Coherent phonons in pyrochlore titanates A2Ti2O7 (A= Dy, Gd, Tb): a phase transition in Dy2Ti2O7 at 110 K

Kamaraju, N. ; Kumar, Sunil ; Saha, Surajit ; Singh, Surjeet ; Suryanarayanan, R. ; Revcolevschi, A. ; Sood, A. K. (2011) Coherent phonons in pyrochlore titanates A2Ti2O7 (A= Dy, Gd, Tb): a phase transition in Dy2Ti2O7 at 110 K Physical Review B: Condensed Matter and Materials Physics, 83 (13). 134104 _1-134104 _6. ISSN 1098-0121

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Official URL: http://prb.aps.org/abstract/PRB/v83/i13/e134104

Related URL: http://dx.doi.org/10.1103/PhysRevB.83.134104

Abstract

We study the generation of coherent optical phonons in spin-frustrated pyrochlore single crystals Dy2Ti2O7, Gd2Ti2O7, and Tb2Ti2O7 using femtosecond laser pulses (65 fs, 1.57 eV) in degenerate time-resolved transmission experiments as a function of temperature from 4 to 296 K. At 4 K, two coherent phonons are observed at ~5.3 THz (5.0 THz) and ~9.3 THz (9.4 THz) for Dy2Ti2O7 (Gd2Ti2O7), whereas three coherent phonons are generated at ~5.0, 8.6, and 9.7 THz for Tb2Ti2O7. In the case of spin-ice Dy2Ti2O7, a clear discontinuity is observed in the linewidths of both the coherent phonons as well as in the phase of lower-energy coherent phonon mode, indicating a subtle structural change at 110 K. Another important observation is a phase difference of π between the modes in all the samples, thus suggesting that the driving forces behind the generation of these modes could be different in nature, unlike a purely impulsive or displacive mechanism.

Item Type:Article
Source:Copyright of this article belongs to American Physical Society.
ID Code:50231
Deposited On:22 Jul 2011 14:03
Last Modified:22 Jul 2011 14:03

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