arXiv subjects

Camelia Prodan

Publications and source records attributed to Camelia Prodan.

At least 19 recordsLinked to original sources

arXiv2025

Acoustic Metamaterials with Positive and Negative Couplings: Modular and One Piece Architectures for Topological Models

We describe two 3D-printing approaches for realizing tight-binding models in acoustic metamaterials using H-shaped resonators: a modular system with tunable interconnections and an integrated one-piece design for reducing dissipation. The platform supports both positive and negative coupling through geometric control, enabling accurate acoustic analogs of topological models. By tuning the coupling length (CL), we eliminate detuning effects and preserve particle-hole symmetry. We further quantify the influence of the Total Coupling Area (TCA) on band topology and derive conditions for constant-area coupling. The system was tested on SSH and Kitaev chains, revealing midgap edge and interface states, confirming topological behavior in both configurations.

cond-mat.mes-hall↗

arXiv2025

Experimental Milestones Towards Majorana Braiding with Acoustic Metamaterials

Here we show the first experimental implementation of the fully general Kitaev chain with complex-valued order parameter $\Delta$ and site-varying synthetic chemical potential $\mu$, using a passive multilayer acoustic resonator design and fabrication. Our laboratory model faithfully reproduces the key symmetries and the topological phase diagram of the model, and displays robust Majorana-like edge modes spatially localized at smoothly engineered domain walls and energetically localized in the middle of the bulk spectral gap. We demonstrate precise control over mode positioning through smooth spatial variations of $\mu$, and validate the stability of the modes and of the spectral gap under continuous and complex variations of $\Delta$ -- both critical requirements for topological braiding operations. These results establish and validate the fundamental building blocks for experimental implementation of complete braiding protocols, opening concrete pathways toward accessible non-abelian physics and topologically protected information processing.

cond-mat.mes-hall↗

arXiv2023

Symmetry-Preserving Coupling Method for Topological Acoustic Metamaterials

In this paper we investigate different types of couplings used in acoustic metamaterials requiring preservation of symmetries. For testing we use the SSH model to test whether topologically edge and interface modes are supported with the different types of connection. We observed that a modular platform where the resonators are coupled through the bottom is the simplest method that is accurate and flexible.

physics.app-ph↗

arXiv2023

Isolating a Single Microtubule in Nanofluidic Device

Biological systems have been theoretically predicted to support phononic topological wave-modes, similar to the ones existing in meta-materials. The existing methods to measure these modes, however cannot be applied to biological systems; new techniques have to be developed to accommodate phononic measurements in life science. Motivated by this perspective, we report a nanofluidic device for studying one microtubule at a time. Microchannels etched into fused-silica using reactive ion etching were interfaced with nanochannels written and etched by electron beam lithography and reactive ion etching, and sealed with a PDMS-coated glass coverslip. The microchannels are 1 micron deep and 100 micron wide, and the nanochannels are 150 nm deep and 750 nm wide, they are tested to be effective for isolating microtubules. The methods presented here are for an adaptable nanofluidic platform for phonon measurements in biopolymers made of proteins or DNA.

physics.bio-ph↗

arXiv2022

Revealing Topology in Metals using Experimental Protocols Inspired by $K$-Theory

Topological metals are special conducting materials with gapless band structures and nontrivial edge-localized resonances, whose discovery has proved elusive because the traditional topological classification methods do not apply in this context. Inspired by recent theoretical developments that leveraged techniques from the field of $C^*$-algebras to identify topological metals \cite{cerjan_local_2021}, here, we directly observe topological phenomena in gapless acoustic crystals and provide a general experimental technique to demonstrate their topology. Specifically, we not only observe robust boundary-localized states in a topological acoustic metal, but also re-interpret a composite operator, mathematically derived from the K-theory of the problem, as a new Hamiltonian, whose physical implementation allows us to directly observe a topological spectral flow and measure the topological invariants. Our observations and experimental protocols may offer insights for discovering topological behavior across a wide array of artificial and natural materials that lack bulk band gaps.

cond-mat.mes-hall↗

arXiv2022

Topological D-Class Physics with Passive Acoustic Elements

In this work, we supply an engineering solution that paves the way to the implementation of the full classification table of topological insulators with passive acoustic crystals. As an example, we design an acoustic crystal displaying the full range of characteristics of a topological insulator from class D, such as non-trivial Chern numbers and an exact particle-hole symmetry for both bulk and edge dynamics. The key is a particular geometry of the acoustic resonators that facilitates a large number of independent and equal-strength couplings, eight to be precise, such that the mode-coupling theory remains accurate. The latter enables us to implement with high fidelity the de-complexified tight-binding model generating the topological phases from class D in 2-dimensions, previously announced in [Barlas et al, PRB (2018)]. The successful realization of a topological acoustic crystal from class D paves the way to the observation of the Majorana-like modes stabilized by pi-fluxes.

cond-mat.mes-hall↗

arXiv2022

Observation of Phase Controllable Majorana-like Bound States in Metamaterial-based Kitaev Chain Analogues

We experimentally demonstrate that Majorana-like bound states (MLBSs) can occur in quasi-one-dimensional metamaterials, analogous to Majorana zero modes (MZM) in the Kitaev chain. In a mechanical spinner ladder system, we observe a topological phase transition and spectral-gap-protected edge MLBSs. We characterize the decaying and oscillatory nature of these MLBS pairs and their phase-dependent hybridization. It is shown that the hybridization can be tuned to yield the analogue of parity switching in MZMs, a key element of topological qubits. We find strong agreements with theory.

cond-mat.mtrl-sci↗

arXiv2020

Revealing the boundary Weyl physics of the four-dimensional Hall effect via phason engineering in metamaterials

Quantum Hall physics has been theoretically predicted in 4-dimensions and higher. In hypothetical 2n-dimensions, the topological characters of both the bulk and the boundary are manifested as quantized non-linear transport coefficients that connect, respectively, to the n-th Chern number of the bulk gap projection and to the n-th winding number of the Weyl spectral singularities on the (2n-1)-dimensional boundaries. Here, we introduce the concept of phason engineering in metamaterials and use it as a vehicle to access and apply the quantum Hall physics in arbitrary dimensions. Using these specialized design principles, we fabricate a re-configurable 2-dimensional aperiodic acoustic crystal with a phason living on a 2-torus, giving us access to the 4-dimensional quantum Hall physics. Also, we supply a direct experimental confirmation that the topological boundary spectrum assembles in a Weyl singularity when mapped as function of the quasi-momenta. We also demonstrate topological wave steering enabled by the Weyl physics of the 3-dimensional boundaries.

cond-mat.mes-hall↗

arXiv2020

Experimental Demonstration of Dynamic Topological Pumping Across Incommensurate Bilayered Acoustic Metamaterials

A Thouless pump can be regarded as a dynamical version of the integer quantum Hall effect. In a finite-size configuration, such topological pump displays edge modes that emerge dynamically from one bulk-band and dive into the opposite bulk-band, an effect that can be reproduced with both quantum and classical systems. Here, we report the first un-assisted dynamic energy transfer across a metamaterial, via pumping of such topological edge modes. The system is a topological aperiodic acoustic crystal, with a phason that can be fast and periodically driven in adiabatic cycles. When one edge of the metamaterial is excited in a topological forbidden range of frequencies, a microphone placed at the other edge starts to pick up a signal as soon as the pumping process is set in motion. In contrast, the microphone picks no signal when the forbidden range of frequencies is non-topological.

cond-mat.mes-hall↗

arXiv2020

Observation of Flat Frequency Bands at Open Edges and Antiphase Boundary Seams in Topological Mechanical Metamaterials

Motivated by the recent theoretical studies on a two-dimensional (2D) chiral Hamiltonian based on the Su-Schrieffer-Heeger chains, we experimentally and computationally demonstrate that topological flat frequency bands can occur at open edges of 2D planar metamaterials and at antiphase boundary seams of ring-shaped or tubular metamaterials. Specifically, using mechanical systems made of magnetically coupled spinners, we reveal that the presence of the edge or seam bands that are flat in the entire projected reciprocal space follows the predictions based on topological winding numbers. The edge-to-edge distance sensitively controls the flatness of the edge bands and the localization of excitations. The analogue of the fractional charge state is also observed. Possible realizations of flat bands in a large class of metamaterials, including photonic crystals and electronic metamaterials, are discussed.

cond-mat.mes-hall↗

arXiv2018

Observation of topological edge modes in a quasi-periodic acoustic waveguide

Topological boundary and interface modes are generated in an acoustic waveguide by simple quasi-periodic patternings of the walls. The procedure opens many topological gaps in the resonant spectrum and qualitative as well as quantitative assessments of their topological character are supplied. In particular, computations of the bulk invariant for the continuum wave equation are performed. The experimental measurements reproduce the theoretical predictions with high fidelity. In particular, acoustic modes with high Q-factors localized in the middle of a breathable waveguide are engineered by a simple patterning of the walls.

cond-mat.mes-hall↗

arXiv2018

Theory and Experimental Investigation of the Quantum Valley Hall Effect

The quantum valley Hall effect (QVHE) has been observed in a variety of experimental setups, both quantum and classical. While extremely promising for applications, one should be reminded that QVHE is not an exact topological phenomenon and that, so far, it has been fully understood only qualitatively in certain extreme limits. Here we present a technique to relate QVHE systems with exact quantum spin-Hall insulators that accept real-space representations, without taking any extreme limit. Since the bulk-boundary correspondence is well understood for the latter, we are able to formulate precise quantitative statements about the QVHE regime and its robustness against disorder. We further investigate the effect using a novel experimental platform based on magnetically coupled spinners. Visual renderings, quantitative data and various tests of the domain-wall modes are supplied, hence giving an unprecedented insight into the effect.

cond-mat.mes-hall↗

arXiv2018

Topological Edge Modes by Smart Patterning

The research in topological materials and meta-materials reached maturity and is now gradually entering the phase of practical applications and devices. However, scaling down the experimental demonstrations definitely presents a challenge. In this work, we study coupled identical resonators whose collective dynamics is fully determined by the pattern in which the resonators are arranged. We call a pattern topological if boundary resonant modes fully fill all existing spectral gaps whenever the pattern is halved. This is a characteristic of the pattern and is entirely independent of the structure of the resonators and the details of the couplings. Existence of such patterns is proven using $K$-theory and exemplified using a novel experimental platform based on magnetically coupled spinners. Topological meta-materials built on these principles can be easily engineered at any scale, providing a practical platform for applications and devices.

physics.app-ph↗

arXiv2017

Dynamical Majorana Edge Modes in a Broad Class of Topological Mechanical Systems

Mechanical systems can display topological characteristics similar to that of topological insulators. Here we report a large class of topological mechanical systems related to the BDI symmetry class. These are self-assembled chains of rigid bodies with an inversion center and no reflection planes. The particle-hole symmetry characteristic to the BDI symmetry class stems from the distinct behavior of the translational and rotational degrees of freedom under inversion. This and other generic properties led us to the remarkable conclusion that, by adjusting the gyration radius of the bodies, one can always simultaneously open a gap in the phonon spectrum, lock-in all the characteristic symmetries and generate a non-trivial topological invariant. The particle-hole symmetry occurs around a finite frequency, hence we can witness a dynamical topological Majorana edge mode. Contrasting a floppy mode occurring at zero frequency, a dynamical edge mode can absorb and store mechanical energy, potentially opening new applications of topological mechanics.

cond-mat.soft↗

arXiv2009

Topological phonon modes and their role in dynamic instability of microtubules

Microtubules (MTs) are self-assembled hollow protein tubes playing important functions in live cells. Their building block is a protein called tubulin, which self-assembles in a particulate 2 dimensional lattice. We study the vibrational modes of this lattice and find Dirac points in the phonon spectrum. We discuss a splitting of the Dirac points that leads to phonon bands with nonzero Chern numbers, signaling the existence of topological vibrational modes localized at MTs edges, which we indeed observe after explicit calculations. Since these modes are robust against the large changes occurring at the edges during the dynamic cycle of the MTs, we can build a simple mechanical model to illustrate how they would participate in this phenomenon.

cond-mat.soft↗

arXiv2008

Probing the membrane potential of living cells by dielectric spectroscopy

In this paper we demonstrate a quantitative way to measure the membrane potential of live cells by dielectric spectroscopy. We also show that the values of the membrane potential obtained using our technique are in good agreement with those obtained using traditional methods-voltage sensitive dyes. The membrane potential is determined by fitting the experimental dielectric dispersion curves with the dispersion curves obtain from a theoretical model. Variations in the membrane potential were induced by modifying the concentration of potassium chloride in the solution of the cell suspension in the presence of valinomycin. For exemplification of the method, E. coli were chosen for our experiments.

cond-mat.soft↗

arXiv2008

Correcting the polarization effect in low frequency Dielectric Spectroscopy

We demonstrate a simple and robust methodology for measuring and analyzing the polarization impedance appearing at interface between electrodes and ionic solutions, in the frequency range from 1 to $10^6$ Hz. The method assumes no particular behavior of the electrode polarization impedance and it only makes use of the fact that the polarization effect dies out with frequency. The method allows a direct and un-biased measurement of the polarization impedance, whose behavior with the applied voltages and ionic concentration is methodically investigated. Furthermore, based on the previous findings, we propose a protocol for correcting the polarization effect in low frequency Dielectric Spectroscopy measurements of colloids. This could potentially lead to the quantitative resolution of the $α$-dispersion regime of live cells in suspension.

cond-mat.soft↗

arXiv2008

The removal of the polarization errors in low frequency dielectric spectroscopy

Electrode polarization error is the biggest problem when measuring the low frequency dielectric properties of electrolytes or suspensions of particles, including cells, in electrolytes. We present a simple and robust method to remove the polarization error, which we demonstrate to work on weak and strong ionic electrolytes as well as on cell suspensions. The method assumes no particular behavior of the electrode polarization impedance; it makes use of the fact that the effect dies out with frequency. The method allows for direct measurement of the polarization impedance, whose behavior with the applied voltages, electrode distance and ionic concentration is investigated.

cond-mat.soft↗