Clear Experimental Signature of Charge-Orbital density wave in Nd$_{1-x}$Ca$_{1+x}$MnO$_{4}$

TL;DR

This study provides direct heat capacity evidence for charge-orbital density wave transitions in Nd$_{1-x}$Ca$_{1+x}$MnO$_{4}$, confirming earlier microscopy findings and highlighting strong electron-phonon interactions.

Contribution

It presents the first direct heat capacity measurements confirming charge-orbital ordering in Nd$_{1-x}$Ca$_{1+x}$MnO$_{4}$, supporting previous microscopy evidence.

Findings

Two main transitions at 310-314 K and 143 K

Evidence of strong electron-phonon coupling

Confirmation of charge-orbital density wave presence

Abstract

Single Crystals of Nd$_{1-x}$Ca$_{1+x}$MnO$_{4}$ have been prepared by the travelling floating-zone method, and possible evidence of a charge -orbital density wave in this material presented earlier [PRB68,092405 (2003)] using High Resolution Electron Microscopy [HRTEM] and Electron Diffraction [ED]. In the current note we present direct evidence of charge-orbital ordering in this material using heat capacity measurements. Our heat capacity measurements indicate a clear transition consistent with prior observation. We find two main transitions, one at temperature $T_{_H}=310-314$ K, and other at $T_{_A}=143$ K. In addition, we may also conclude that there is a strong electron-phonon coupling in this material.