Electrical conduction and relaxation phenomena in bismuth borate glasses in the composition 2Bi2O3-B2O3 (Bi4B2O9) were investigated. Dielectric studies carried out on these glasses revealed near constant loss (NCL) response in the 1 kHz to 1MHz frequency range at moderately high temperatures (300-450K) associated with relatively low loss (D=0.006) and high dielectric constant (εr'=37) at 1kHz,300K. The variation in AC conductivity with temperature at different frequencies showed a cross over from NCL response characterized by local ion vibration within the potential well to universal Joncher's power law dependence triggered by ion hopping between potential wells or cages. Thermal activation energy for single potential well was found to be 0.48 \pm 0.05eV from cross over points. Ionic conduction and relaxation processes were rationalized by modulus formalism. The promising dielectric properties (relatively high εr' and low D) of the present glasses were attributed to high density (93 % of its crystalline counterpart), high polarizability and low mobility associated with heavy metal cations, Bi3+.
Amorphous silicon contains tunneling two-level systems, which are the dominant energy loss mechanisms for amorphous solids at low temperatures. These two-level systems affect both mechanical and electromagnetic oscillators and are believed to produce thermal and electromagnetic noise and energy loss. However, it is unclear whether the two-level systems that dominate mechanical and dielectric losses are the same; the former relies on phonon-TLS coupling, with an elastic field coupling constant, $γ$, while the latter depends on a TLS dipole moment, $p_0$, which couples to the electromagnetic fie…
Evidence for anisotropic dielectric properties of monoclinic hafnia using high-resolution TEM valence electron energy-loss spectroscopy and ab initio time-dependent density-functional theory
Low frequency dielectric measurements on plexiglass (PMMA) show that cooling and heating the sample at constant rate give an hysteretic dependence on temperature of the dielectric constant $ε$. A temporary stop of cooling produces a downward relaxation of $ε$. Two main features are observed i) when cooling is resumed $ε$ goes back to the values obtained without the cooling stop (i.e. the low temperature state is independent of the cooling history) ii) upon reheating $ε$ keeps the memory of the aging history ({\it Memory}). The analogies and differences with similar experiments done in spin gla…
Low-loss deposited dielectrics will benefit superconducting devices such as integrated superconducting spectrometers, superconducting qubits and kinetic inductance parametric amplifiers. Compared with planar structures, multi-layer structures such as microstrips are more compact and eliminate radiation loss at high frequencies. Multi-layer structures are most easily fabricated with deposited dielectrics, which typically exhibit higher dielectric loss than crystalline dielectrics. We measured the sub-kelvin and low-power microwave and mm-submm wave dielectric loss of hydrogenated amorphous sili…
Quantum two-level systems (TLSs) intrinsic to glasses induce decoherence in many modern quantum devices, such as superconducting qubits. Although the low-temperature physics of these TLSs is usually well-explained by a phenomenological standard tunneling model of independent TLSs, the nature of these TLSs, as well as their behavior out of equilibrium and at high energies above 1 K, remain inconclusive. Here we measure the non-equilibrium dielectric loss of TLSs in amorphous silicon using a superconducting resonator, where energies of TLSs are varied in time using a swept electric field. Our re…
Complex Permittivity Measurements at Variable Temperatures of Low Loss Dielectric Substrates Employing Split Post and Single Post Dielectric Resonators
Our study shows that deposited Ge and Si dielectric thin-films can exhibit low microwave losses at near single-photon powers and sub-Kelvin temperatures ($\approx$40 mK). This low loss enables their use in a wide range of devices, including low-loss coplanar, microstrip, and stripline resonators, as well as layers for device isolation, inter-wiring dielectrics, and passivation in microwave and Josephson junction circuit fabrication. We use coplanar microwave resonator structures with narrow trace widths of 2-16 $μ\textrm{m}$ to maximize the sensitivity of loss tangent measurements to the inter…
The electronic properties of two-dimensional (2D) materials depend sensitively on the underlying atomic arrangement down to the monolayer level. Here we present a novel strategy for the determination of the band gap and complex dielectric function in 2D materials achieving a spatial resolution down to a few nanometers. This approach is based on machine learning techniques developed in particle physics and makes possible the automated processing and interpretation of spectral images from electron energy-loss spectroscopy (EELS). Individual spectra are classified as a function of the thickness w…
Dielectrics with low loss at microwave frequencies are imperative for high-coherence solid-state quantum computing platforms. We study the dielectric loss of hexagonal boron nitride (hBN) thin films in the microwave regime by measuring the quality factor of parallel-plate capacitors (PPCs) made of NbSe$_{2}$-hBN-NbSe$_{2}$ heterostructures integrated into superconducting circuits. The extracted microwave loss tangent of hBN is bounded to be at most in the mid-10$^{-6}$ range in the low temperature, single-photon regime. We integrate hBN PPCs with aluminum Josephson junctions to realize transmo…
The complex dielectric constant $\hatε = ε_1 + i ε_2$ of SrTiO$_3$ reaches high values $ε_1 \approx 2*10^{4}$ at cryogenic temperatures, while the dielectric losses ($ε_2$) are much stronger than for other crystalline dielectrics. SrTiO$_3$ is a common substrate for oxide thin films, like the superconducting LaAlO$_3$/SrTiO$_3$ system, but the large $ε_1$ and $ε_2$ restrict high-frequency quantum devices on SrTiO$_3$. Here we present superconducting coplanar Nb resonators on SrTiO$_3$, which we successfully operate in a distant-flip-chip geometry at frequencies that exceed 1 GHz. We find a pro…
Non-equilibrium molecular dynamics simulations are performed to investigate the dynamic behavior of three-dimensional binary glasses prepared via an instantaneous quench across the glass transition. We found that with increasing strain amplitude up to a critical value, the potential energy approaches lower minima in steady state, whereas the amplitude of shear stress oscillations becomes larger. Below the yielding transition, the storage modulus dominates the mechanical response, and the gradual decay of the potential energy over consecutive cycles is accompanied by reduction in size of transi…
