Superconducting nature of the Bi-II phase of elemental bismuth

Abstract

The superconductivity in the Bi-II phase of elemental Bismuth (transition temperature Tc ≃ 3.92 K at pressure p ≃ 2.80 GPa) was studied experimentally by means of the muon-spin rotation as well as theoretically by using the Eliashberg theory in combination with Density Functional Theory calculations. Experiments reveal that Bi-II is a type-I superconductor with a zero temperature value of the thermodynamic critical field Bc(0) ≃ 31.97 mT. The Eliashberg theory approach provides a good agreement with the experimental Tc and the temperature evolution of Bc. The estimated value for the retardation (coupling) parameter kBTc/ω ln ≈ 0.07 (ω ln is the logarithmically averaged phonon frequency) suggests that Bi-II is an intermediately-coupled superconductor.Bismuth is element 83 in the periodic table. It is a brittle metal with a silvery white color. Its complex and tunable electronic structure exhibits many fascinating properties that often defy the expectations of conventional theories of metals. Most notably, measurements on Bismuth provided the first evidence of quantum oscillations and the existence of the Fermi surface, thereby experimentally confirming the underlying paradigm of all modern solid state physics.

Lattice Dynamics Study of Elemental Bismuth under High Pressure

“…However, Khasanov studied recently the superconducting properties of Bi-II at very low temperatures. 45 There are still some controversies concerning the low-T phase diagram of elemental Bi. But the above discussion shows that the Bi-II phase is stabilized when the temperature increases, which means that some additional temperature dependent contribution such as vibrational or electronic entropies can stabilize it against the Bi-I and Bi-III phases.…”

“…40,42 Among the different high pressure phases, the phases stable at low temperatures (phases II, III and V) are superconducting up to 9 K at 8 GPa. 31,[43][44][45] From the above review of the polymorphs of bismuth, one can see that there are still uncertainties about the stability of the different high pressure phases. Using DFT calculations, Haussermann et al 9 have studied the stability and electronic structures of the I, II, III and V phases at 0 K, but did not study the case of the HP-HT Bi-IV and β-Bi phases because their exact crystal structures were not known at that time and have been experimentally determined only recently.…”

“…43,44 The phonon density of states has been calculated for the Bi-II phase very recently. 45 From the experimental point of view, the study of different Bi phases by Raman spectroscopy have already been performed for the low-pressure phases Bi-I [55][56][57][58] and Bi-II. 58 H. Olijnyk et al 58 measured for the first time the Raman spectrum of Bi-II at pressure up to 2.7 GPa, two peaks were observed around 40 cm -1 and 80 cm -1 .…”

Type-I superconductivity in the Dirac semimetal PdTe2 probed by μSR

“…Although a powerful technique, µSR on type-I superconductors has not been explored in much detail. Studies of the intermediate state in elemental superconductors are scarce and concise [25][26][27][28][29][30][31] Here we report transverse field muon spin rotation measurements in the superconducting phase of PdTe 2 . Experiments were performed on a thin disk-like crystal in two configurations: (i ) with the field perpendicular to the plane of the disk (N ⊥ = 0.86) and (ii ) with the field in the plane of the disk (N = 0.08).…”

Coexistence of type-I and type-II superconductivity signatures in ZrB12 probed by muon spin rotation measurements

“…This technique has been widely used to map the phase diagram and study the microscopic properties of the vortex and Meissner state of superconductors [32,33]. Investigations of the intermediate state by μSR have been limited to a few elemental superconductors [34][35][36][37]; however, recently, there has been increased attention in conjunction with the nature of the superconductivity of the noncentrosymmetric BeAu [38,39]. Here, we employed μSR spectroscopy on single crystals of ZrB 12 , mapped the inhomogeneous magnetic field distributions, and identified and characterized the different superconducting states in the H-T phase diagram.…”