Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0105157

A search for incipient lattice instabilities in MgB$_{2}$ by anelastic spectroscopy

F. Cordero·R. Cantelli·G. Giunchi·S. Ceresara
View original source ↗Read source document ↗Export metadata ↓

Abstract

We measured the complex dynamic elastic modulus of MgB2 between 1.3 and 650 K at frequencies included between 5 and 70 kHz. The main purpose of this work is to search for possible lattice instabilities, which could contribute to enhance the electron-phonon coupling. The Young's modulus indeed presents an anomalous softening on cooling below 400 K, and hysteresis between cooling and heating. Such anomalies, however, can be accounted for by intense relaxation processes with maxima between 50 and 150 K, whose nature is not yet clarified, and by geometric defects generated by the anisotropic thermal expansion between the grains during thermal cycling. Additional intense relaxation processes are observed above room temperature, and their possible origin is discussed. The influence of the highly anharmonic in-plane vibration modes of the B atoms on the elastic and anelastic properties of MgB2 is discussed in detail.

Explore related subjects

cond-mat.supr-con

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

F. Cordero, R. Cantelli, G. Giunchi, S. Ceresara. 2001-05-08. A search for incipient lattice instabilities in MgB$_{2}$ by anelastic spectroscopy. https://doi.org/10.1103/physrevb.64.132503

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Field-induced first order quantum phase transition of the superconducting order parameter in Ising superconductors with Rashba spin-orbit coupling

Ising superconductors have attracted significant attention recently due to their resilience against magnetic fields far beyond the Pauli-paramagnetic limit as well as their broader role as a platform for exploring the interplay of spin-orbit coupling, valley degrees of freedom and superconducting pairing in two-dimensional materials. Their protection against external magnetic field relies on strong Ising spin-orbit coupling, which originates from in-plane inversion symmetry breaking. Due to the heavy atom nature of Ising SCs, a smaller but sizable Rashba SOC can arise from gating or interfacial effects. Here, we study Rashba spin-orbit coupling within a two-valley model of Ising superconductors with an attractive $s$-wave interaction. We show that Rashba SOC induces a first order quantum phase transition in Ising superconductors. At low temperatures, this means the superconducting order parameter vanishes abruptly in the vicinity of the quantum critical point. This effect, however, disappears at high temperatures. Our findings demonstrate that the low- and high temperature physics of Ising SCs are quantitatively and qualitatively different in the two-valley model.

cond-mat.supr-con↗
arXiv2026

Nonlocal Cooper pairs in finite topological superconductors and their relation to Majorana nonlocality

We identify two fundamental properties of the Gor'kov Green's function of finite one-dimensional topological superconductors. In the low-frequency (low-energy) regime, the normal and anomalous Green's functions become identical up to a phase factor. Moreover, they exhibit pronounced nonlocality: the components connecting the two ends of the system grow exponentially with system length, whereas the local components at either end vanish in the zero-frequency limit. These striking features signify the emergence of unconventional nonlocal Cooper pairs associated with a nonlocal fermionic mode composed of hybridized Majorana end modes. The nonlocal Cooper pairs are directly linked to fermion parity and to the nonlocal transport properties of finite topological superconductors. By uncovering the unusual nonlocal properties of the Gor'kov Green's function, our analysis advances the understanding of Majorana nonlocality, a key concept in topological quantum computation.

cond-mat.supr-con↗
arXiv2026

Collective phase modes in twisted $d$-wave superconducting bilayers

Twisted cuprate bilayers have been predicted to host high-temperature chiral $d+id'$ superconductivity, originating from higher-order Josephson coupling processes. In such two-dimensional superconducting systems, long-wavelength fluctuations in the phase of the superconducting order parameter constitute gapless collective modes and therefore remain significant even at zero temperature. Here, we perform a theoretical analysis of the low-energy phase fluctuations in twisted $d$-wave superconducting bilayers within a self-consistent harmonic approximation, systematically retaining Josephson coupling to all orders. We demonstrate that higher-order Josephson coupling processes lead to nontrivial modifications of the phase dynamics. The momentum-resolved summand of the relative-phase stiffness is nonzero even in the normal state because interlayer tunneling explicitly breaks the intralayer U(1) symmetry, but its momentum integral vanishes for the continuum dispersion. The relative-phase stiffness is smaller in the $d+id'$ phase than in the $d$-wave phase, while the overall-phase stiffness has the opposite behavior. Furthermore, phase fluctuations strongly soften the Josephson plasma frequency near a twist angle of $45^\circ$ and also substantially reduce the Josephson critical current.

cond-mat.supr-con↗