Severe Fermi Surface Reconstruction at a Metamagnetic-Transition in Ca$_{2-x}$Sr$_x$RuO$_4$ (for $0.2 \leq x \leq 0.5$)

TL;DR

This study reveals a significant Fermi surface reconstruction at a metamagnetic transition in Ca$_{2-x}$Sr$_x$RuO$_4$, highlighting the complex interplay of electronic states influenced by Ca concentration and magnetic field.

Contribution

It provides experimental evidence and theoretical insights into Fermi surface changes and electronic state coexistence in Ca$_{2-x}$Sr$_x$RuO$_4$ near a metamagnetic transition.

Findings

Sharp decrease in Hall constant at the transition

Change in AMRO structure indicating FS reconstruction

Dependence of FS on Ca concentration

Abstract

We report an electrical transport study in Ca$_{2-x}$Sr$_{x}$RuO$_4$ single crystals at high magnetic fields ($B$). For $x =0.2$, the Hall constant $R_{xy}$ decreases sharply at an anisotropic metamagnetic (MM) transition reaching its value for Sr$_2$RuO$_4$ at high fields. A sharp decrease in the $A$ coefficient of the resistivity $T^2$-term and a change in the structure of the angular magnetoresistance oscillations (AMRO) for $B$ rotating in the planes, confirms the reconstruction of the Fermi surface (FS). Our observations and LDA calculations indicate a strong dependence of the FS on the Ca concentration and suggest the coexistence of itinerant and localized electronic states in single layered ruthenates.