Interplay between structure and superconductivity: Metastable phases of phosphorus under pressure

Abstract

Pressure-induced superconductivity and structural phase transitions in phosphorus (P) are studied by resistivity measurements under pressures up to 170 GPa and by fully ab initio crystal structure exploration and superconductivity calculations up to 350 GPa. Two distinct superconducting transition temperature (T C ) vs pressure (P ) trends at low pressure have been reported more than 30 years ago, and we are able to devise a consistent explanation founded on thermodynamically metastable phases of black phosphorus. Our experimental and theoretical results form a single, consistent picture which not only provides a clear understanding of elemental P under pressure but also sheds light on the longstanding and unsolved anomalous superconductivity trends. Moreover, at higher pressures we predict a similar scenario of multiple metastable structures which coexist beyond their thermodynamical stability range. We observe that all the metastable structures systematically exhibit larger transition temperatures than the ground-state structures, indicating that the exploration of metastable phases represents a promising route to design materials with improved superconducting properties.

A perspective on conventional high-temperature superconductors at high pressure: Methods and materials

“…A substantial amount of computational studies have been published and in some of them spectacular values close or above room temperature have been predicted [176,177]. Many other systems have been theoretically proposed to form superhydrides, reviving also the interest in structural transformations of individual elements and their tendency to form metallic structures [63,178,54,179,74]. Experimentally, superconductivity in hydrides under pressure has been confirmed to occur Less than one year ago (2018), the work on H-rich compositions in the La-H system set a new superconducting record, since it represents the first measurement of T c near room temperature.…”

A Critical Review of Machine Learning of Energy Materials

“…Superconductivity describes electrical charge flow inside a material without resistance. Finding high‐temperature, ideally, room‐temperature, superconductors is of profound importance to the society on many aspects including reducing the electrical energy loss during transmission as well as saving the electricity waste in everyday appliances . Improvements in first‐principles calculations of electron–phonon spectra have made it possible to predict the critical temperature T cr in silico.…”

Kondo-semimetal to Fermi-liquid phase crossover in black phosphorus to pressure-induced orbital-nematic gray phosphorus

“…In practice however, it is very difficult to separate the effects of the hopping from those induced by crystal field splittings, even more so if lattice instabilities under pressure or negative pressure are not known a priori. Accordingly, since a semimetal-to-metal crossover which is likely to exist in the metastable phases [3] of phosphorus at low pressures, we adopt the following strategy to derive this crossover. Instead of actually lifting orbital degeneracy by uniaxial compression, we search for an instability of the semimetal phase to the paramagnetic Fermi liquid metal.…”

“…This in our opinion reinforces the basic hypothesis about the interplay between structural distortions (inducing changes in crystal field splitings) and sizable MO many-body correlations in bulk p band systems [53]. Given the large dynamical spectral weight transfer characteristic of correlated electron systems, orbital nematicity (or the lifting of the twofold orbital degeneracy within the x,y orbitals of GP) can be expected to have a sensible impact on correlated semiconductors and semimetals in close proximity to electronic [15] and metastable structural phase transformations [3]. The generic appearance of metallic states and the instabilities of such states to, for example, unconventional superconductivity [3] makes this a very important question worth investigating, which may open scenarios on pressurized BP.…”

“…1. Despite its classic status as an element [2], phosphorus remains surprising due to fascinating structure/property relationships hosted by this layered p-band material [3]. Particularly interesting are strain-induced band gap modifications [4][5][6], which allows us to tune semiconductor BP into anisotropic Dirac semimetal [7], and a superconducting phase transition induced by pressure [8].…”