The pseudogap state in high- superconductors: an infrared study

Puchkov, A. V.; Basov, D. N.; Timusk, T.

doi:10.1088/0953-8984/8/48/023

Cited by 412 publications

(549 citation statements)

References 122 publications

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“…Although not shown here, we observe that the phase fluctuations in the SU(2) cause a substantial reduction in the width of the Drude peak compared to the U(1) result but the position of the hump remains nearly identical. The SU(2) result is in closer agreement with observations [3,4] compared to the U(1) case. On the other hand, the height of the hump is found to be lower in the SU(2) case as compared to the U(1) case.…”

Section: B Optical Conductivity In U(1) and Su(2) Slave-boson Theoriessupporting

confidence: 88%

“…Here we would like to point out that the predicted trend of both the shift of the hump position to lower frequency and the growth of the hump peak height with increasing hole concentration is consistent with observations [21,22]. However, quantitative results in hump position shift and hump peak height fail to agree with observations [3,4]. To thoroughly examine the origin of the peak-dip-hump structure, below we discuss predictions made by systematic changes of various phase fluctuation modes of α , β, and θ.…”

Section: B Optical Conductivity In U(1) and Su(2) Slave-boson Theoriessupporting

confidence: 71%

“…This strong correlation results in the peak-dip-hump structure of the optical conductivity σ(ω) and linear frequency dependence of the scattering rate 1/τ (ω) [1][2][3][4][5][6]. Both the appearance of the hump(which occurs at ω ≈ 1000cm −1 in YBCO [3,4] and Bi2212 [6]) and the linear frequency dependence of the scattering rate(1/τ (ω) ∼ ω) indicate strong deviations from the Drude model prediction of conventional Fermi-liquid. Various theories have been proposed to explain these non-Fermi-liquid(NFL) like behavior in the charge dynamics(optical conductivity) of the high T C cuprates.…”

Section: Introductionmentioning

confidence: 98%

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Origin of the hump structure in the in-plane optical conductivity of high-TCcuprates based on aSU(2)slave-boson theory

et al. 2004

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An improved version of SU(2) slave-boson approach is applied to study the in-plane optical conductivity of the two dimensional systems of high TC cuprates. We investigate the role of fluctuations of both the phase and amplitude of order parameters on the (Drude) peak-dip-hump structure in the in-plane conductivity as a function of hole doping concentration and temperature. The mid-infrared(MIR) hump in the in-plane optical conductivity is shown to originate from the antiferromagnetic spin fluctuations of short range(the amplitude fluctuations of spin singlet pairing order parameters), which is consistent with our previous U(1) study. However the inclusion of both the phase and amplitude fluctuations is shown to substantially improve the qualitative feature of the optical conductivity by showing substantially reduced Drude peak widths for entire doping range. Both the shift of the hump position to lower frequency and the growth of the hump peak height with increasing hole concentration is shown to be consistent with observations.

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Section: B Optical Conductivity In U(1) and Su(2) Slave-boson Theoriessupporting

confidence: 88%

Section: B Optical Conductivity In U(1) and Su(2) Slave-boson Theoriessupporting

confidence: 71%

Section: Introductionmentioning

confidence: 98%

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Origin of the hump structure in the in-plane optical conductivity of high-TCcuprates based on aSU(2)slave-boson theory

et al. 2004

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“…The most appropriate analysis in this case is in terms of a singlecomponent model where features ͑i͒ and ͑ii͒ are attributed to a single channel centered at zero frequency with a frequencydependent effective mass m*( ) and scattering rate 1/ ( ). 16,17 However, close inspection of the conductivity spectra in Fig. 2 reveals the presence of a weak maximum at 7000 cm Ϫ1 , indicating a contribution of an interband transition.…”

mentioning

confidence: 94%

“…25,16 At high temperature or high energy ( ϾE 3 ) the spin-flip events are no longer forbidden and the scattering rate increases. From the spectra of 1/ ( ) we estimate the value of E 3 to be between 500 and 2000 cm Ϫ1 (60˜250 meV͒.…”

mentioning

confidence: 99%

Charge dynamics in the half-metallic ferromagnetCrO2

et al. 1999

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Infrared spectroscopy is used to investigate the electronic structure and charge carrier relaxation in crystalline films of CrO 2 which is the simplest of all half-metallic ferromagnets. Chromium dioxide is a bad metal at room temperature but it has a remarkably low residual resistivity (Ͻ5 ⍀ cm) despite the small spectral weight associated with free carrier absorption. The infrared measurements show that low residual resistivity is due to the collapse of the scattering rate at Ͻ2000 cm Ϫ1 . The blocking of the relaxation channels at low and T can be attributed to the unique electronic structure of a half-metallic ferromagnet. In contrast to other ferromagnetic oxides, the intraband spectral weight is constant below the Curie temperature. ͓S0163-1829͑99͒14929-4͔Chromium dioxide is one of few binary oxides that are ferromagnetic metals. Acicular powders have long been used in particulate media for magnetic recording, but key aspects of the electronic structure of CrO 2 remain unexplored. Its resistivity dc is unusual: the residual resistivity 0 can be as small 5 ⍀ cm, but above 80 K, dc becomes strongly temperature dependent and exceeds 1000 ⍀ cm above the Curie temperature T C ϭ390 K, 1,2 a value which is beyond the Ioffe-Regel limit. Hence, CrO 2 may be classified as a ''bad metal. '' 3,4 Following the original paper by Schwarz, 5 numerous band structure calculations indicate that CrO 2 is a halfmetallic ferromagnet with completely spin-polarized spin-up electrons at E F and a wide gap in the spin-down density of states ͑DOS͒. 4,6-10 Recently a 90% spin polarization at E F has been measured in CrO 2 using superconducting point contact spectroscopy. 11 Here we investigate the electronic structure and charge dynamics in CrO 2 by means of reflectance spectroscopy carried out over the frequency range from 500 GHz to near ultraviolet. Our experiments reveal an interband contribution to the complex conductivity that is in accordance with a band structure entailing a high degree of spin polarization of the electronic states at E F . A half-metallic density of states implies a temperature-and frequency-dependent intraband scattering rate. The strong suppression of the scattering rate that we observe as , T˜0 is consistent with this notion of a ͑partial͒ gap in the electronic DOS. We have also analyzed the temperature dependence of the electronic spectral weight (N e f f ). In contrast to other ferromagnetic oxides, such as the manganites, we find no variation of N e f f with temperature.We measured the near-normal incidence reflectance R( ) of crystalline films of CrO 2 grown on a TiO 2 ͓110͔ substrate. 2 Films with thickness Ͼ5 m were found to be completely opaque throughout the experimental frequency range 14-37 000 cm Ϫ1 ͑2 -4600 meV͒. Films were coated in situ with gold or aluminum in the optical cryostat and the spectrum of the metal-coated sample was used as a reference. 12 Experimental errors due to diffuse reflectance are minimized with this procedure, allowing reliable absolute values of R( ) to be obtained. ...

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Spectroscopic Studies on the Metal–Insulator Transition Mechanism in Correlated Materials

et al. 2018

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The metal-insulator transition (MIT) in correlated materials is a novel phenomenon that accompanies a large change in resistivity, often many orders of magnitude. It is important in its own right but its switching behavior in resistivity can be useful for device applications. From the material physics point of view, the starting point of the research on the MIT should be to understand the microscopic mechanism. Here, an overview of recent efforts to unravel the microscopic mechanisms for various types of MITs in correlated materials is provided. Research has focused on transition metal oxides (TMOs), but transition metal chalcogenides have also been studied. Along the way, a new class of MIT materials is discovered, the so-called relativistic Mott insulators in 5d TMOs. Distortions in the MO (M = transition metal) octahedron are found to have a large and peculiar effect on the band structure in an orbital dependent way, possibly paving a way to the orbital selective Mott transition. In the final section, the character of the materials suitable for applications is summarized, followed by a brief discussion of some of the efforts to control MITs in correlated materials, including a dynamical approach using light.

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The pseudogap state in high- superconductors: an infrared study

Cited by 412 publications

References 122 publications

Origin of the hump structure in the in-plane optical conductivity of high-TCcuprates based on aSU(2)slave-boson theory

Origin of the hump structure in the in-plane optical conductivity of high-TCcuprates based on aSU(2)slave-boson theory

Charge dynamics in the half-metallic ferromagnetCrO2

Spectroscopic Studies on the Metal–Insulator Transition Mechanism in Correlated Materials

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