Latest Papers in Condensed Matter Physics
Mesoscale And Nanoscale Physics
Microscopyc description of the Photothermal increase of temperature for metallic nanoparticles excited with short-laser pulses (1904.02109v1)
M. Rodríguez-Matus, C. Garcia-Segundo, Jean-Parick Connerade
2019-04-03
The pulsed photothermal phenomenon due to optically absorbed energy, result from non-radiative decay mechanisms, which in nature, these imply the temporal change in the local free energy and thus a temporary change in the local temperature. At the nanoscale, this is a prediction broadly described in terms of macroscopic variables. Here we introduce a formalism based on the Jarzynski's physical statistics description, for interpreting the equilibrium free energy difference between two configurations of a metallic nanoparticle. In this way, within a finite-time span, we describe the temporal increase of the local free energy and thus of the local temperature arising from temporarily bringing the sample far from thermal equilibrium. The result is an expression for which one can get the photothermally induced change of temperature for a metallic nanoparticle. For practical purposes, we limited the study to Au nanoparticles. The study is made as function of the particle size and the optical properties for wavelengths spanning the optical range. The assessment indicates that, for nanoparticles with radii shorter than 40 nm, the temperature change is strongly dependent on particle size and on the illumination wavelength. While, for near 40 nm particle radii, the current description and the known formalism, based on macroscopic variables, predict the very same temperature change. At the closing we discuss additional possible thermodynamic consequences associated to the scale considerations.
Strong plasmon-molecule coupling at the nanoscale revealed by first-principles modeling (1904.02097v1)
Tuomas P. Rossi, Timur Shegai, Paul Erhart, Tomasz J. Antosiewicz
2019-04-03
Strong light-matter interactions in both the single-emitter and collective strong coupling regimes attract significant attention due to emerging quantum and nonlinear optics applications, as well as opportunities for modifying material-related properties. Further exploration of these phenomena requires an appropriate theoretical methodology, which is demanding since polaritons are at the intersection between quantum optics, solid state physics and quantum chemistry. Fortunately, however, nanoscale polaritons can be realized in small plasmon-molecule systems, which in principle allows treating them using ab initio methods, although this has not been demonstrated to date. Here, we show that time-dependent density-functional theory (TDDFT) calculations can access the physics of nanoscale plasmon-molecule hybrids and predict vacuum Rabi splitting in a system comprising a few-hundred-atom aluminum nanoparticle interacting with one or several benzene molecules. We show that the cavity quantum electrodynamics approach holds down to resonators on the order of a few cubic nanometers, yielding a single-molecule coupling strength exceeding 200 meV due to a massive vacuum field value of 4.5 V/nm. In a broader perspective, our approach enables parameter-free in-depth studies of polaritonic systems, including ground state, chemical and thermodynamic modifications of the molecules in the strong-coupling regime, which may find important use in emerging applications such as cavity enhanced catalysis.
Revisiting (higher order and crystalline) topology in old models of lead telluride (1812.09330v2)
Iñigo Robredo, Maia G. Vergniory, Barry Bradlyn
2018-12-21
In this work, we revisit the model of PbTe presented in [E. Fradkin, E. Dagotto, and D. Boyanovsky, Phys. Rev. Lett. 57, 2967 (1986)]. We show that the low energy theory of this model corresponds to a (higher-order) topological crystalline insulator in space group
, diagnosable by symmetry indicators. We show that the gapless fermions found on antiphase domain walls are the topological boundary modes of the system, due to a nonvanishing mirror Chern number. Furthermore, we show that any symmetric completion of the model must be in this same topological phase. Finally, we comment on the relationship of this model to realistic PbTe, which has recently been predicted to have a phase which realizes same bulk symmetry indicators.
Bulk-edge correspondence and long range hopping in the topological plasmonic chain (1902.00467v2)
Simon R. Pocock, Paloma A. Huidobro, Vincenzo Giannini
2019-02-01
The existence of topologically protected edge modes is often cited as a highly desirable trait of topological insulators. However, these edge states are not always present. A realistic physical treatment of long range hopping in a one-dimensional dipolar system can break the symmetry that protects the edge modes without affecting the bulk topological number, leading to a breakdown in bulk-edge correspondence. It is important to find a better understanding of where and how this occurs, as well as how to measure it. Here we examine the behaviour of the bulk and edge modes in a dimerised chain of metallic nanoparticles and in a simpler non-Hermitian next-nearest-neighbour model to provide some insight into the phenomena of bulk-edge breakdown. We construct bulk-edge correspondence phase diagrams for the simpler case and use these ideas to devise a measure of symmetry-breaking for the plasmonic system based on its bulk properties. This provides a parameter regime for which bulk-edge correspondence is preserved in the topological plasmonic chain, as well as a framework for assessing this phenomenon in other systems.
Large enhancement of conductivity in Weyl semimetals with tilted cones: pseudo-relativity and linear response (1903.09081v2)
Saber Rostamzadeh, İnanç Adagideli, M. O. Goerbig
2019-03-21
We study the conductivity of two-dimensional graphene-type materials with tilted cones as well as their three-dimensional Weyl counterparts and show that a covariant quantum Boltzmann equation is capable of providing an accurate description of these materials' transport properties. The validity of the covariant Boltzmann approach is corroborated by calculations within the Kubo formula. We find a strong anisotropy in the conductivities parallel and perpendicular to the tilt direction upon increase of the tilt parameter
, which can be interpreted as the boost parameter of a Lorentz transformation. While the ratio between the two conductivities is
in the two-dimensional case where only the conductivity perpendicular to the tilt direction diverges for
, both conductivities diverge in three-dimensional Weyl semimetals, where
separates a type-I (for
) from a type-II Weyl semimetal (for
).
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