Chapter 5 Superconductivity in Semiconductors and Semi-Metals

Hülm, J. K.; Ashkin, M.; Deis, D. W.; Jones, C. K.

doi:10.1016/s0079-6417(08)60064-5

Cited by 52 publications

(35 citation statements)

References 62 publications

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“…Hund coupling and reduced band filling resulting from multiple bands is likely to diminish possibility of singlet superconductivity. It will be also interesting to look for new systems and also find out if electron correlation play any important role in estabilishing superconductivity in known impurity band superconductors [17] I thank Prof S Maekawa for bringing to my attention reference [1], Prof. S Maekawa and Prof H Fukuyama for discussion, hospitality and IFCAM Visiting Professorship at Sendai. An informative discussion on spectrosopy of boron acceptor states in diamond with Prof A K Ramdas in February 2004 is acknowledged.…”

Section: Pacs Numbersmentioning

confidence: 99%

Resonating Valence Bond Mechanism of Impurity Band Superconductivity in Diamond

Baskaran

2007

J Supercond Nov Magn

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Superconductivity in an uncompensated boron doped diamond, a very recent observation, is strikingly close to an earlier observation of Anderson-Mott insulator to metal transition, prompting us to suggest an electron correlation driven superconductivity in an impurity band. Random coulomb potential remove a three fold orbital degeneracy of boron acceptor states, resulting in an effective single, narrow, tight binding and half filled band of holes. Singlet coupling between spins of neighboring neutral acceptors B 0 − B 0 is the seed of pairing. Across the insulator to metal transition, a small and equal fraction of charged B + and B − states (free carriers) get spontaneously generated and delocalize. Thereupon neutral singlets resonate and get charged resulting in a resonating valence bond (RVB) superconducting state.

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Section: Pacs Numbersmentioning

confidence: 99%

Resonating Valence Bond Mechanism of Impurity Band Superconductivity in Diamond

Baskaran

2007

J Supercond Nov Magn

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“…Increasing the concentration to 10 20 cm −3 gradually decreases the activation energy 9,10 , and for n≥10 20 cm −3 , the electrical conductivity acquires metallic-like behaviour near room temperature [8][9][10][11] that signals an insulator-metal transition near this concentration. A metallic-like conductivity has not been found, however, at low temperatures for any presently available B concentration, which has reached (2-3)×10 21 cm −3 (refs 8-11).…”

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Superconductivity in diamond

Екимов

Sidorov

Bauer

et al. 2004

Nature

1,070

690

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Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields 1 . With these physical properties, diamond is attractive for electronic applications 2 , particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond 3 ; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (8-9 GPa) and temperature (2,500-2,800 K).Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature T c ≈4 K; superconductivity survives in a magnetic field up to H c2 (0)≥3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.With their potential for electronic applications as microchip substrates, high efficiency electron emitters, photodetectors and transistors, diamond and carrier-doped diamond have been studied extensively 3-6 . The extremely short covalent bonds of carbon atoms in diamond give diamond many of its desirable properties, but also constrain geometrically which dopants can be incorporated and their concentration. Because of its small atomic radius compared to other potential dopants, boron is readily incorporated into the dense (1.763×10 23 atoms cm −3 ) diamond lattice. Boron dopes holes into a shallow acceptor level close to the top of the valence band that is separated from the conduction band of diamond by E g ≈5.5 eV. Electrical transport studies of B-doped diamond, including high-pressure synthesized crystals and CVD (chemical vapour deposition) films, find that low boron concentrations n≈10 17 -10 19 cm −3 give a semiconducting conductivity with an activation energy of ~0.35 eV (refs 7-11). Increasing the concentration to 10 20 cm −3 gradually decreases the activation energy 9,10 , and for n≥10 20 cm −3 , the electrical conductivity acquires metallic-like behaviour near room temperature [8][9][10][11] that signals an insulator-metal transition near this concentration. A metallic-like conductivity has not been found, however, at low temperatures for any presently available B concentration, which has reached (2-3)×10 21 cm −3 (refs 8-11).We have studied B-doped diamond synthesized by reacting B 4 C and graphitic carbon at pressure, 8-9 GPa, and temperature, 2,500-2,800 K, for ~5 s. Under these conditions, polycrystalline diamond aggregates 1-2 mm in size formed at the interface between graphite and B 4 C. All the diamond aggregates had a metal-like lustre. Scanning electron microscopy (SEM) showed that the di...

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“…Finally, the behavior of T c as a function of carrier concentration in doped STO is different from that of conventional low carrier superconductors for which T c increases monotonically with the carrier concentration. 17 In STO, T c first increases with the carrier concentration n then, for n larger than 1ϫ10 20 cm Ϫ3 , T c goes down, with superconductivity vanishing around 1ϫ10 21 cm Ϫ3 . It is generally accepted that this behavior can be explained by the plasmon and polar optic phonon model.…”

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Electrostatic modulation of the electronic properties of Nb-doped SrTiO3 superconducting films

Takahashi

Matthey

Jaccard

et al. 2004

Applied Physics Letters

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We have performed ferroelectric field effect experiments using an epitaxial heterostructure composed of ferroelectric Pb(Zr0.2Ti0.8)O3 and superconducting Nb-doped SrTiO3. The films were prepared on (001) SrTiO3 substrates by off-axis radio-frequency magnetron sputtering and pulsed-laser deposition. By switching the polarization field of the 500-Å-thick Pb(Zr0.2Ti0.8)O3 layer, a large change of about 30% in resistivity and a 20% shift of Tc (ΔTc∼0.05 K) were induced in the 400-Å-thick epitaxial Nb-doped SrTiO3 layer. The relationship between Tc and the electrostatically modulated average carrier concentration can be mapped onto the phase diagram of chemically doped SrTiO3.

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Chapter 5 Superconductivity in Semiconductors and Semi-Metals

Cited by 52 publications

References 62 publications

Resonating Valence Bond Mechanism of Impurity Band Superconductivity in Diamond

Resonating Valence Bond Mechanism of Impurity Band Superconductivity in Diamond

Superconductivity in diamond

Electrostatic modulation of the electronic properties of Nb-doped SrTiO3 superconducting films

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