arXiv subjects

Eduardo Flores

Publications and source records attributed to Eduardo Flores.

18 recordsLinked to original sources

arXiv2026

Low Energy Neutrinos in Milky Way and Cloud-9

We study low-energy galactic neutrinos in the Milky Way under two descriptions of gravity and show that they can prove gravity underlying nature. If gravity is quantum, its long-range interaction produces an atom-like bound neutrino structure. However, we find that withing 292 kpc, this structure contributes only 10 to the -29 of the galaxy dark matter, ruling it out as a deark-matter candidate. Its detection would nevertheless provide direct evidence for quantum gravity mediated by gravitons. If gravity instead arises from spacetime curvature, neutrinos interact only through the short-range weak force and behave as free, collisionless classical particles orbiting the galaxy. In this regime, they do not experience Fermi pressure and can form a sufficiently compact population to reproduce the Milky Way rotation curve. We further model Cloud-9 dark-matter compoent as free, collisionless neutrinos. Because neutrino-antinetrino annihilation cross section is extremely small, neutrinos and antineutrinos may remai near equilibrium over cosmological timescales, potentially relating this framework to the observed matter-antimatter assymmetry.

hep-ph↗

arXiv2023

Casimir force in discrete scalar fields I: 1D and 2D cases

We calculate the Casimir force between parallel plates for a massless scalar field. When adding the energy of normal modes, we avoid infinities by using a discrete spacetime lattice; however, this approach proves ineffective as long as both space and time are kept discrete. Yet, when time is treated as continuous while the scalar field forms a spatial periodic lattice, our method succeeds, and we refer to this approach as Hamiltonian lattice theory. The dispersion relation for both square and triangular lattices accurately reproduces the subtle Casimir effect, providing evidence that the Casimir force is independent of the type of lattice used. At low frequencies, both lattices exhibit a high level of rotational symmetry. However, at high frequencies, they lose this symmetry, even though the propagation of high-frequency waves becomes limited as their group velocity approaches zero.

quant-ph↗

arXiv2021

Integrating van der Waals materials on paper substrates for electrical and optical applications

Paper holds the promise to replace silicon substrates in applications like internet of things or disposable electronics that require ultra-low-cost electronic components and an environmentally friendly electronic waste management. In the last years, spurred by the abovementioned properties of paper as a substrate and the exceptional electronic, mechanical and optical properties of van der Waals (vdW) materials, many research groups have worked towards the integration of vdW materials-based devices on paper. Recently, a method to deposit a continuous film of densely packed interconnects of vdW materials on paper by simply rubbing the vdW crystals against the rough surface of paper has been presented. This method utilizes the weak interlayer vdW interactions and allows cleaving of the crystals into micro platelets through the abrasion against the paper. Here, we aim to illustrate the general character and the potential of this technique by fabricating films of 39 different vdW materials (including superconductors, semi-metals, semiconductors, and insulators) on standard copier paper. We have thoroughly characterized their optical properties showing their high optical quality: one can easily resolve the absorption band edge of semiconducting vdW materials and even the excitonic features present in some vdW materials with high exciton binding energy. We also measured the electrical resistivity for several vdW materials films on paper finding exceptionally low values, which are in some cases, orders of magnitude lower than those reported for analogous films produced by inkjet printing. We finally demonstrate the fabrication of field-effect devices with vdW materials on paper using the paper substrate as an ionic gate.

cond-mat.mtrl-sci↗

arXiv2020

Raman Fingerprint of Pressure-Induced Phase Transitions in TiS3 Nanoribbons: Implications for Thermal Measurements under Extreme Stress Conditions

Two-dimensional layered trichalcogenide materials have recently attracted the attention of the scientific community because of its robust mechanical, thermal properties and applications in opto and nanoelectronics devices. We report the pressure dependence of out-of plane Ag Raman modes in high quality few-layers titanium trisulfide (TiS3) nanoribbons grown using a direct solid-gas reaction method and infer their cross-plane thermal expansion coefficient.Both mechanical stability and thermal properties of the TiS3 nanoribbons are elucidated using phonon-spectrum analyses. Raman spectroscopic studies at high pressure (up to 34 GPa) using a diamond anvil cell identify four prominent Ag Raman bands; a band at 557 cm-1 softens under compression, and others at 175, 300, and 370 cm-1 show normal hardening. Anomalies in phonon mode frequencies and excessive broadening in line-width of the soft phonon about ~ 13 GPa are attributed to the possible onset of a reversible structural transition. A complete structural phase transition at 43 GPa is inferred from Ag soft mode frequency (557 cm-1) versus pressure extrapolation curve, consistent with recent reported theoretical predictions. Using the experimental mode Grüneisen parameters i of Raman modes, the cross-plane thermal expansion coefficient Cv of the TiS3 nanoribbons at ambient phase is estimated to be1.32110-6K-1. The observed results are expected to be useful in calibration and performance of next generation nano-electronics and optical devices under extreme stress conditions.

cond-mat.mtrl-sci↗

arXiv2020

Large birefringence and linear dichroism in TiS3 nanosheets

TiS3 nanosheets have proven to be promising candidates for ultrathin optoelectronic devices due to their direct narrow band-gap and the strong light-matter interaction. In addition, the marked in-plane anisotropy of TiS3 is appealing for the fabrication of polarization sensitive optoelectronic devices. Herein, we study the optical contrast of TiS3 nanosheets of variable thickness on SiO2/Si substrates, from which we obtain the complex refractive index in the visible spectrum. We find that TiS3 exhibits very large birefringence, larger than that of well-known strong birefringent materials like TiO2 or calcite, and linear dichroism. These findings are in qualitative agreement with ab initio calculations that suggest an excitonic origin for the birefringence and linear dichroism of the material.

cond-mat.mtrl-sci↗

arXiv2020

Polarization-sensitive and broadband photodetection based on a mixed-dimensionality TiS3/Si p-n junction

The capability to detect the polarization state of light is crucial in many day-life applications and scientific disciplines. Novel anisotropic two-dimensional materials such as TiS3 combine polarization sensitivity, given by the in-plane optical anisotropy, with excellent electrical properties. Here we demonstrate the fabrication of a monolithic polarization sensitive broadband photodetector based on a mixed-dimensionality TiS3/Si p-n junction. The fabricated devices show broadband responsivity up to 1050 nm, a strong sensitivity to linearly polarized illumination with difference between the two orthogonal polarization states up to 350 % and a good detectivity and fast response time. The discussed devices can be used as building blocks to fabricate more complex polarization sensitive systems such as polarimeters.

physics.app-ph↗

arXiv2020

Tunable Photodetectors via in situ Thermal Conversion of TiS$_3$ to TiO$_2$

In two-dimensional materials research, oxidation is usually considered as a common source for the degradation of electronic and optoelectronic devices or even device failure. However, in some cases a controlled oxidation can open the possibility to widely tune the band structure of 2D materials. In particular, we demonstrate the controlled oxidation of titanium trisulfide (TiS$_3$), a layered semiconductor that has attracted much attention recently thanks to its quasi-1D electronic and optoelectronic properties and its direct bandgap of 1.1 eV. Heating TiS$_3$ in air above 300 °C gradually converts it into TiO$_2$, a semiconductor with a wide bandgap of 3.2 eV with ap-plications in photo-electrochemistry and catalysis. In this work, we investigate the controlled thermal oxidation of individual TiS$_3$ nanoribbons and its influence on the optoelectronic properties of TiS$_3$-based photodetectors. We observe a step-wise change in the cut-off wavelength from its pristine value ~1000 nm to 450 nm after subjecting the TiS$_3$ devices to subsequent thermal treatment cycles. Ab-initio and many-body calculations confirm an increase in the bandgap of titanium oxysulfide (TiO$_{2-x}$S$_x$) when increasing the amount of oxygen and reducing the amount of sulfur.

physics.app-ph↗

arXiv2020

Multi-terminal electronic transport in boron nitride encapsulated TiS$_3$ nanosheets

We have studied electrical transport as a function of carrier density, temperature and bias in multi-terminal devices consisting of hexagonal boron nitride (h-BN) encapsulated titanium trisulfide (TiS$_3$) sheets. Through the encapsulation with h-BN, we observe metallic behavior and high electron mobilities. Below $\sim$60 K an increase in the resistance, and non-linear transport with plateau-like features in the differential resistance are present, in line with the expected charge density wave (CDW) formation. Importantly, the critical temperature and the threshold field of the CDW phase can be controlled through the back-gate.

cond-mat.mtrl-sci↗

arXiv2019

Chemical Vapor Deposition Growth of Boron-Carbon-Nitrogen layers from Methylamine Borane Thermolysis Products

This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and Graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar composition.

cond-mat.mtrl-sci↗

arXiv2017

Electronics and optoelectronics of quasi-one dimensional layered transition metal trichalcogenides

The isolation of graphene and transition metal dichalcongenides has opened a veritable world to a great number of layered materials which can be exfoliated, manipulated, and stacked or combined at will. With continued explorations expanding to include other layered materials with unique attributes, it is becoming clear that no one material will fill all the post-silicon era requirements. Here we review the properties and applications of layered, quasi-one dimensional transition metal trichalcogenides (TMTCs) as novel materials for next generation electronics and optoelectronics. The TMTCs present a unique chain-like structure which gives the materials their quasi-one dimensional properties such as high anisotropy ratios in conductivity and linear dichroism. The range of band gaps spanned by this class of materials (0.2 eV- 2 eV) makes them suitable for a wide variety of applications including field-effect transistors, infrared, visible and ultraviolet photodetectors, and unique applications related to their anisotropic properties which opens another degree of freedom in the development of next generation electronics. In this review we survey the historical development of these remarkable materials with an emphasis on the recent activity generated by the isolation and characterization of atomically thin titanium trisulfide (TiS3).

cond-mat.mtrl-sci↗

arXiv2017

High current density electrical breakdown of TiS3 nanoribbon-based field-effect transistors

The high field transport characteristics of nanostructured transistors based on layered materials are not only important from a device physics perspective but also for possible applications in next generation electronics. With the growing promise of layered materials as replacements to conventional silicon technology, we study here the high current density properties of the layered material titanium trisulfide (TiS3). We observe high breakdown current densities up to 1.7 10^6 A/cm^2 in TiS3 nanoribbon-based field-effect transistors which are among the highest found in semiconducting nanomaterials. Investigating the mechanisms responsible for current breakdown, we perform a thermogravimetric analysis of bulk TiS3 and compare the results with density functional theory (DFT) and Kinetic Monte Carlo calculations. We conclude that oxidation of TiS3 and subsequent desorption of sulfur atoms plays an important role in the electrical breakdown of the material in ambient conditions. Our results show that TiS3 is an attractive material for high power applications and lend insight to the thermal and defect activated mechanisms responsible for electrical breakdown in nanostructured devices.

cond-mat.mes-hall↗

arXiv2015

Temperature dependent Raman spectroscopy of titanium trisulfide (TiS3) nanoribbons and nanosheets

Titanium trisulfide (TiS3) has recently attracted the interest of the 2D community as it presents a direct bandgap of ~1.0 eV, shows remarkable photoresponse, and has a predicted carrier mobility up to 10000 cm2V-1 s-1. However, a study of the vibrational properties of TiS3, relevant to understanding the electron-phonon interaction which can be the main mechanism limiting the charge carrier mobility, is still lacking. In this work, we take the first steps to study the vibrational properties of TiS3 through temperature dependent Raman spectroscopy measurements of TiS3 nanoribbons and nanosheets. Our investigation shows that all the Raman modes linearly soften (red shift) as the temperature increases from 88 K to 570 K, due to the anharmonic vibrations of the lattice which also includes contributions from the lattice thermal expansion. This softening with the temperature of the TiS3 modes is more pronounced than that observed in other 2D semiconductors such as MoS2, MoSe2, WSe2 or black phosphorus (BP). This marked temperature dependence of the Raman could be exploited to determine the temperature of TiS3 nanodevices by using Raman spectroscopy as a non-invasive and local thermal probe. Interestingly, the TiS3 nanosheets show a stronger temperature dependence of the Raman modes than the nanoribbons, which we attribute to a lower interlayer coupling in the nanosheets.

cond-mat.mes-hall↗

arXiv2015

Electronic bandgap and exciton binding energy of layered semiconductor TiS3

We present a study of the electronic and optical bandgap in layered TiS3, an almost unexplored semiconductor that has attracted recent attention because of its large carrier mobility and inplane anisotropic properties, to determine its exciton binding energy. We combine scanning tunneling spectroscopy and photoelectrochemical measurements with random phase approximation and Bethe-Salpeter equation calculations to obtain the electronic and optical bandgaps and thus the exciton binding energy. We find experimental values for the electronic bandgap, optical bandgap and exciton binding energy of 1.2 eV, 1.07 eV and 130 meV, respectively, and 1.15 eV, 1.05 eV and 100 meV for the corresponding theoretical results. The exciton binding energy is orders of magnitude larger than that of common semiconductors and comparable to bulk transition metal dichalcogenides, making TiS3 ribbons a highly interesting material for optoelectronic applications and for studying excitonic phenomena even at room temperature.

cond-mat.mes-hall↗

arXiv2015

Strain induced bang-gap engineering in layered $\text{TiS}_3$

By combining {\it ab initio} calculations and experiments we demonstrate how the band gap of the transition metal tri-chalcogenide TiS$_3$ can be modified by inducing tensile or compressive strain. We show by numerical calculations that the electronic band gap of layered TiS$_3$ can be modified for monolayer, bilayer and bulk material by inducing either hydrostatic pressure or strain. In addition, we find that the monolayer and bilayer exhibits a transition from a direct to indirect gap when the strain is increased in the direction of easy transport. The ability to control the band gap and its nature can have an impact in the use of TiS$_3$ for optical applications. We verify our prediction via optical absorption experiments that present a band gap increase of up to 10\% upon tensile stress application along the easy transport direction.

cond-mat.mtrl-sci↗

arXiv2015

Thermoelectric power of bulk black-phosphorus

The potential of bulk black-phosphorus for thermoelectric applications has been experimentally studied. The Seebeck Coefficient (S) has been measured in the temperature range from 300 K to 385 K, finding a value of S = +335 +- 10 uV/K at room temperature (indicating a naturally occurring p-type conductivity). S increases with temperature, as expected for p-type semiconductors, which can be attributed to an increase of the charge carrier density. The electrical resistance drops up to a 40 % while heating in the studied temperature range. As a consequence, the power factor at 385 K is 2.7 times higher than that at room temperature. This work demonstrates the feasibility of black-phosphorus in thermoelectric applications, such as thermal energy scavenging, which typically require devices with high performance at temperatures above room temperature.

cond-mat.mtrl-sci↗

arXiv2008

Diffraction of Coherent Light with Sinusoidal Amplitude by a Thin-Slit Grid

We report on the experimental findings of a thin-slit grid diffraction of a coherent light beam with sinusoidal amplitude. We create the sinusoidal amplitude by placing a thin-slit grid at the center of the dark fringes of an interference pattern resulting from laser light passing through a dual pinhole. The experimental results show good agreement with diffraction calculations of a thin-slit grid placed at the center of the dark fringes produced by two coherent beams that intersect at small angle. The results are applied to wire-grid diffraction in the Afshar experiment.

physics.optics↗

arXiv2007

Why Kastner analysis does not apply to a modified Afshar experiment

In an analysis of the Afshar experiment R.E. Kastner points out that the selection system used in this experiment randomly separates the photons that go to the detectors, and therefore no which-way information is obtained. In this paper we present a modified but equivalent version of the Afshar experiment that does not contain a selection device. The double-slit is replaced by two separate coherent laser beams that overlap under a small angle. At the intersection of the beams an interference pattern can be inferred in a non-perturbative manner, which confirms the existence of a superposition state. In the far field the beams separate without the use of a lens system. Momentum conservation warranties that which-way information is preserved. We also propose an alternative sequence of Stern-Gerlach devices that represents a close analogue to the Afshar experimental set up.

quant-ph↗

arXiv2007

Paradox in Wave-Particle Duality

We report on the simultaneous determination of complementary wave and particle aspects of light in a double-slit type "welcher-weg" experiment beyond the limitations set by Bohr's Principle of Complementarity. Applying classical logic, we verify the presence of sharp interference in the single photon regime, while reliably maintaining the information about the particular pinhole through which each individual photon had passed. This experiment poses interesting questions on the validity of Complementarity in cases where measurements techniques that avoid Heisenberg's uncertainty principle and quantum entanglement are employed. We further argue that the application of classical concepts of waves and particles as embodied in Complementarity leads to a logical inconsistency in the interpretation of this experiment.

quant-ph↗