Pressure-tuning of the electron-phonon coupling: the insulator to metal transition in manganites

Abstract

A comprehensive understanding of the physical origin of the unique magnetic and transport properties of A_(1-x)A'^xMnO_3 manganites (A = trivalent rare-earth and A' = divalent alkali-earth metal) is still far from being achieved. The complexity of these systems arises from the interplay among several competing interactions of comparable strength. Recently the electron-phonon coupling, triggered by a Jahn-Teller distortion of the MnO_6 octahedra, has been recognised to play an essential role in the insulator to metal transition and in the closely related colossal magneto-resistance. The pressure tuning of the octahedral distortion gives a unique possibility to separate the basic interactions and, at least in principle, to follow the progressive transformation of a manganite from an intermediate towards a weak electron-phonon coupling regime. Using a diamond anvil cell, temperature and pressure-dependent infrared absorption spectra of La_(0.75)Ca_(0.25)MnO_3 have been collected and, from the spectral weight analysis, the pressure dependence of the insulator to metal transition temperature T_IM has been determined for the first time up to 11.2 GPa. The T_IM(P) curve we proposed to model the present data revealed a universality character in accounting for the whole class of intermediate coupling compounds. This property can be exploited to distinguish the intermediate from the weak coupling compounds pointing out the fundamental differences between the two coupling regimes.

8 pages, 4 figures

References in corpus (5)

• Double Exchange Alone Does Not Explain the Resistivity of $L{a}_{1-x}S{r}_{x}Mn{O}_3$
• On the Fermi Liquid to Polaron Crossover II: Double Exchange and the Physics of "Colossal" Magnetoresistance
• Optical Conductivity of Manganites: Crossover from Jahn-Teller Small Polaron to Coherent Transport in the Ferromagnetic State
• Polaron Absorption in a Perovskite Manganite La0.7Ca0.3MnO3
• Optical spectral weights and the ferromagnetic transition temperature of CMR manganites: relevance of double-exchange to real materials

Cited by in corpus (11)

• Polaron Crossover and Bipolaronic Metal-Insulator Transition in the Holstein model at half-filling
• Long Range Coulomb Interactions and Nanoscale Electronic Inhomogeneities in Correlated Oxides
• Pressure induced magnetic phase separation in La${}_{0.75}$Ca${}_{0.25}$MnO${}_3$ manganite
• Effect of pressure on the polarized infrared optical response of quasi-one-dimensional LaTiO${}_{3.41}$
• High-Pressure Phase Diagram in the Manganites: a Two-site Model Study
• Infrared study of the pressure-induced isostructural metallic transition in Mo${}_{0:5}$W${}_{0:5}$S${}_2$
• High pressure Raman study of La${}_{1-x}$Ca${}_x$MnO${}_{3-\delta }$ manganites
• Structural Disorder Induced Polaron Formation and Magnetic Scattering in the Disordered Holstein-Double Exchange Model
• Density matrix of electrons coupled to phonons and the electron-phonon entanglement content of excited states
• A phenomenological model for the pressure sensitivity of the Curie temperature in hole-doped manganites
• Scaling behavior of Charge order melting in Magnetic field-Pressure-Temperature space of 2.5% Al doped Pr${}_{0.5}$Ca${}_{0.5}$MnO${}_3$