arXiv subjects

Marlo Kunzner

Publications and source records attributed to Marlo Kunzner.

6 recordsLinked to original sources

arXiv2026

Time-state superposition in non-equilibrium fluidized granular matter

Despite being intrinsically athermal and strongly driven, granular materials can exhibit remarkably glass-like dynamics. Whether their rheology can be described by the same scaling concepts remains an open question. Here, we investigate the linear viscoelastic response of an air-fluidized granular bed using small-amplitude oscillatory shear over a broad range of fluidization states. We show that the frequency-dependent spectra collapse onto a single master curve when shifted by a state-dependent relaxation time, establishing a time-state superposition principle analogous to time-temperature superposition in molecular glasses. The master curve spans more than five decades in relaxation time and is quantitatively described by a Cole-Davidson relaxation spectrum. By comparison with continuous shear measurements, we identify tribocharging as the origin of history-dependent deviations from universal scaling. Our results demonstrate that fluidization primarily rescales a single structural relaxation time while preserving the underlying relaxation spectrum, establishing a direct connection between the rheology of driven granular matter and molecular glass-forming liquids.

cond-mat.soft↗

arXiv2025

Towards probing velocity distributions in dense granular matter: Utilizing Fiber Bragg Gratings

Granular gases are commonly characterized through their velocity distribution, which provides access to the granular temperature. In experiments, velocity distributions are typically obtained by particle tracking, which however becomes limited at moderate and high particle densities. As a way forward, we propose a new technique for measuring particle velocities in situ by using a Fiber Bragg Grating (FBG) sensor, which remains applicable at significantly higher particle densities.The FBG sensor detects strain pulses induced by particle-fiber collisions, from which the velocity of the impacting particle can be derived. Applying this method to an ensemble of granular particles allows to extract its velocity distributions as we present for a granular system excited by a vibrational shaker. We validate the extracted velocity distribution against conventional particle-tracking measurements, confirming the reliability of the FBG-based technique.

cond-mat.dis-nn↗

arXiv2025

Demonstration of domain wall current in MgO-doped lithium niobate single crystals up to 400 °C

Conductive ferroelectric domain walls (DWs) represent a promising topical system for the development of nanoelectronic components and device sensors to be operational at elevated temperatures. DWs show very different properties as compared to their hosting bulk crystal, in particular with respect to the high local electrical conductivity. The objective of this work is to demonstrate DW conductivity up to temperatures as high as \SI{400}{\degreeCelsius} which extends previous studies significantly. Experimental investigation of the DW conductivity of charged, inclined DWs is performed using \SI{5}{\mole\percent} MgO-doped lithium niobate single crystals. \CR{Current-voltage (\IV) curves are determined by DC electrometer measurements and impedance spectroscopy and found to be identical. Moreover, impedance spectroscopy enables to recognize artifacts such as damaged electrodes. Temperature dependent measurements} over repeated heating cycles reveal two distinct thermal activation energies for a given DW, with the higher of the activation energies only measured at higher temperatures. Depending on the specific sample, the higher activation energy is found above \SI{160}{\degreeCelsius}~to~\SI{230}{\degreeCelsius}. This suggests, in turn, that more than one type of defect/polaron is involved, and that the dominant transport mechanism changes with increasing temperature. First principles atomistic modelling suggests that the conductivity of inclined domain walls cannot be solely explained by the formation of a 2D carrier gas and must be supported by hopping processes. This holds true even at temperatures as high as \SI{400}{\degreeCelsius}. Our investigations underline the potential to extend \DWC based nanoelectronic and sensor applications even into the so-far unexplored temperature range up to \SI{400}{\degreeCelsius}.

physics.app-ph↗

arXiv2025

Observing the Glass and Jamming Transitions of Dense Granular Material in Microgravity

The present study investigates a weakly pulsed granular system of polystyrene spheres under long-time microgravity conditions on the International Space Station (ISS). The spheres are measured using Diffusing Wave Spectroscopy (DWS) and are described by mean square displacements (MSDs). Our aim is to use this technique to show the first experimental evidence of glassy dynamics in dense granular media in microgravity and subsequently compare these results with ground-based measurements to see how the nature of these dynamics change without the influence of gravity. Our results show that as we densify the sample in microgravity, glassy dynamics appear at a volume fraction 1.6\% lower than on ground. We also show how the influence of gravity can affect how dense a granular system one can prepare by comparing the final jamming point of our sample on the ISS compared to our ground setup. We show that jamming occurs at a volume fraction 0.5\% lower in space compared to on ground. Showing that we can create denser states when a granular system is in the presence of a stronger gravitational field.

cond-mat.soft↗

arXiv2025

The Dynamics in Vibro-fluidized Beds: A Diffusing Wave Spectroscopy Study

We demonstrate the densification of a granular model system of polystyrene spheres over time by shaking with varying excitation amplitudes or effective temperatures. This densification is quantified by the mean square displacement (MSD), which is measured by diffuse wave spectroscopy (DWS) of a sinusoidally excited vibrating fluidized granular bed. The DWS method also extracts the inherent heterogeneous dynamics of the system in the bulk and at the wall. Through an empirical model-based extraction we obtain the ballistic and diffusive time constants, as well as caging sizes, which were found to depend on temperature and density. The results obtained from this study reveal a sub-diffusive power-law behavior in the MSD, indicating an arrest of motion and potentially a glassy system, especially in cases where the excitation is low to moderate compared to gravity. The extracted MSD caging sizes are two orders smaller than the Lindeman length found in colloidal systems.

cond-mat.soft↗

arXiv2024

High-temperature domain wall current in Mg-doped lithium niobate single crystals up to 400°C

Conductive ferroelectric domain walls (DWs) represent a promising topical system for the development of nanoelectronic components and devices. DWs show very different properties as compared to their bulk counterparts. Of central interest here is the domain wall current (DWC) of charged DWs in 5mol\% Mg-doped lithium niobate single crystals; in contrast to former works, we extend the DWC study here to temperatures as high as 400$^\circ$C. Both the temporal stability and the thermal activation energies of 90 - 160 meV are readily deduced from current-voltage sweeps as recorded over multiple heating cycles. Our experimental work is backed up by atomistic modelling of the DWC. The latter suggests that a large band bending renders head-to-head and tail-to-tail DWs semimetallic. These detailed investigations underline the potential to extend DWC-based nanoelectronic applications even into the so-far unexplored high-temperature regime.

cond-mat.mtrl-sci↗