Condensed Matter

2012 Submissions

[2] viXra:2012.0227 [pdf] submitted on 2020-12-31 10:58:09

Boron Content and the Superconducting Critical Temperature of Carbon-Based Materials

Authors: Nadina Gheorghiu, Charles R. Ebbing, Timothy J. Haugan
Comments: 6 Pages.

In this paper, we present results on magnetization properties of boron nitride-carbon (BN-C) and boron carbide-carbon (B4C-C) granular mixtures. The temperature-dependent magnetization for field-cooled during cooling and field-cooled during warming shows a kind of thermal hysteresis that is always seen around a metamagnetic phase transition from an antiferromagnetic martensite to a ferromagnetic austenite phase. The low-temperature magnetization has an upward turn that can be attributed to superparamagnetism, diamagnetic shielding, and trapped flux characteristic to high-temperature superconducting materials. After subtracting the diamagnetic background, the field-dependent magnetization loops M(B) are ferromagnetic-like, more significant for the BN-C than for the B4C-C mixture. In addition, the magnetization loops show the kink feature characteristic to granular superconductivity. The irreversibility temperature for a B4C-C mixture having 37.5 wt% B is Tc  76 K. Combining our data with previous results on B-doped diamond and Q-carbon, we find that Tc increases linearly with the B concentration.
Category: Condensed Matter

[1] viXra:2012.0019 [pdf] submitted on 2020-12-04 08:34:13

Neutron-Scattering Determination of Phonon Wave Function and Topological Invariant in Transition-Metal Monosilicides

Authors: Zhendong Jin, Biaoyan Hu, Yiran Liu
Comments: 6 Pages.

In close analogy to electronic semimetals, a variety of Weyl, Dirac points and nodal lines are predicted for phonons recently by ab initio calculations, but very few experimental confirmations have been made. We performed Inelastic Neutron Scattering (INS) experiments on MnSi and CoSi crystals, and identified multiple types of unconventional Weyl and Dirac points in their Brillioun zones. Being aware of neutron scattering's capability of wavefunction detection and polarization determination, we further derived an explicit relation between the topological invariant of a Weyl node and the INS intensity patterns nearby. Apart from protected surface states and novel transport phenomena, our work suggests that topological nodes also leave some observable traces in spectroscopic patterns.
Category: Condensed Matter