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At low-temperatures a gas of bosons will undergo a phase transition into a quantum state of matter known as a Bose-Einstein condensate (BEC), in which a large fraction of the particles will occupy the ground state simultaneously. Here we explore the performance of an endoreversible Otto cycle operating with a harmonically confined Bose gas as the working medium. We analyze the engine operation in three regimes, with the working medium in the BEC phase, in the gas phase, and driven across the BEC transition during each cycle. We find that the unique properties of the BEC phase allow for enhanced engine performance, including increased power output and higher efficiency at maximum power., Comment: 23 pages, 6 figures

We explore proximity-induced magnetocaloric effect (MCE) on transition metal dichalcogenides, focusing on a two-dimensional (2D) MoTe$_2$ monolayer deposited on a ferromagnetic semiconductor EuO substrate connected to a heat source. We model this heterostructure using a tight-binding model, incorporating exchange and Rashba fields induced by proximity to EuO, and including temperature through Fermi statistics. The MCE is induced on the 2D MoTe$_2$ layer due to the EuO substrate, revealing large spin-polarized entropy changes for energies out of the band gap of the MoTe$_2$-EuO system. By gating the chemical potential, the MCE can be tuned to produce heating for spin up and cooling for spin down across the $K$ and $K'$ valley splitting in the valence band, whereas either heats or cools for both spins in the conduction band. The Rashba field enhances the MCE in the valence zone while decreasing it in the conduction bands. The exchange field-induced MCE could be useful to produce tunable spin-polarized thermal responses in magnetic proximitized 2D materials., Comment: 6 pages, 5 figures

We theoretically study the thermoelectric transport properties of strained HgTe in the topological insulator phase. We developed a model for the system using a Dirac Hamiltonian including the effect of strain induced by the interface between HgTe and the CdTe substrate. The conductivity tensor was explored assuming the electrons are scattered by charge impurities, while the thermopower tensor was addressed using the Mott relation. Seebeck and Nernst responses exhibit remarkable enhancements in comparison with other two-dimensional Dirac materials, such as graphene, germanane, prosphorene and stanene. The intensity of these termoeletric responses, their dependencies with the external perpendicular magnetic field and temperature are also addressed.

Structure-based Deep Fusion models were recently shown to outperform several physics- and machine learning-based protein-ligand binding affinity prediction methods. As part of a multi-institutional COVID-19 pandemic response, over 500 million small molecules were computationally screened against four protein structures from the novel coronavirus (SARS-CoV-2), which causes COVID-19. Three enhancements to Deep Fusion were made in order to evaluate more than 5 billion docked poses on SARS-CoV-2 protein targets. First, the Deep Fusion concept was refined by formulating the architecture as one, coherently backpropagated model (Coherent Fusion) to improve binding-affinity prediction accuracy. Secondly, the model was trained using a distributed, genetic hyper-parameter optimization. Finally, a scalable, high-throughput screening capability was developed to maximize the number of ligands evaluated and expedite the path to experimental evaluation. In this work, we present both the methods developed for machine learning-based high-throughput screening and results from using our computational pipeline to find SARS-CoV-2 inhibitors.

The electrocaloric (EC) effect is the reversible change in temperature and/or entropy of a material when it is subjected to an adiabatic electric field change. Our tight-binding calculations linked to Fermi statistics, show that the EC effect is sensitive to the stacking arrangement in trilayer graphene (TLG) structures connected to a heat source, and is produced by changes of the electronic density of states (DOS) near the Fermi level when external gate fields are applied on the outer graphene layers. We demonstrate the AAA-stacked TLG presents an inverse EC response (cooling), whereas the EC effect in ABC-stacked TLG remains direct (heating) regardless of the applied gate field potential strength. We reveal otherwise the TLG with Bernal-ABA stacking geometry generates both the inverse and direct EC response in the same sample, associated with a gate-dependent electronic entropy transition at finite temperature. By varying the chemical potential to different Fermi levels, we find maxima and minima of the DOS are located near the extremes of the electronic entropy, which are correlated with sign changes in the differential entropy per particle, giving a particular experimentally measurable electronic entropy spectrum for each TLG geometry. The EC effect in quantum two-dimensional layered systems may bring a wide variety of prototype van der Waals materials that could be used as versatile platforms to controlling the temperature in nanoscale electronic devices required in modern portable on-chip technologies., Comment: 11 pages, 10 figures

In this paper, we analyze the total work extracted and the efficiency of the magnetic Otto cycle in its classic and quantum versions. As a general result, we found that the work and efficiency of the classical engine is always greater than or equal to that of its quantum counterpart independent of the working substance. In the classical case, this is due to the fact that the working substance is always in thermodynamic equilibrium at each point of the cycle, maximizing the energy extracted in the adiabatic paths. We apply this analysis to the case of a two-level system, finding that the work and efficiency in Otto's quantum and classical cycle are identical, regardless of the working substance, and we obtain similar results for a multilevel system where a linear relationship between the spectrum of energies of the working substance and the external magnetic field is fulfilled. Finally, we show an example of a three-level system in which we compare two zones in the entropy, temperature and magnetic field diagram to find which is the most efficient when performing a thermodynamic cycle. This work provides a practical way to look for temperature and magnetic field zones in the entropy diagram that can maximize the power extracted from Otto's magnetic engine.