High-TC Superconductivity Originating from Interlayer Coulomb Coupling in Gate-Charged Twisted Bilayer Graphene Moiré Superlattices

Harshman, Dale R.; Fiory, A. T.

doi:10.1007/s10948-019-05183-9

Cited by 11 publications

(12 citation statements)

References 90 publications

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“…29 19 Im m H 3 S (155 GPa), 17 HgBa 2 Ca 2 Cu 3 O 8+ (25 GPa), 18 YBa 2 Cu 3 O 8 (12 GPa), 18 A15 Cs 3 C 60 (0.93 GPa), 20 FeSe 0.977 (7.5 GPa), 31 Fe 1.03 Se 0.57 Te 0.43 (2.3 GPa), 31 and C/C (twisted bilayer graphene device D2, 1.33 GPa). 32 The solid line represents Eq. ( 1), highlighting the equality between T C and T C0 .…”

Section: Experimental Data For C-s-h Indicate Limitations On the Superconducting Statesmentioning

confidence: 99%

“…1 is plotted against calculated T C0 for I 3m CSH 7 at P = 267 GPa, and compared to T C vs. T C0 for several other optimally-compressed high-T C superconductors at the pressures indicated. [17][18][19][20]31,32 The solid line represents Eq. ( 1) and highlights the equality between measurements of T C and calculations of T C0 , with remarkable concurrence between theory and experiment exhibited over a range in T C covering nearly 300 K. A key takeaway from Fig.…”

Section: Experimental Data For C-s-h Indicate Limitations On the Supe...mentioning

confidence: 99%

“…4. Measured T C vs. calculated T C0 for compressed high-T C superconductors; I 3m CSH 7 (267 GPa), Fm m LaH 10 (169 and 192 GPa),19 Im m H 3 S (155 GPa),17 HgBa 2 Ca 2 Cu 3 O 8+ (25 GPa),18 YBa 2 Cu 3 O 8 (12 GPa),18 A15 Cs 3 C 60 (0.93 GPa),20 FeSe 0.977 (7.5 GPa),31 Fe 1.03 Se 0.57 Te 0.43 (2.3 GPa),31 and C/C (twisted bilayer graphene device D2, 1.33 GPa) 32. The solid line represents Eq.…”

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confidence: 99%

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The superconducting transition temperatures of C–S–H based on inter-sublattice S−H4-tetrahedron electronic interactions

Harshman

Fiory²

2022

Journal of Applied Physics

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Significant characteristics of the superconducting transitions reported for carbonaceous sulfur hydride [Snider et al., Nature 585, 373 (2020)] are the exceptionally abrupt onset temperatures and their marked increase toward room temperature at high pressure. Theoretical and experimental studies addressing the superconducting composition and structure have thus far returned mixed results. One possibility, consistent with the experimentally suggested stoichiometry of CSH x , is the theoretically-discovered compressed I 3m CSH 7 structure [Sun et al., Phys. Rev. B 101, 174102 (2020)], which comprises a sublattice similar to Im m H 3 S with CH 4 intercalates. Positing an electronic genesis of the superconductivity, a model is presented in analogy with earlier work on superconductivity in Im m H 3 S, in which pairing is induced via purely electronic Coulomb interactions across the mean distance ζ between the S and H 4 tetrahedra enclosing C. Theoretical superconducting transition temperatures for I 3m CSH 7 are derived as T C0 = (2/3) 1/2  1/2 /aζ, where  = 1247.4 Å 2 K is a universal constant,  is the participating charge fraction, and a is the lattice parameter. Analysis suggests persistent bulk superconductivity with a pressure-dependent , increasing from  = 3.5, determined previously for Im m H 3 S, to  = 7.5 at high pressure owing to additionally participating C-H bond electrons. With a and ζ determined by theoretical structure, T C0 = 283.6  3.5 K is predicted at 267  10 GPa, in excellent agreement (within uncertainty) with the corresponding experimental T C = 287.7  1.2 K. Pressure-induced variations in  combined with experimental uncertainties in pressure yield overall average (T C  T C0 ) = (0.8  3.5) K.

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Section: Experimental Data For C-s-h Indicate Limitations On the Superconducting Statesmentioning

confidence: 99%

Section: Experimental Data For C-s-h Indicate Limitations On the Supe...mentioning

confidence: 99%

mentioning

confidence: 99%

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The superconducting transition temperatures of C–S–H based on inter-sublattice S−H4-tetrahedron electronic interactions

Harshman

Fiory²

2022

Journal of Applied Physics

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“…Superconductive pairing in high-T C superconductors is successfully modeled by Coulomb interactions between charges in spatially separated charge reservoirs [40,41,[49][50][51][52][53][54][55].…”

Section: Coulomb-mediated Superconductivity In Mh Nmentioning

confidence: 99%

“…Developed initially to describe indirect Coulombic pairing interactions between charges in adjacent extended layers, this unique theory is also applicable to extended three-dimensional (3D) lattices, such as the compressed phases of Cs 3 C 60 [49] and H 3 S [41], in which charges are similarly separated into two reservoirs. To date, this approach has been validated with statistical accuracy of ±1.30 K (or ±4%) in T C0 for 53 different materials from ten disparate superconducting families; the aforecited 3D compounds [41,49], layered cuprates, ruthenates, rutheno-cuprates, iron pnictides, BEDT-based [bis(ethylenedithio)tetrathiafulvalene] organics [40,50,51], iron chalcogenides [52], intercalated group-4-metal nitride halides [53,54] and gated twisted bilayer graphene [55], with measured T C0 values ranging from ~2 to 200 K. Optimization resulting in a maximum transition temperature is typically accomplished via doping and/or pressure-induced charge transfer.…”

Section: Coulomb-mediated Superconductivity In Mh Nmentioning

confidence: 99%

High-TC Superconductivity in Hydrogen Clathrates Mediated by Coulomb Interactions Between Hydrogen and Central-Atom Electrons

Harshman

Fiory

2020

J Supercond Nov Magn

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The uniquely characteristic macrostructures of binary hydrogen-clathrate compounds MH n formed at high pressure, a cage of hydrogens surrounding a central-atom host, is theoretically predicted in various studies to include structurally stable phonon-mediated superconductors. High superconductive transition temperatures T C have thus far been measured for syntheses with M = La, Y, and Th. In compressed LaH 10 , independent studies report T C of 250 K and over 260 K, a maximum in T C with pressure P, and normal-state resistance scaling with temperature (suggesting unconventional pairing). According to reported band structure calculations of Fm m-phase LaH 10 , the La is anionic, with the chemical valence electrons appearing evenly split between La and H 10 . Thus, compressed LaH 10 contains the combination of structure, charge separation and optimal balanced allocation of valence electrons for supporting unconventional high-T C superconductivity mediated by Coulomb interactions between electronic charges associated with La and H 10 . A general expression for the optimal superconducting transition temperature for MH n clathrates is derived as T C0 = k B 1 [(n + v)/2A] 1/2 e 2 /ζ, where  is a universal constant, (n + v) is the chemical valence sum per formula unit, taking unity for H and v for atom M, A is the surface area of the H-polyhedron cage, and  is the mean distance between the M site and the centroids of the polyhedron faces. Applied to Fm m LaH 10 , T C0 values of 249.8(1.3) K and 260.7(2.0) K are found for the two experiments. Associated attributes of charge allocation, structure, effective Coulomb potential, and H-D isotope effect in T C of Fm m LaH 10 and Im m H 3 S are discussed, along with a generalized prospective for Coulomb-mediated superconductivity in MH n . 1 The layered FeH 5 , synthesized with no demonstration of superconductivity [32], is predicted to be superconducting in [33,34] and non-superconducting in [35]. 2 Note that here is a typographical error at the end of Section 3 (p. 5) of [41] which should read, "ℓ = (A/) 1/2 = 2.88 Å," with the reported T C0 remaining unchanged.

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Moiré‐Pattern‐Tuned Electronic Structures of van der Waals Heterostructures

Tang

2020

Adv Funct Materials

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Moiré patterns are quasi‐periodic geometric patterns generated by the incommensurate stacking between two monolayers; they have rapidly attracted enormous attention due to their profound ability to modulate the electronic properties of 2D materials. For instance, the Bloch band of the Moiré superlattice, which is known as the Moiré band, can become flat at a specific series of discrete angles, and these flat bands are capable of exhibiting strong correlation behaviors such as the high‐temperature superconductivity reported recently. Moiré patterns can alter electronic properties, while surface reconstruction can modify Moiré patterns. In this review, the fundamental geometry is discussed and the basic electronic structure modification is summarized. Surface reconstruction is a method of tuning the electronic properties of a Moiré superlattice. Strong correlation phenomena, such as superconductivity, superfluidity, and magnetism induced by the flat bands, have been confirmed experimentally in recent years, which will be discussed in detail. Some possible application opportunities based on the fascinating characteristics of the Moiré pattern will also be presented. Because of the growing interest in Moiré patterns and related physical phenomena, it is anticipated that a deeper understanding of the fundamental physics of Moiré systems and further progress in the investigation of strong correlation phenomena are forthcoming.

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High-TC Superconductivity Originating from Interlayer Coulomb Coupling in Gate-Charged Twisted Bilayer Graphene Moiré Superlattices

Cited by 11 publications

References 90 publications

The superconducting transition temperatures of C–S–H based on inter-sublattice S−H4-tetrahedron electronic interactions

The superconducting transition temperatures of C–S–H based on inter-sublattice S−H4-tetrahedron electronic interactions

High-TC Superconductivity in Hydrogen Clathrates Mediated by Coulomb Interactions Between Hydrogen and Central-Atom Electrons

Moiré‐Pattern‐Tuned Electronic Structures of van der Waals Heterostructures

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