arXiv subjects

Dominik Szczȩśniak

Publications and source records attributed to Dominik Szczȩśniak.

At least 19 recordsLinked to original sources

arXiv2026

Interplay of Kekulé order, flat bands and electron-phonon coupling in graphene

The Kekulé order in graphene is known to coexist with both an extended flat band near the van Hove singularity (VHS) and enhanced electron-phonon coupling. However, the microscopic origin of this interplay is still not fully understood. Here, this behavior is traced to the Kekulé-induced bond distortion and the resulting redistribution of electronic delocalization. In this picture, the conduction band below the VHS is observed to flatten with increasing Kekulé order, extending its intrinsically weakly dispersive region around the saddle point over a broader momentum range. In parallel, the VHS and dimensionless electron-phonon coupling exhibit approximately quadratic upward responses. The resulting enhancement of the electron-phonon coupling is found to be predominantly governed by the increasing density of states, with the effective deformation potential remaining weakly affected by the distortion. As such, the obtained results are consistent with previous theoretical and experimental studies, while also pointing toward the narrowing of the conduction band and a possible departure of the electron-phonon coupling from the conventional adiabatic regime. Altogether, they highlight the potential of controlled Kekulé ordering for engineering emergent correlated quantum phases in graphene.

cond-mat.mes-hall↗

arXiv2026

Nonlocal correlations for bosonic fields in black hole quantum atmosphere

Recent theoretical studies propose that Hawking radiation may not emerge strictly at the event horizon but rather from the spatially extended region surrounding a black hole, commonly referred to as the quantum atmosphere. In this work, we explore how this concept influences nonlocal quantum correlations in a bosonic bipartite system located at certain distance from a Schwarzschild black hole. By employing the measurement-induced nonlocality (MIN), as a quantifier of quantum correlations, we analyze the response of bosonic fields to the thermal and geometric characteristics associated with the Hartle-Hawking vacuum. In this manner, we extend previous studies that primarily focused on the fermionic systems. Our results reveal that, when quantum atmosphere is taken into account, the behavior of MIN departs from its conventional near-horizon profile. In particular, bosonic nonlocal correlations are found to exhibit a pronounced degradation at a finite radial distance from the event horizon and to ultimately vanish as scaled distance increases further. To some extent this behavior contrasts with the previously considered fermionic case, indicating that bosonic fields provide potentially stronger response to the quantum atmosphere.

quant-ph↗

arXiv2026

Entropic signatures of market response under concentrated policy communication

The first 100 days of Donald Trump second presidential term (January 20th - April 30th, 2025) featured policy actions with potential market repercussions, constituting a well-suited case study of a concentrated policy scenario. Here, we provide a first look at this period, rooted in the information theory, by analyzing major stock indices across the Americas, Europe as well as Asia and Oceania. Our approach jointly examines dispersion (standard deviation) and information complexity (entropy), but also employs a sliding window cumulative entropy to localize extreme events. We find a notable decoupling between the first two measures, indicating that entropy is not merely a proxy for amplitude but reflects the diversity of populated outcomes. As such, they allow us to capture both market volatility and narrative constraints, signaling large and coherent moves driven by policy changes. In turn, the cumulative entropy is found to notably increase during regional episodes with high information density, providing effective signatures of such events. We argue that the obtained results indicate short-term globally coupled, yet regionally modulated, market impacts with clear connection to introduced policies. In what follows, the presented entropic framework emerges as an efficient complement to standard methods for characterizing markets under turbulent conditions, with potential to enhance forecasting strategies such as the stochastic modeling.

q-fin.ST↗

arXiv2025

Quantum smell: tunneling mechanisms in olfaction

The mechanism by which odorants are recognized by olfactory receptors remains primarily unresolved. While charge transport is believed to play a significant role, its precise nature is still unclear. Here, we present a novel perspective by exploring the interplay between the intrinsic energy scales of odorant molecules and the gap states that facilitate intermolecular charge transport. We find that odorants act as weak tunneling conductors mainly because of the limited magnitude of electronic coupling. This behavior is further connected to electron-phonon interactions and reorganization energy, suggesting that physically meaningful values for these parameters emerge only in the deep off-resonant tunneling regime. These findings complement the swipe card model of olfaction, in which an odorant needs both the right shape to bind to a receptor and the correct vibrational frequency to trigger signal transduction. Moreover, they reveal that the underlying mechanisms are much more complex than previously assumed.

physics.chem-ph↗

arXiv2025

Electron-phonon coupling in Kekulé-ordered graphene

Breaking the intrinsic chirality of quasiparticles in graphene enables the emergence of new and intriguing phases. One such paradigmatic example is the bond density wave, which leads to a Kekulé-ordered structure and underpins exotic electronic states where electron-phonon interactions can play a fundamental role. Here, it is shown that the relevant physics of these correlations can be resolved locally, according to the behavior of interatomic characteristics. For this purpose a robust distance-dependent framework for describing electronic structure of graphene with Kekulé bond order is presented. Given this insight, the strength of electron-phonon interactions is found to scale linearly with the electronic coupling, contributing to a uniform picture of this relationship in distorted graphene structures. Moreover, it is shown that the introduced distortion yields a strongly non-uniform spatial distribution of the pairing strength that eventually leads to the induction of periodically distributed domains of enhanced electron-phonon coupling. These findings help elucidate certain peculiar aspects of phonon-mediated phenomena in graphene, particularly the associated superconducting phase, and offer potential pathways for their further engineering.

cond-mat.mes-hall↗

arXiv2025

Signatures of extreme events in the cumulative entropic spectrum

In this study, the cumulative effect of the empirical probability distribution of a random variable is identified as a factor that amplifies the occurrence of extreme events in datasets. To quantify this observation, a corresponding information measure is introduced, drawing upon Shannon entropy for joint probabilities. The proposed approach is validated using selected market data as case studies, encompassing various instances of extreme events. In particular, the results indicate that the introduced cumulative measure exhibits distinctive signatures of such events, even when the data is relatively noisy. These findings highlight the potential of the discussed concept for developing a new class of related indicators or classifiers.

physics.data-an↗

arXiv2025

Semiconducting and superconducting properties of 2D hexagonal materials

The beginning of high interest in two-dimensional (2D) crystals is marked by the synthesis of graphene, which constitutes exemplary monolayer material. This is due to the multiple extraordinary properties of graphene, particularly in the field of quantum electronic phenomena. However, there are electronic features that are notably missing in this material due to the inherent nature of its charge carriers. Of particular importance is that pristine graphene does not exhibit semiconducting or superconducting properties, preventing related applications. Certain modifications to graphene or even synthesis of sibling materials is needed to arrive with semiconducting and superconducting 2D hexagonal materials. Here, the representative examples of such materials are discussed in detail along with their expected properties. Special attention is given to the unique semiconducting and superconducting phenomena found in these materials e.g. the non-adiabatic superconductivity, spin- and valley-dependent conductivity or the bulk-like Schottky-type potential barriers. The discussion is supplemented with some pertinent conclusions and perspectives for future work.

cond-mat.mes-hall↗

arXiv2024

Dynamical reconstruction of the $Λ$CDM model in the scalar-tensor representation of $f\left(Q,T\right)$ gravity

Motivated by the growing interest in the nonmetricity-matter couplings, we develop the scalar-tensor formulation of recently introduced $f(Q,T)$ gravity, where $Q$ is the nonmetricity and $T$ is the trace of the energy-momentum tensor. The main properties of the scalar-tensor formalism for the Friedmann-Lema{\^ i}tre-Robertson-Walker (FLRW) Universe are discussed, and we introduce an appropriate set of dynamical variables to analyze the cosmic evolution of the scalar-tensor $f(Q,T)$ cosmology as a dynamical system. By considering two distinct cosmic fluids, namely matter and radiation, we have demonstrated that the cosmological phase space exhibits the typical curvature-dominated, radiation-dominated, matter-dominated, and exponentially accelerated fixed points. Furthermore, under an appropriate set of initial conditions compatible with the current observations from the Planck satellite, our analysis shows that the scalar-tensor $f(Q,T)$ successfully yields models indistinguishable from the $Λ$CDM cosmology and compatible with the weak-field solar system dynamics, without the inclusion of a cosmological constant $Λ$. Thus, the theory introduced herein may be regarded as a suitable candidate to describe the cosmological dynamics of the Universe.

gr-qc↗

arXiv2024

Entropy corrected geometric Brownian motion

The geometric Brownian motion (GBM) is widely employed for modeling stochastic processes, yet its solutions are characterized by the log-normal distribution. This comprises predictive capabilities of GBM mainly in terms of forecasting applications. Here, entropy corrections to GBM are proposed to go beyond log-normality restrictions and better account for intricacies of real systems. It is shown that GBM solutions can be effectively refined by arguing that entropy is reduced when deterministic content of considered data increases. Notable improvements over conventional GBM are observed for several cases of non-log-normal distributions, ranging from a dice roll experiment to real world data.

physics.data-an↗

arXiv2024

Dark matter effects of a black hole with nonsingular Yukawa-modified potential in Einstein-Gauss-Bonnet Gravity

This paper investigates the contribution of the nonsingular Yukawa-modified potential in the context of four-dimensional Einstein-Gauss-Bonnet (EGB) gravity modeling by a static and spherically symmetric black hole solution. These Yukawa-type corrections are essentially described along two parameters, $β$ and $λ$, affecting Newton's law of gravity at large distances, and a deformation parameter $\ell_0$, which is essential at short distances. Primarily, the strongest effect is encoded in $β$, which alters the total mass of the black hole with additional mass proportional to $β\mathcal{M}$, imitating the effects of dark matter at large distances from the black hole. In contrast, the effect due to $λ$ is small for astrophysical values. On the other hand, the EGB gravity is ruled by the Gauss-Bonnet (GB) coupling constant $α$, a fundamental parameter of the theory. We pay particular attention to thermodynamic stability, critical orbits, geodesics and quasinormal modes. The results demonstrate stability of the black hole solution for a range of values of the GB coupling constant $α$. Furthermore, this study investigates the null geodesic motion, namely the shadow behavior, providing intriguing results in relation to the size of the black hole shadow.

gr-qc↗

arXiv2023

Entropy of financial time series due to the shock of war

The concept of entropy is not uniquely relevant to the statistical mechanics but among others it can play pivotal role in the analysis of a time series, particularly the stock market data. In this area sudden events are especially interesting as they describe abrupt data changes which may have long-lasting effects. Here, we investigate the impact of such events on the entropy of financial time series. As a case study we assume data of polish stock market in the context of its main cumulative index. This index is discussed for the finite time periods before and after outbreak of the 2022 Russian invasion of Ukraine, acting as the sudden event. The analysis allows us to validate the entropy-based methodology in assessing market changes as driven by the extreme external factors. We show that qualitative features of market changes can be captured quantitatively in terms of the entropy. In addition to that, the magnitude of the impact is analysed over various time periods in terms of the introduced entropic index. To this end, the present work also attempts to answer whether or not the recent war can be considered as a reason or at least catalyst to the current economic crisis.

q-fin.ST↗

arXiv2023

Measurement-induced nonlocality for observers near a black hole

We present a systematic and complementary study of quantum correlations near a black hole by considering the measurement-induced nonlocality (MIN). The quantum measure of interest is discussed on the same footing for the fermionic, bosonic and mixed fermion-boson modes in relation to the Hawking radiation. The obtained results show that in the infinite Hawking temperature limit, the physically accessible correlations does not vanish only in the fermionic case. However, the higher frequency modes can sustain correlations for the finite Hawking temperature, with mixed system being more sensitive towards increase of the fermionic frequencies than the bosonic ones. Since the MIN for the latter modes quickly diminishes, the increased frequency may be a way to maintain nonlocal correlations for the scenarios at the finite Hawking temperature.

gr-qc↗

arXiv2023

Scalability of non-adiabatic effects in lithium-decorated graphene superconductor

The analysis is conducted to unveil how the non-adiabatic effects scale within the superconducting phase of lithium-decorated graphene (LiC$_{6}$). Based on the Eliashberg formalism it is shown that the non-adiabatic effects notably reduce essential superconducting parameters in LiC$_{6}$ and arise as a significant oppressor of the discussed phase. Moreover, nonadiabaticity is found to scale with the strength of superconductivity, proportionally to the phonon energy scale and inversely with respect to the electron-phonon coupling. These findings are partially in contrast to other theoretical studies and show that superconductivity in LiC$_{6}$ is more peculiar than previously anticipated. In this context, the guidelines for enhancing superconducting phase in LiC$_{6}$ and sibling materials are also proposed.

cond-mat.supr-con↗

arXiv2021

The phonon-mediated superconductivity in bismuthates by non-adiabatic pairing

In the present paper, the impact of small Fermi energy on the selected parameters of the superconducting state in Ba$_{1-x}$K$_{x}$BiO$_{3}$ (BKBO) is studied at $x \in (0.3, 0.4, 0.5)$. This is done by employing the adiabatic and non-adiabatic Eliashberg equations in context of the available experimental data. It is found that the retardation, strong-coupling and the non-adiabatic effects notably influence superconducting phase in BKBO. In particular, the electron-electron interaction, approximated here by the Coulomb pseudopotential, is argued to be reduced by the non-adiabatic effects that supplement retardation and allow for the phonon-mediated superconductivity. These findings are reinforced by further analysis of the isotope effect showing reduction of the isotope coefficient with respect to the canonical Bardeen-Cooper-Schrieffer (BCS) level, as caused by the interplay of all effects mentioned above. Although physics behind the isotope effect appears to be complex, its resulting behavior comply with the scenario for the conventional superconductors. In summary, obtained results confirm recent theoretical and experimental studies that suggest phonon-mediated mechanism of superconductivity in BKBO. However, they also point out that this phase cannot be properly described with the BCS theory due to the existence of somewhat unusual effects.

cond-mat.supr-con↗

arXiv2020

Magnetic flux noise in superconducting qubits and the gap states continuum

In the present study we investigate the selected local aspects of the metal-induced gap states (MIGSs) at the disordered metal-insulator interface, that were previously proposed to produce magnetic moments responsible for the magnetic flux noise in some of the superconducting qubit modalities. Our analysis attempts to supplement the available studies and provide new theoretical contribution toward their validation. In particular, we explicitly discuss the behavior of the MIGSs in the momentum space as a function of the local onsite energy deviation, that mimics random potential disorder at the interface. It is found, that when the difference between the characteristic electronic potentials in the insulator increases, the corresponding MIGSs become more localized. This effect is associated with the increasing degree of the potential disorder that was earlier observed to produce highly localized MIGSs in the superconducting qubits. At the same time, the presented findings show that the disorder-induced localization of the MIGSs can be related directly to the decay characteristics of these states as well as to the bulk electronic properties of the insulator. As a result, our study reinforces plausibility of the previous corresponding investigations on the origin of the flux noise, but also allows to draw future directions toward their better verification.

cond-mat.supr-con↗

arXiv2020

Gap states and valley-spin filtering in transition metal dichalcogenide monolayers

The magnetically-induced valley-spin filtering in transition metal dichalcogenide monolayers ($MX_{2}$, where $M$=Mo, W and $X$=S, Se, Te) promises new paradigm in information processing. However, the detailed understanding of this effect is still limited, regarding its underlying transport processes. Herein, it is suggested that the filtering mechanism can be greately elucidated by the concept of metal-induced gap states (MIGS), appearing in the electrode-terminated $MX_{2}$ materials {\it i.e.} the referential filter setup. In particular, the gap states are predicted here to mediate valley- and spin-resolved charge transport near the ideal electrode/$MX_{2}$ interface, and therefore to initiate filtering. It is also argued that the role of MIGS increases when the channel length is diminished, as they begin to govern the overall valley-spin transport in the tunneling regime. In what follows, the presented study yields fundamental scaling trends for the valley-spin selectivity with respect to the intrinsic physics of the filter materials. As a result, it facilitates insight into the analyzed effects and provide design guidelines toward efficient valley-spin filter devices, that base on the discussed materials or other hexagonal monolayers with a broken inversion symmetry.

cond-mat.mes-hall↗

arXiv2019

Signatures of non-adiabatic superconductivity in lithium-decorated graphene

Recent experimental studies confirmed that a long searched conventional superconducting phase in graphene can be induced via lithium deposition. However, the canonical character of the lithium-decorated graphene (LiC$_{6}$) superconductor postulated therein, as defined by the Bardeen-Cooper-Schrieffer (BCS) theory, is ambiguous due to the moderate electron-phonon coupling constant and low Fermi energy in this material. Herein, this issue is addressed within the Migdal-Eliashberg formalism and beyond it via the first-order electron-phonon vertex corrections, to account for the potentially pivotal effects, hitherto not captured. The conducted analysis yields similar value of the metal-superconductor transition temperature as in the previous studies ($T_{C} \sim 6$ K), yet for a weaker depairing electron correlations, which magnitude in the non-adiabatic regime approaches predictions of the Morel-Anderson model. Moreover, the characteristic ratio of the pairing gap and the inverse temperature is found to notably exceeds estimates of the BCS theory. In a results, it is argued that the superconducting state in LiC$_{6}$ may have non-canonical character strongly influenced by the non-adiabatic and retardation effects. Moreover, discussed phase appears as a vital case study, which suggests that other two-dimensional superconductors of hexagonal structure may exhibit similar non-canonical behavior as LiC$_{6}$.

cond-mat.supr-con↗

arXiv2018

Unbalanced superconductivity induced by the constant electron-phonon coupling on a square lattice

In the present paper, we analyze the properties of the unbalanced superconducting state on a square lattice with the constant value of the electron-phonon coupling function. We conduct our analysis in the framework of the Eliashberg formalism, explicitly considering {\bf k}-dependence of the electron and phonon dispersion relations. It is found that the balanced superconducting state does not induce itself in the system due to the high value of the electron effective mass. However, in the unbalanced case the thermodynamic properties of the superconducting condensate can be distinctly different from the predictions of the Bardeen-Cooper-Schieffer theory; when the coupling constant value in the diagonal channel of the self-energy is diminished comparing to the non-diagonal channel. This is due to the reduced dimensionality of the tested system and the strong-coupling effects included in the Eliashberg formalism.

cond-mat.supr-con↗