Anomalous Reflectivity Oscillation of Layered Manganite La0.5Sr1.5MnO4

Kouyama, Kazuaki; Kubo, Yoshinori; Ema, Kazuhiro; Kuwahara, H.

doi:10.1143/jpsj.76.123702

Cited by 3 publications

(3 citation statements)

References 10 publications

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“…Figure 2 shows the transient reflectivity of the same sample measured at the same experimental conditions but at 50 K. Finer analysis of the data shows that the low temperature transient reflectivity signal was similar in nature as that of room temperature but with additional oscillatory modulations on it. Transient reflectivity measurements on La 0.5 Sr 1.5 MnO at low temperatures showed oscillations in the signal similar to that reported here [9]. However, they have reported that the origin of these oscillations in the transient reflectivity signal is not clear yet.…”

Section: Resultssupporting

confidence: 85%

“…Thus even a film with a growth rate as slow as a few nm/min can cause modulations in the measured ultrafast transient reflectivity signal. We believe that the reflectivity oscillations observed in earlier reports could be due to this film growth phenomenon [9,10]. Our studies on different samples at various temperatures and the reduction in growth rate with time shows that the source of the film formation is due to the residual gases inside the chamber.…”

Section: Discussionsupporting

confidence: 54%

“…Thus, even a slow surface contamination process can modulate the actual signal originating from the ultrafast response of the sample. Transient reflectivity measurements carried out at low temperatures on La 0.5 Sr 1.5 MnO showed oscillations in the signal with an anomalously long time period which is not well understood [9]. Similar periodic modulations were also reported in reflectivity measurements on bulk ZnO [10].…”

Section: Introductionmentioning

confidence: 51%

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Origin of Periodic Modulations in the Transient Reflectivity Signal at Cryogenic Temperatures

Khan,

Chari,

Jayabalan

et al. 2012

Preprint

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Periodic modulations that appear in the low-temperature transient reflectivity signal of a GaAsP/AlGaAs single quantum well is studied. Similar anomalous oscillations are also observed in layered manganite [K. Kouyama et.al. J. Phys. Soc. Jpn. 76:123702(1-3), 2007]. We show that such periodic modulations are caused by changes in the linear reflectivity of the sample during transient reflectivity measurements. Studied carried out on reflectivity of different materials under identical conditions shows that these modulations on the true transient reflectivity signal are caused by condensation of residual gases on the surface of quantum well. Methods to obtain reliable transient reflectivity data are also described.

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Section: Resultssupporting

confidence: 85%

Section: Discussionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 51%

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Origin of Periodic Modulations in the Transient Reflectivity Signal at Cryogenic Temperatures

Khan,

Chari,

Jayabalan

et al. 2012

Preprint

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Modulations in Low-Temperature Transient Reflectivity Measurements

et al. 2014

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Periodic modulations that appear in the low-temperature transient reflectivity signal of a GaAsP / AlGaAs single quantum well is studied. Similar anomalous oscillations are also reported in layered manganite [K. Kouyama et al., J. Phys. Soc. Jpn.76 (2007) 123702(1–3).] We show that such periodic modulations are caused by changes in the linear reflectivity of the sample during transient reflectivity measurements. Studies carried out on reflectivity of different materials under identical conditions show that these modulations on the true transient reflectivity signal are caused by condensation of residual gases on the surface of quantum well. Methods to obtain reliable transient reflectivity data are also described.

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Nuclear Quadrupole Resonance Frequency in Multilayered Cuprates

et al. 2009

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The 63 Cu nuclear quadrupole resonance (NQR) frequency Q in the multilayered cuprates is calculated in the cluster model by the exact diagonalization method. The charge imbalance between the outer CuO 2 plane (OP) with apical oxygen O A and the inner plane (IP) without O A in three-layered Tl 2 Ba 2 Ca 2 Cu 3 O 10 is estimated by comparing our results with the experimental Q . In Tl-based cuprates with more than three layers, we predict a large enhancement of the splitting of Q between OP and IP by taking into account the reduction in bond length between Cu and O A and the resulting increase in charge transfer energy. Our results show that the NQR frequency is a useful quantity for estimating the charge imbalance in the multilayered cuprates. Many studies have been aimed at a high superconducting transition temperature, T c . Regarding high-T c cuprates, maximum T c depends on materials, e.g., T c $ 40 K for the La family and T c $ 90 K for the Y family, even if carrier densities are optimized. In particular, among hole-doped cuprates, such material dependence closely correlates with an energy difference between in-plane and apical oxygens, Á" A .1) Actually, a spatial variation in pairing gap due to a modulation of the apical oxygen O A is observed by scanning tunneling microscopy.2,3) In addition, it is known that the disorder around the apical site is much more harmful on T c than other randomness. 4)On the other hand, the T c of multilayered cuprates correlates with the number of CuO 2 planes in a unit cell, n, and shows a maximum at n ¼ 3.5,6) One of the reasons why T c is suppressed for n > 3 is charge imbalance, [7][8][9][10][11][12] i.e., the hole concentration in pyramidally coordinated outer planes (OPs) is different from that in square-coordinated inner planes (IPs). 5,[7][8][9][10][11][12][13][14] A nuclear magnetic resonance (NMR) study has revealed that the hole concentration in OP, OP , is larger than that in IP, IP .8) The magnitude of charge imbalance, Á ¼ OP À IP , increases with n and becomes 0.10 at most for n ¼ 3.8) Such charge imbalance induces some interesting phases, e.g., two kinds of superconducting gap 7) and the coexistence of superconducting and antiferromagnetic states. [9][10][11][12]15,16) To estimate the local charge density, the nuclear quadrupole resonance (NQR) frequency Q is a useful quantity, 17,18) since Q is determined by a local charge distribution in the ground state. In the NQR measurement for three-layered Tl 2 Ba 2 Ca 2 Cu 3 O 10 (Tl2223), 18) charge imbalance has been observed as two separated peaks with an approximately 6.6 MHz difference. Here, we note that the Knight shift K c is also proportional to a local charge density on a measured site. However, one needs to examine not only the ground state but also the excited states and the neighboring spinspin interactions, since K c is proportional to the susceptibility and the transferred hyperfine couplings. 19) In addition, one needs to measure not only the 63 Cu site but also the 17 O site to estimate the hole densi...

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Anomalous Reflectivity Oscillation of Layered Manganite La_0.5Sr_1.5MnO₄

Cited by 3 publications

References 10 publications

Origin of Periodic Modulations in the Transient Reflectivity Signal at Cryogenic Temperatures

Origin of Periodic Modulations in the Transient Reflectivity Signal at Cryogenic Temperatures

Modulations in Low-Temperature Transient Reflectivity Measurements

Nuclear Quadrupole Resonance Frequency in Multilayered Cuprates

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