Superconducting state of Ca-VII below a critical temperature of 29 K at a pressure of 216 GPa

Sakata, Masafumi; Nakamoto, Yuki; Shimizu, Katsuya; Matsuoka, Toshifumi; Ohishi, Yasuo

doi:10.1103/physrevb.83.220512

Cited by 104 publications

(91 citation statements)

References 23 publications

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“…A superconducting behavior was reported for Ca at 50 GPa and 1.2 K with the superconducting transition temperature increasing linearly with pressure and reaching one of the highest critical temperatures (25 K) among the elements of the periodic table [11,15].…”

Section: Introductionmentioning

confidence: 99%

“…Under further compression, the Ca-V phase (Cmca) transforms to the orthorhombic Ca-VI structure (space group Pnma) at 158 GPa [14]. A possible host-guest structure was reported at 210 GPa [15], although it has been suggested that the structure of this Ca-VII phase could be a 32-atom tetragonal cell (tI 32) [16]. The Ca-VII phase is stable to 241 GPa, the highest pressure achieved experimentally in Ca [15].…”

Section: Introductionmentioning

confidence: 99%

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Phase diagram of calcium at high pressure and high temperature

Anzellini

Errandonea

MacLeod

et al. 2018

Phys. Rev. Materials

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Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Phase diagram of calcium at high pressure and high temperature

Anzellini

Errandonea

MacLeod

et al. 2018

Phys. Rev. Materials

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“…The critical role of the pressure-induced s to d band electron transfer on the structural stability and physical properties, such as superconductivity, of metals has been studied extensively over the years [1][2][3][4]. High pressure structural sequences in 3 rd period metals have also been elucidated when taking into account the lowering and filling under compression of the initially vacant d-band [5,6].…”

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confidence: 99%

In situlattice measurement of the bcc phase boundary in Mg on the principal shock Hugoniot

et al. 2012

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“…Recently, Ca and C, as ordinary elemental solids, have been studied extensively in physical, chemical, and material science fields due to their interesting structural properties when pressure is applied (6)(7)(8)(9)(10). These peculiar physical properties of compressed Ca and C solids have motivated our attention on Cabased dicarbide CaC 2 .…”

mentioning

confidence: 99%

“…In all structures reported above, carbon atoms form isolated dumbbells. Because both Ca and C solids tend to form C-atom network structures at ambient and high pressure (6)(7)(8)(9)(10), it is reasonable and interesting to investigate pressure-induced possibility of polymerization of isolated C 2 dumbbells in CaC 2 . To our knowledge, there are few studies on compressed CaC 2 so far.…”

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confidence: 99%

Pressure-induced superconductivity in CaC ₂

Luo

Zhang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp 2 -, and sp 3 -hybridized bonds. sp 2 -hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using an evolutionary algorithm in conjunction with ab initio method, we found that, under compression, dumbbell carbon in CaC 2 can be polymerized first into 1D chain and then into ribbon and further into 2D graphite sheet at higher pressure. The C2/m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized in a wide pressure range of 15.2-105.8 GPa and then forced into MgB 2 -type phase with wide range stability up to at least 1 TPa. Strong electron-phonon coupling λ in compressed CaC 2 is found, in particular for Immm phase, which has the highest λ value (0.562-0.564) among them, leading to its high superconducting critical temperature T c (7.9∼9.8 K), which is comparable with the 11.5 K value of CaC 6 . Our results show that calcium not only can stabilize carbon sp 2 hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline-earth metal carbides to uncover their peculiar physical properties under extreme conditions. high pressure | metallization H igh pressure, as a crucial thermodynamic parameter, has been emerging as a powerful tool to investigate physical and chemical behavior of materials, especially to explore the evolution of planets, and synthesize or design materials with peculiar properties such as superhardness and superconductivity (1-5). Recently, Ca and C, as ordinary elemental solids, have been studied extensively in physical, chemical, and material science fields due to their interesting structural properties when pressure is applied (6-10). These peculiar physical properties of compressed Ca and C solids have motivated our attention on Cabased dicarbide CaC 2 . In CaC 2 (11, 12) at ambient pressure, experimentally, four temperature-induced modifications were reported, which are the well-known tetragonal room temperature modification CaC 2 I (space group I4/mmm, Z = 2), two lowtemperature monoclinic modifications CaC 2 II (C2/c, Z = 4), and CaC 2 III (C2/m, Z = 4), and cubic high-temperature modification CaC 2 IV (Fm-3m, Z = 4) (12). Theoretically, orthorhombic CaC 2 Immm (Z = 2, referred to as Immm-1 below) structure, monoclinic CaC 2 C2/m (Z = 2, referred to as C2/m-1 below) structure, and trigonal CaC 2 R-3m (Z = 1) structure, were predicted by Kulkarni et al. (13) using a global exploration method based on simulated annealing scheme. In all structures reported above, carbon atoms form isolated dumbbells. Because both Ca and C solids tend to form C-atom network structures at ambient and high pressure (6-10), it is reasonable and interesting to investigate pressure-induced possi...

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Superconducting state of Ca-VII below a critical temperature of 29 K at a pressure of 216 GPa

Cited by 104 publications

References 23 publications

Phase diagram of calcium at high pressure and high temperature

Phase diagram of calcium at high pressure and high temperature

In situlattice measurement of the bcc phase boundary in Mg on the principal shock Hugoniot

Pressure-induced superconductivity in CaC ₂

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Superconducting state of Ca-VII below a critical temperature of 29 K at a pressure of 216 GPa

Cited by 104 publications

References 23 publications

Phase diagram of calcium at high pressure and high temperature

Phase diagram of calcium at high pressure and high temperature

In situlattice measurement of the bcc phase boundary in Mg on the principal shock Hugoniot

Pressure-induced superconductivity in CaC 2

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Pressure-induced superconductivity in CaC ₂