chemical sensors and biosensors.

[1] T. Cramer, et al., J. Mater. Chem. B. 1, p. 3728–3741 (2013).
[2] R.F. de Oliveira, et al., Org. Electron. 31, p. 217–226 (2016).
[3] R. F. de Oliveira, et al., Adv. Func. Mater. 29, 1905375 (2019).
[4] F. Torricelli, et al., Nat. Rev. Methods Primers 1, 66 (2021).    

In the seminar, I would like to discuss the use of III-V semiconductor membranes as buildingblocks in nanotechnology by reviewing the fundamentals like the fabrication and basicproperties of membrane-based rolled-up tubes as well as flat membranes. Highlighting a recentexample, the influence of strain to the optical properties of rolled-up heterostructures has been investigated combining x-ray diffraction with photoluminescence spectroscopy and theoreticalcalculations. In the work, we have shown that not only a detailed understanding of the strain isnecessary to predict optical properties, but also that rolled-up tubes can be used to engineerthese properties in an elegant way. Moving away from three-dimensional structures formed by the release and rearrangement ofIII-V semiconductor membranes, I will briefly discuss the formation and application oftwo-dimensional, released III-V semiconductor membranes. Here, I would like to emphasize theuse as compliant or virtual substrates. For III-V membranes, we have demonstrated how such amembrane substrate influences the epitaxy of heterostructures. Moreover, we have proven thatoptical active structures can be grown on membranes and the emission is tunable by themembrane used as a virtual substrate.

References:
[1] N. Rodrigues, Leonarde; Scolfaro, Diego; Da Conceição, Lucas; Malachias, Angelo; Couto, Odilon D. D.; Iikawa, Fernando; Deneke, Christoph. Rolled-up Quantum Wells Composed of Nanolayered InGaAs/GaAs Heterostructures as Optical Materials for Quantum Information  Technology. ACS Applied Nano Materials, v. 4, p. 3140-3147, 2021.

[2] Garcia Jr., Ailton; Rodrigues, Leonarde N.; Covre da Silva, Saimon Felipe; Morelhão,  Sergio L.;Couto Jr., Odilon D. D.; Iikawa, Fernando; Deneke, Christoph. In-place bonded semiconductormembranes as compliant substrates for III-V compound devices. 
Nanoscale, v. 11, p. 3748, 2019.   

The journey and the entanglements intend to address what once the physicist John Ziman warned us about: "SCIENTISTS know philosophy and sociology as fish know water. They understand instinctively how to live in it without being aware that they are doing so.  That is, until the fish bowl is stirred or (horror!) overturned. We seem to be living in just such a time. Science is being shaken up and forced to abandon many of its cherished customs. We need to think hard about what is happening and what we should do, not merely to survive but to serve and delight humanity".   

Manganese oxides are of great scientific and technological relevance due to their wide range applications in catalysis, battery materials candidates, electrochemical electrodes, among others. Their properties are related to MnOx compounds chemistry-phase relationship to contain labile lattice oxygen and a particular density of Mn cations in a given oxidation state. For this reason, the growth of manganese oxides thin films on well-defined metal substrates has been widely explored in the literature. For this end, in this talk, I will discuss our own experimental findings on MnOx thin film growth on an Au(111) and Cu(111) substrates over a wide range of preparation conditions and film thicknesses investigated mainly by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). We will discuss the formation of MnO and Mn3O4 oxide phase and structure, and the possible consequences to its electronic properties depending on the film surface orientation and substrate.

In the age of international super-collaborations, like LIGO, ESO, and neutrino telescopes and detectors, the LHC (Large Hadron Collider) is the large and complex proton-beans-collider with the mission of facing the challenges posed by advancing matter structure comprehension at the femto- and atto-scale. Its third round, forecast to start in March 2022, will launch an eighth experiment, FASER, which will join the ongoing Collaborations ALICE, ATLAS, CMS, LHCb, LHCf, MoEDAL and TOTEM.
    In this seminar, we will present the general structure of the primordial Universe phase transitions, the general frame of the Standard-Model of Fundamental Interactions (SM), and its 23 limiting problems. Starting from there, we will discuss the search for the so-called “New Physics” and how the LHC has confirmed theoretical results of the SM, revealing new categories of hadrons (tetra- and pentaquarks) and suggesting the existence of new particles and complex structures – to be probed more deeply in Run-3 – that were formed in physical conditions close to those in the ages of the great phase transitions, which gave origin to the SM physics. 

I will discuss the non-equilibrium dynamics in interacting systems subjected to quantum quenches. In such a process, a system is prepared in the ground state of a given Hamiltonian, we then introduce a sudden change in the system and let it evolves in time according to a new Hamiltonian. In the talk, I will introduce this subject and then exemplify it with results obtained in my group. 

In a first case [1], we connect two spin-1/2 XXZ chains prepared in different phases, one in the ferromagnetic phase and the other in the critical (Luttinger) phase. We show that the on-site magnetization and bipartite entanglement entropy follow effective light cones after the quench, which are determined by different types of excitations depending on the system parameters.

In a second case [2], a magnetic impurity is suddenly coupled to interacting chains. We find that the local magnetization at the impurity site decays faster if we increase the electronic interaction in the chains, even though the spin velocity decreases. At intermediate timescales, we obtain insights into the time evolution of the Kondo screening cloud in interacting systems.

[1] A. L. de Paula et al., Physical Review B 95, 045125 (2017).
[2] Helena Bragança et al., Physical Review B 103, 125152 (2021).

In this talk we will discuss atomic frustrated states in diatomic molecules hosted by the bilayer graphene setup twisted by the first magic angle and with broken inversion symmetry in the Dirac cones of the system mini-Brillouin zones. Such states show local spectral features typically from uncoupled atoms, but counterintuitively, they also exhibit nonlocal molecular correlations, which turn them into atomically frustrated. By considering a particle-hole symmetric molecule in the Moiré superlattice length-scale, distinctly from the metallic Weyl counterparts, a molecular zero mode atomically frustrated at the spectral densities of the dimer’s atoms, is then revealed. To this end, a strong metallic phase with a plateau in the density of states established by the broken inversion symmetry, together with pronounced blue and red shifts in the molecular levels, due to the magic angle condition, should occur synergistically with atomic Coulomb correlations. Consequently, an entire collapse of these molecular peaks into a single one atomically frustrated, taking place exactly at the Fermi energy, becomes feasible just by tuning properly opposite gate voltages attached to the graphene monolayers. Therefore, unusual molecular bindings are proposed via the twistronics of the bilayer graphene system, in particular, if its metallic phase is fully established.

In the last decades, several 2D materials (e.g., graphene, hexagonal boron nitride, transition metal dichalcogenides, artificial organometallic networks - MOFs) have been intensively studied, revealing interesting physical phenomena and unique electronic, optical, and mechanical properties. These materials are promising for innovative technological applications, such as new catalysts, sensors, electronic and photonic devices, magnetic networks, etc. A fascinating technique for preparing these materials is the so-called on-surface synthesis (SS) [1,2]. SS is a bottom-up technique that uses specifically “designed” precursors as molecular building blocks (such as pieces of a LEGO) to create, on-demand, new materials with the desired atomic and electronic structure. With this, we can, for example, build model systems (toy models) that allow exploring singular properties, such as new semiconductors, photonic lattices, or artificial magnetic lattices.

The Surface Physics Group (GFS) at UNICAMP has used SS in recent years in the epitaxial growth of different members of these 2D material families [3-8]. In this seminar, I will show recent examples in which we apply different growth and functionalization strategies to produce new semiconductors [7] and organometallic networks [3-5,8], whose electronic and atomic structures have been characterized by X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy/spectroscopy (STM/STS) techniques.

References:

[1] Mengqi Zeng, et al., Chemical Reviews 118 (13), 6236-6296 (2018).

[2] Sylvain Clair, et al., Chem. Rev. 119, 4717-4776 (2019).

[3] M. Lepper et al., Angew. Chem. Int. Ed.. 57, 10074-10079 (2018).

[4] Juan Carlos Moreno-López, et al., Chemistry of Materials 31 (8), 3009-3017 (2019).

[5] Alisson Ceccatto dos Santos, et al., Chemistry of Materials 32 (5), 2114-2122 (2020).

[6] Gabriela Moura do Amaral, et al., Applied Surface Science, 538,148138 (2021).

[7] Nataly Herrera-Reinoza, et al., Chemistry of Materials 33, 2871-2882 (2021).

[8] Alisson Ceccatto dos Santos, et al., J. Phys. Chem. C 125, 31, 17164–17173 (2021).

Abstract: Determining the dynamics of the expectation values of operators acting on quantum many-body systems is a challenging task. Matrix product states (MPS) have traditionally been the ”go-to” models for these systems because calculating expectation values in this representation can be done with relative simplicity and high accuracy. However, such calculations can become computationally costly when extended to long times. Here, we present a solution for extending the computation of expectation values to long time intervals. We utilize a convolutional neural network model as a tool for the extended prediction of MPS generated expectation values calculated within the regime of short time intervals. With this model, the computational cost of generating long-time dynamics is significantly reduced, while maintaining reasonable accuracy. These results are demonstrated with operators relevant to quantum spin models in one spatial dimension.