Optical evidence of quantum rotor orbital excitations in orthorhombic manganites

Journal Article · Sun May 15 00:00:00 EDT 2016 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776116050174· OSTI ID:22617276

Kugel, K. I. ^[1]; Potůček, Z. ^[2]; Kusmartseva, O. E. ^[1]; Goryachev, N. S. ^[3]; Bryknar, Z. ^[2]; Demikhov, E. I. ^[4]; Trepakov, V. A.; Dejneka, A. ^[5]; Kusmartsev, F. V. ^[1]; Stoneham, A. M. ^[6]

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1. Loughborough University, Department of Physics (United Kingdom)
2. Czech Technical University (Czech Republic)
3. Russian Academy of Sciences, Institute of Problems in Chemical Physics (Russian Federation)
4. Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
5. Academy of Sciences of the Czech Republic, Institute of Physics (Czech Republic)
6. University College London, London Centre for Nanotechnology (United Kingdom)

In magnetic compounds with Jahn–Teller (JT) ions (such as Mn{sup 3+} or Cu{sup 2+}), the ordering of the electron or hole orbitals is associated with cooperative lattice distortions. There the role of JT effect, although widely recognized, is still elusive in the ground state properties. Here we discovered that, in these materials, there exist excitations whose energy spectrum is described in terms of the total angular momentum eigenstates and is quantized as in quantum rotors found in JT centers. We observed features originating from these excitations in the optical spectra of a model compound LaMnO{sub 3} using ellipsometry technique. They appear clearly as narrow sidebands accompanying the electron transition between the JT split orbitals at neighboring Mn{sup 3+} ions, displaying anomalous temperature behavior around the Néel temperature T{sub N} ≈ 140 K. We present these results together with new experimental data on photoluminescence found in LaMnO{sub 3}, which lend additional support to the ellipsometry implying the electronic-vibrational origin of the quantum rotor orbital excitations. We note that the discovered orbital excitations of quantum rotors may play an important role in many unusual properties observed in these materials upon doping, such as high-temperature superconductivity and colossal magnetoresistance.

• OSTI ID: 22617276
• Journal Information: Journal of Experimental and Theoretical Physics, Vol. 122, Issue 5; Other Information: Copyright (c) 2016 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANGULAR MOMENTUM
COPPER IONS
EIGENSTATES
ELLIPSOMETRY
ENERGY SPECTRA
EXCITATION
GROUND STATES
JAHN-TELLER EFFECT
LANTHANUM COMPOUNDS
MAGNETIC MATERIALS
MAGNETORESISTANCE
MANGANATES
MANGANESE IONS
ORTHORHOMBIC LATTICES
PHOTOLUMINESCENCE
SUPERCONDUCTIVITY