Abstract Formulated a hundred years ago, the Bridgman formula for thermal conductivity of liquids postulates a proportionality between sound velocity and thermal conductivity and therefore appoints phonons as the main carriers of heat in a liquid. Its empirical success has been under-appreciated and its conceptual implications beyond the case of classical liquids has been overlooked. We review its origin, its links to hydrodynamic Euler equations and the fundamental paradox surrounding the parabolic heat equation and its fate across the quantum-classical crossover.
Abstract In one-dimensional class-D superconductors, the relative signs of the Bogoliubov--de Gennes (BdG) masses at particle--hole-invariant momenta fix the bulk $\mathbb Z_2$ invariant. Band energies and transition-frequency peak locations alone cannot determine these signs. We reconstruct each signed endpoint mass from the equal-time responses of two fixed transverse preparations to a calibrated probe. Within this two-preparation class with equal independent Gaussian slope noise, orthogonal axes maximize the worst-case Fisher information over the probe orientation and attain the Cram'er--Rao bound. The endpoint product gives the class-D invariant but only the parity of a general BDI winding number. In the four-band Rashba model, a full-matrix identity gives positive finite-packet attenuation for sinusoidal spin--orbit coupling and a wrapped-Gaussian momentum distribution. A conditional reference-dot construction maps the two-level algebra to charge readout. Full finite-ring calculations quantify single-pulse charge deviations and verify that preparation-phase cycling is equivalent to analysis-phase cycling for a normal reference dot. The results establish a symmetry-constrained reconstruction and its scope, not a sensitivity advantage over phase-sensitive Ramsey readout or a direct electric-current measurement.
Abstract In this work, we use first-principles calculations to investigate the incorporation and diffusion of carbon, hydrogen, oxygen, nitrogen, sulfur, and boron in $\alpha$-Ti, while also revisiting the case of vacancies. Calculations show that, when occupying interstitial sites, all species prefer to reside in octahedral positions. However, boron and sulfur seem to prefer substitution sites to interstitial sites. With regard to diffusivity, we analyze in detail the migration mechanisms for C, H, O and N, and compare the diffusion coefficients obtained with experimental data. For B, S and vacancies, the diffusion coefficients are evaluated within the framework of the eight-frequency model. The influence of stress on the solubility and diffusivity of interstitial species is finally investigated using elastic and elastodiffusion theories. It is found that the effect is weak.
Abstract Graphene transport experiments probe relaxation through different observables, timescales and measurement domains, making direct comparison of reported relaxation parameters difficult. Here we develop a kernel-first, provenance-constrained methodology for determining what aspects of relaxation structure can be identified from heterogeneous transport measurements before assigning them a common physical interpretation. The approach distinguishes measured, processed, fitted and theoretically derived quantities, and separates response magnitude, kernel sensitivity and experimentally observed state evolution. The method is applied to three complementary graphene experiments. Frequency-resolved complex conductivity provides identifiable spectral relaxation descriptors and, where an admissible parametrisation is supported, permits explicit kernel-sensitivity and state-trajectory analysis. Ultrafast electronic heat spreading constrains an additional short-time response relative to an independently determined momentum-relaxation interval, but does not identify a unique kernel time. DC electrical and thermal measurements constrain integrated response weights, geometry dependence and a relative relaxation hierarchy without uniquely determining temporal kernel shape. The three experiments therefore occupy different levels of dynamical identifiability rather than providing interchangeable relaxation times. A localized change in an effective-kernel trajectory is not by itself interpreted as a triggered process. The stronger test requires such a change to reproducibly predict an independently measured dynamical response. We propose a same–device, cross-domain experiment implementing this criterion across controlled state trajectories. The principal contribution is a general analysis methodology for determining what relaxation information heterogeneous measurements support and what additional evidence is required before state-dependent response is promoted to a physical mechanism.
Abstract Two-dimensional Janus monolayers with intrinsic magnetism have drawn increasing attention due to their broken out-of-plane symmetry and unique multifunctional properties. This review surveys recent progress on magnetic Janus monolayers, with an emphasis on the theoretical advances that currently dominate the field while also critically assessing the available experimental foundation. The review begins by introducing the crystal and electronic structures of representative systems, followed by a discussion of magnetic exchange, magnetic anisotropy energy, and strain engineering. Several emergent phenomena arising from the Janus architecture, including piezoelectricity, the quantum anomalous Hall effect, and valley polarization, are then presented. In addition, established synthesis routes for non-magnetic Janus monolayers, structural and magnetic characterization strategies, the present status of device exploration, and the principal barriers to realizing intrinsic magnetic Janus monolayers are discussed. By distinguishing experimentally demonstrated capabilities from theoretical predictions, this review provides a structured reference for the development of future spintronic, valleytronic, and topological devices.
