arXiv subjects

Vadim Cheianov

Publications and source records attributed to Vadim Cheianov.

At least 19 recordsLinked to original sources

arXiv2026

The effect of Coulomb interactions on relic neutrino detection via beta decaying impurities in (semi)metals

Measuring the electron neutrino mass is a long-standing objective and requires a high energy resolution of certain $β$-decay experiments, as well as a visible cosmic neutrino background (C$ν$B) spectrum. Many quantum mechanical and chemical effects could potentially impair the required resolution/visibility, e.g., the Coulomb interactions between the electrons in the $β$-decaying impurity and in the solid-state environment. We analyze the effect when hybridization is suppressed completely using a dielectric spacer, and also when hybridization is present up to the lowest nontrivial order in perturbation theory.

hep-ph↗

arXiv2025

Gumbel statistics for entanglement spectra of many-body localized eigenstates

An entanglement spectrum encodes statistics beyond the entanglement entropy, of which several have been studied in the context of many-body localization. We numerically study the extreme value statistics of entanglement spectra of many-body localized eigenstates. The physical information encoded in these spectra is almost fully carried by the few smallest elements, suggesting the extreme value statistics to have physical significance. We report the surprising observation of Gumbel statistics. Our result provides an analytical, parameter-free characterization of many-body localized eigenstates.

cond-mat.dis-nn↗

arXiv2025

Sensitivity of the spectral form factor to short-range level statistics

The spectral form factor is a dynamical probe for level statistics of quantum systems. The early-time behaviour is commonly interpreted as a characterization of two-point correlations at large separation. We argue that this interpretation can be too restrictive by indicating that the self-correlation imposes a constraint on the spectral form factor integrated over time. More generally, we indicate that each expansion coefficient of the two-point correlation function imposes a constraint on the properly weighted time-integrated spectral form factor. We discuss how these constraints can affect the interpretation of the spectral form factor as a probe for ergodicity. We propose a new probe, which eliminates the effect of the constraint imposed by the self-correlation. The use of this probe is demonstrated for a model of randomly incomplete spectra and a Floquet model supporting many-body localization.

cond-mat.dis-nn↗

arXiv2025

Quantum adiabaticity in many-body systems and almost-orthogonality in complementary subspace

We investigate why, in quantum many-body systems, the adiabatic fidelity and the overlap between the initial state and instantaneous ground states often yield nearly identical values. Our analysis suggests that this phenomenon results from an interplay between two intrinsic limits of many-body systems: the limit of small evolution parameters and the limit of large system sizes. In the former case, conventional perturbation theory provides a straightforward explanation. In the latter case, a key insight is that pairs of vectors in the Hilbert space orthogonal to the initial state tend to become nearly orthogonal as the system size increases. We illustrate these general findings with two representative models of driven many-body systems: the driven Rice-Mele model and the driven interacting Kitaev chain model.

quant-ph↗

arXiv2024

Importance of the X-ray edge singularity for the detection of relic neutrinos in the PTOLEMY project

Direct detection of relic neutrinos in a beta-decay experiment is an ambitious goal that has long been beyond the reach of available technology. One of the most challenging practical difficulties for such an experiment is managing a large amount of radioactive material without compromising the energy resolution required to distinguish useful events from the substantial beta-decay background. The PTOLEMY project offers an innovative solution to this problem by depositing radioactive material on graphene. While this approach is expected to address the main challenge, it introduces new issues due to the proximity of the beta decayers to a solid-state system. In this work, we focus on the effect of the shakeup of the graphene electron system caused by a beta-decay event. We calculate the distortion of the relic neutrino peaks resulting from this shakeup, analyze the impact of the distortion on the visibility of neutrino capture events, and discuss potential technological solutions to enhance the visibility of these events.

physics.ins-det↗

arXiv2023

Can we use heavy nuclei to detect relic neutrinos?

Recent analysis of the viability of solid state-based relic neutrino detectors has revealed the fundamental necessity for the use of heavy, $A>100$, $β$-decayers as neutrino targets. Of all heavy isotopes, $^{171}$Tm and $^{151}$Sm stand out for their sufficiently low decay energies, reasonable half-life times and stable daughter nuclei. However, the crucial bit of information, that is the soft neutrino capture cross-section is missing for both isotopes. The main reason for that is a particular type of $β$-decay, which precludes a simple link between the isotope's half-life time and the neutrino capture rate. Here we propose an experimental method to bypass this difficulty and obtain the capture cross-section of a soft neutrino by a given isotope from the isotope's $β$-spectrum.

hep-ph↗

arXiv2022

Bounds on quantum adiabaticity in driven many-body systems from generalized orthogonality catastrophe and quantum speed limit

We provide two inequalities for estimating adiabatic fidelity in terms of two other more handily calculated quantities, i.e., generalized orthogonality catastrophe and quantum speed limit. As a result of considering a two-dimensional subspace spanned by the initial ground state and its orthogonal complement, our method leads to stronger bounds on adiabatic fidelity than those previously obtained. One of the two inequalities is nearly sharp when the system size is large, as illustrated using a driven Rice-Mele model, which represents a broad class of quantum many-body systems whose overlap of different instantaneous ground states exhibits orthogonality catastrophe.

quant-ph↗

arXiv2022

Time scale for adiabaticity breakdown in driven many-body systems and orthogonality catastrophe

The adiabatic theorem is a fundamental result established in the early days of quantum mechanics, which states that a system can be kept arbitrarily close to the instantaneous ground state of its Hamiltonian if the latter varies in time slowly enough. The theorem has an impressive record of applications ranging from foundations of quantum field theory to computational recipes in molecular dynamics. In light of this success it is remarkable that a practicable quantitative understanding of what "slowly enough" means is limited to a modest set of systems mostly having a small Hilbert space. Here we show how this gap can be bridged for a broad natural class of physical systems, namely many-body systems where a small move in the parameter space induces an orthogonality catastrophe. In this class, the conditions for adiabaticity are derived from the scaling properties of the parameter dependent ground state without a reference to the excitation spectrum. This finding constitutes a major simplification of a complex problem, which otherwise requires solving non-autonomous time evolution in a large Hilbert space. We illustrate our general results by analyzing conditions for the transport quantization in a topological Thouless pump.

cond-mat.quant-gas↗

arXiv2021

Navigating the pitfalls of relic neutrino detection

Beta-spectrum of radioactive atoms was long ago predicted to bear an imprint of the Cosmic Neutrino Background (C$ν$B). Over the years, it has been recognised that the best chance of achieving the signal-to-noise ratio required for the observation of this effect lies with solid-state designs. Here we bring to the fore a fundamental quantum limitation on the type of beta-decayer that can be used in such a design. We derive a simple usability criterion and show that $^3\rm H$, which is the most popular choice, fails to meet it. We provide a list of potentially suitable isotopes and discuss why their use in C$ν$B detection requires further research.

hep-ph↗

arXiv2018

Random Matrix Ensemble for the Level Statistics of Many-Body Localization

We numerically study the level statistics of the Gaussian $β$ ensemble. These statistics generalize Wigner-Dyson level statistics from the discrete set of Dyson indices $β= 1,2,4$ to the continuous range $0 < β< \infty$. The Gaussian $β$ ensemble covers Poissonian level statistics for $β\to 0$, and provides a smooth interpolation between Poissonian and Wigner-Dyson level statistics. We establish the physical relevance of the level statistics of the Gaussian $β$ ensemble by showing near-perfect agreement with the level statistics of a paradigmatic model in studies on many-body localization over the entire crossover range from the thermal to the many-body localized phase. In addition, we show similar agreement for a related Hamiltonian with broken time-reversal symmetry.

cond-mat.dis-nn↗

arXiv2018

Necessary and sufficient condition for quantum adiabaticity in a driven one-dimensional impurity-fluid system

We study under what conditions the quantum adiabaticity is maintained in a closed many-body system consisting of a one-dimensional fluid and an impurity particle dragged through the latter by an external force. We employ an effective theory describing the low-energy sector of the system to derive the time dependence of the adiabaticity figure of merit -- the adiabatic fidelity. We find that in order to maintain adiabaticity in a large system the external force, $F_N$, should vanish with the system size, $N$, as $1/N$ or faster. This improves the necessary adiabatic condition $F_N=O(1/\log N)$ obtained for this system earlier [AIP Conf. Proc. 1936, 020024 (2018)]. Experimental implications of this result and its relation to the quasi-Bloch oscillations of the impurity are discussed.

cond-mat.quant-gas↗

arXiv2018

Many-body localization in the Fock space of natural orbitals

We study the eigenstates of a paradigmatic model of many-body localization in the Fock basis constructed out of the natural orbitals. By numerically studying the participation ratio, we identify a sharp crossover between different phases at a disorder strength close to the disorder strength at which subdiffusive behaviour sets in, significantly below the many-body localization transition. We repeat the analysis in the conventionally used computational basis, and show that many-body localized eigenstates are much stronger localized in the Fock basis constructed out of the natural orbitals than in the computational basis.

cond-mat.dis-nn↗

arXiv2018

Soft self-assembly of Weyl materials for light and sound

Soft materials can self-assemble into highly structured phases which replicate at the mesoscopic scale the symmetry of atomic crystals. As such, they offer an unparalleled platform to design mesostructured materials for light and sound. Here, we present a bottom-up approach based on self-assembly to engineer three-dimensional photonic and phononic crystals with topologically protected Weyl points. In addition to angular and frequency selectivity of their bulk optical response, Weyl materials are endowed with topological surface states, which allows for the existence of one-way channels even in the presence of time-reversal invariance. Using a combination of group-theoretical methods and numerical simulations, we identify the general symmetry constraints that a self-assembled structure has to satisfy in order to host Weyl points, and describe how to achieve such constraints using a symmetry-driven pipeline for self-assembled material design and discovery. We illustrate our general approach using block copolymer self-assembly as a model system.

cond-mat.soft↗

arXiv2018

Non-universality of the adiabatic chiral magnetic effect in a clean Weyl semimetal slab

The adiabatic chiral magnetic effect (CME) is a phenomenon by which a slowly oscillating magnetic field applied to a conducting medium induces an electric current in the instantaneous direction of the field. Here we theoretically investigate the effect in a ballistic Weyl semimetal sample having the geometry of a slab. We discuss why in a general situation the bulk and the boundary contributions towards the CME are comparable. We show, however, that under certain conditions the adiabatic CME is dominated by the Fermi arc states at the boundary. We find that despite the topologically protected nature of the Fermi arcs, their contribution to the CME is neither related to any topological invariant nor can generally be calculated within the bulk low-energy effective theory framework. For certain types of boundary, however, the Fermi arcs contribution to the CME can be found from the effective low energy Weyl Hamiltonian and the scattering phase characterising the collision of a Weyl excitation with the boundary.

cond-mat.mes-hall↗

arXiv2017

Adiabatic Chiral Magnetic Effect in Weyl semimetal wires

The Chiral Magnetic Effect (CME) is a phenomenon by which an electric current develops in the direction of a magnetic field applied to a material. Recent theoretical research suggests that the CME can be observed in thermal equilibrium provided that the magnetic field oscillates with finite frequency $ω$. Moreover, under certain conditions the amplitude of the electric current does not vanish in the adiabatic $ω\to 0$ limit, which we call here the adiabatic CME. In this work, we consider an adiabatic CME in a bounded sample. We demonstrate that the presence of the boundary significantly changes the nature of the effect. Using linear response theory, we derive a simple formula (conjectured earlier in arXiv:1512.02144) that enables us to describe the CME in a bounded setting based on the knowledge of the energy levels alone. We use this formula to investigate a particularly interesting example of the CME completely defined by the boundary effects.

cond-mat.mes-hall↗

arXiv2017

Quantum Many-Body Adiabaticity, Topological Thouless Pump and Driven Impurity in a One-Dimensional Quantum Fluid

When it comes to applying the adiabatic theorem in practice, the key question to be answered is how slow "slowly enough" is. This question can be an intricate one, especially for many-body systems, where the limits of slow driving and large system size may not commute. Recently we have shown how the quantum adiabaticity in many-body systems is related to the generalized orthogonality catastrophe [Phys. Rev. Lett. 119, 200401 (2017)]. We have proven a rigorous inequality relating these two phenomena and applied it to establish conditions for the quantized transport in the topological Thouless pump. In the present contribution we (i) review these developments and (ii) apply the inequality to establish the conditions for adiabaticity in a one-dimensional system consisting of a quantum fluid and an impurity particle pulled through the fluid by an external force. The latter analysis is vital for the correct quantitative description of the phenomenon of quasi Bloch oscillations in a one-dimensional translation invariant impurity-fluid system.

cond-mat.quant-gas↗

arXiv2017

The enigma of the $ν=2+\frac{3}{8}$ fractional quantum Hall effect

The fractional quantum Hall effect at $ν=2+3/8$, which has been definitively observed, is one of the last fractions for which no viable explanation has so far been demonstrated. Our detailed study suggests that it belongs to a new class of of exotic states described by the Bonderson-Slingerland wave function. Its excitations are non-Abelian anyons similar to those of the well studied Pfaffian state at 5/2, but its wave function has a more complex structure. Using the effective edge theory, we make predictions for various measurable quantities that should enable a confirmation of the underlying topological order of this state.

cond-mat.mes-hall↗

arXiv2015

Fractional quantum Hall effect in bilayer graphene beyond the single Landau level approximation

Bilayer graphene has been predicted to give unprecedented tunability of the electron-electron interaction with the help of external parameters, allowing one to stabilize different fractional quantum Hall states. Recent experimental works make theoretical analysis of such systems extremely relevant. In this paper we describe a methodology for investigating the possibility of realizing specific fractional quantum Hall states in bilayer graphene taking into account polarization effects and virtual interband transitions. We apply this methodology to explore the possibility of realizing the Moore-Read Pfaffian state in bilayer graphene.

cond-mat.str-el↗