Phase transition from a dx2−y2 to dx2−y2+idxy superconductor

Ghosh, Angsula; Adhikari, Sadhan K.

doi:10.1016/s0921-4534(98)00585-1

Cited by 13 publications

(13 citation statements)

References 30 publications

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“…We have also studied the temperature dependence of the order parameter under different situations. This temperature dependence is quite similar to the n = 1 case studied by us previously [34,35]. We also studied the dependence of the critical temperature T c for the mixed-symmetry state on filling n under different situations and find that this dependence exhibits a maximum and rapid variation.…”

Section: Discussionsupporting

confidence: 81%

“…From both experimental observations [2][3][4][5][6] and related theoretical analyses [7][8][9][10][11][12][13][14] there is a consensus that immediately below T c , the symmetry of the order parameter is of the d x 2 −y 2 type. However, many experiments [15][16][17][18][19][20][21][22][23][24] and theoretical analyses [25,26,[28][29][30][31][32][33][34][35][36][37][38][39][40] suggest that at lower temperatures the order parameter has a mixed symmetry of the d x 2 −y 2 + exp(iθ)χ type, where χ represents a minor-component state with a distinct symmetry superposed on the major component d x 2 −y 2 . From theoretical analysis the mixing angle θ can have the values 0, π/2, π, and 3π/2.…”

Section: Introductionmentioning

confidence: 99%

“…In the absence of a microscopic theory, we use a phenomenological two-dimensional tight-binding model with appropriate lattice symmetry for studying some of the general features of the mixed-symmetry states of overdoped high-T c superconductors where there is no pseudo gap. This model has been used successfully in describing many properties of high-T c materials [25,26,[28][29][30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

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Mixing of dx2−y2 and dxy superconducting states for different filling and temperature

Ghosh

Adhikari

2002

Physica C: Superconductivity

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We investigate the solution of the gap equation for mixed order parameter symmetry states as a function of filling using a two-dimensional tight-binding model incorporating second-neighbor hopping for tetragonal and orthorhombic lattice. The principal (major) component of the order parameter is taken to be of the d x 2 −y 2 type. As suggested in several investigations the minor component of the order parameter is taken to be of the d xy type. Both the permissible mixing angles 0 and π/2 between the two components are considered. As a function of filling pronounced maxima of d x 2 −y 2 order parameter is accompanied by minima of the d xy order parameter. At fixed filling, the temperature dependence of the two components of the order parameter is also studied in all cases. The variation of critical temperature T c with filling is also studied and T c is found to increase with second-neighbor hopping. PACS # 74.20.Fg, 74.25.Bt.

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Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mixing of dx2−y2 and dxy superconducting states for different filling and temperature

Ghosh

Adhikari

2002

Physica C: Superconductivity

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“…21(b)]. Interestingly it has been demonstrated that such behavior can arise from the self-consistent BCS gap equation for d x 2 −y 2 + id xy 64 or d x 2 −y 2 + is 65 symmetries. Moreover an intermediate s + is symmetry has been proposed in Ba 1−x K x Fe 2 As 2 for x between 0.4 and 1.0.…”

Section: Three-band α-Model Fitsmentioning

confidence: 99%

Electronic specific heat of Ba1−xKxFe2As
Storey
¹
,
Loram
²
,
Cooper
³

et al. 2013
Phys. Rev. B
46
8
54
1
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Using a high-resolution differential technique we have determined the electronic specific heat coefficient γ (T ) = C el /T of Ba 1−x K x Fe 2 As 2 with x = 0 to 1.0, at temperatures (T ) from 2 K to 380 K and in magnetic fields H = 0 to 13 T. In the normal state γ n (x,T ) increases strongly with x at low temperature, compatible with a mass renormalization ∼12 at x = 1, and decreases weakly with x at high temperature. A superconducting transition is seen in all samples from x = 0.2 to 1, with transition temperatures and condensation energies peaking sharply at x = 0.4. Superconducting coherence lengths ξ ab ∼ 20Å and ξ c ∼ 3Å are estimated from an analysis of Gaussian fluctuations. For many dopings we see features in the H and T dependencies of γ s (T ,H ) in the superconducting state that suggest superconducting gaps in three distinct bands. A broad "knee" and a sharp mean-field-like peak are typical of two coupled gaps. However, several samples show a shoulder above the sharp peak with an abrupt onset at T c,s and a T dependence γ s (T ) ∝ 1 − T /T c,s . We provide strong evidence that the shoulder is not due to doping inhomogeneity and suggest it is a distinct gap with an unconventional T dependenceWe estimate band fractions and T = 0 gaps from three-band α-model fits to our data and compare the x dependencies of the band fractions with spectroscopic studies of the Fermi surface.The electronic specific heat γ measured to room temperature contains a wealth of quantitative information about the electronic spectrum of metallic systems over an energy region ±100 meV about the Fermi level, crucial for understanding high-temperature superconductivity. Measurements of the electronic specific heat have played an important role in revealing key properties of the copper-oxide-based "cuprate" high-temperature superconductors (HTSCs). Some examples include the normal-state "pseudogap," 1-4 the bulk sample inhomogeneity length scale, 5 and more recently evidence that the superconducting transition temperature is suppressed due to superconducting fluctuations. 6 In this work we extend such measurements to the iron-arsenide-based "pnictide" HTSCs. Here we present results obtained for polycrystalline samples of Ba 1−x K x Fe 2 As 2 (x = 0 to 1.0) using a high-resolution differential technique. 7 With this technique we directly measure the difference in the specific-heat capacities of a doped sample and an undoped reference sample (BaFe 2 As 2 ). This eliminates most of the large phonon term from the raw data and yields a curve dominated by the difference in electronic terms. Features of the electronic specific heat that would otherwise be masked by the large phonon background are then clearly visible in the raw data over the entire temperature range. Central to the success of this technique are measurements on a series of samples at closely spaced doping intervals, so that systematic trends in the the relatively small difference in phonon terms between sample and reference can be identified and appropriate corrections made. ...

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“…The temperature dependence of the various thermodynamic quantities and transport properties change from power lows to exponential below T c1 . [9,10] When the secondary order parameter is not strong enough, only the d x 2 −y 2 -wave order parameter appears in the bulk. For (110) surfaces the d x 2 −y 2 -wave order parameter changes sign under reflection at the surface and vanishes at the surface.…”

Section: Introductionmentioning

confidence: 99%

Tunnelling spectra for (d_x²-y²+ is)-wave superconductors versus tunnelling spectra for (d_x²-y²+ id_xy)-wave superconductors

Stefanakis

2001

J. Phys.: Condens. Matter

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The tunnelling conductance spectrum of a normal-metal/insulator/singlet super-conductor is calculated from the reflection amplitudes using the Blonder-Tinkham-Klapwijk (BTK) formulation. The pairing symmetry of the superconductor is assumed to be dx2-y2 + is or dx2-y2 + idxy. It is found that in the (dx2-y2 + is)-wave case there is a well defined conductance peak in the conductance spectra, in the amplitude of the secondary s-wave component. In the (dx2-y2 + idxy)-wave case the tunnelling conductance has residual values within the gap, due to the formation of bound states. The bound-state energies depend on the angle of the incident quasiparticles, and also on the boundary orientation. On the basis of this observation, an electron-focusing experiment is proposed to probe the (dx2-y2 + idxy)-wave state.

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Phase transition from a dx2−y2 to dx2−y2+idxy superconductor

Cited by 13 publications

References 30 publications

Mixing of dx2−y2 and dxy superconducting states for different filling and temperature

Mixing of dx2−y2 and dxy superconducting states for different filling and temperature

Electronic specific heat of Ba1−xKxFe2As
Storey
¹
,
Loram
²
,
Cooper
³

et al. 2013
Phys. Rev. B
46
8
54
1
View full text Add to dashboard Cite

Tunnelling spectra for (d_x²-y²+ is)-wave superconductors versus tunnelling spectra for (d_x²-y²+ id_xy)-wave superconductors

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Phase transition from a dx2−y2 to dx2−y2+idxy superconductor

Cited by 13 publications

References 30 publications

Mixing of dx2−y2 and dxy superconducting states for different filling and temperature

Mixing of dx2−y2 and dxy superconducting states for different filling and temperature

Electronic specific heat of Ba1−xKxFe2AsStorey1, Loram2, Cooper3 et al. 2013Phys. Rev. B468541View full textAdd to dashboardCite

Tunnelling spectra for (dx2-y2+ is)-wave superconductors versus tunnelling spectra for (dx2-y2+ idxy)-wave superconductors

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Product

Resources

About

Electronic specific heat of Ba1−xKxFe2As
Storey
¹
,
Loram
²
,
Cooper
³

et al. 2013
Phys. Rev. B
46
8
54
1
View full text Add to dashboard Cite

Tunnelling spectra for (d_x²-y²+ is)-wave superconductors versus tunnelling spectra for (d_x²-y²+ id_xy)-wave superconductors