TY - JOUR
T1 - Quantum criticality associated with dimensional crossover in the iso-electronic series Ca_{2-x}Sr_{x}RuO_{4}
AU - Acharya, Swagata
AU - Dey, Dibyendu
AU - Maitra, Tulika
AU - Taraphder, Arghya
PY - 2018/6/21
Y1 - 2018/6/21
N2 - The iso-electronic series, Ca$_{2-x}$Sr$_{x}$RuO$_{4}$, is studied within the GGA (and spin-orbit coupled GGA) plus DMFT formalism using the hybridization expansion of continuous time Quantum Monte Carlo impurity solver. While GGA+DMFT provides insights into the dynamics of the excited states for this series, GGA+U and energy considerations provide a complementary understanding of the ground state structural and electronic properties. While the dynamical correlations make Sr$_{2}$RuO$_{4}$ a Hund's metal, they drive Ca$_{2}$RuO$_{4}$ to a Mott insulating ground state. We study the single-particle and two-particle responses at three different points ($x = 2.0, 0.5, 0.0$) to understand the anomalous cross-over from Hund's metal ($x = 2.0 $) to a Mott insulator ($x = 0 $) and observe that a structural distortion is likely to be responsible. Further, dynamical correlations reveal that the band-width ($W$) of the Hund's metal is larger than its effective local Hubbard $U$, and a finite Hund's coupling $J_{H}$ helps it remain in a bad metallic and nearly spin-frozen state over a large temperature range. Ca$_{2}$RuO$_{4}$, though, is driven to the proximity of a Mott transition by the narrowing of band width ($U/W > 1.5$). We show that there is a critical end point of second-order structural transition at $x = 0.5$, where spin fluctuations become critical and follow the scaling of local quantum criticality. We argue that this critical end point of quasi-$3D$ nature is associated with an effective dimensional cross-over from the quasi-$2D$ structures of $x = 2.0$ and $x=0.0$ end-members. Finally we draw an electronic and magnetic phase diagram in $T$-$x$ plane with these novel inputs, with a fan like region starting from the quantum critical end point at $x = 0.5.$
AB - The iso-electronic series, Ca$_{2-x}$Sr$_{x}$RuO$_{4}$, is studied within the GGA (and spin-orbit coupled GGA) plus DMFT formalism using the hybridization expansion of continuous time Quantum Monte Carlo impurity solver. While GGA+DMFT provides insights into the dynamics of the excited states for this series, GGA+U and energy considerations provide a complementary understanding of the ground state structural and electronic properties. While the dynamical correlations make Sr$_{2}$RuO$_{4}$ a Hund's metal, they drive Ca$_{2}$RuO$_{4}$ to a Mott insulating ground state. We study the single-particle and two-particle responses at three different points ($x = 2.0, 0.5, 0.0$) to understand the anomalous cross-over from Hund's metal ($x = 2.0 $) to a Mott insulator ($x = 0 $) and observe that a structural distortion is likely to be responsible. Further, dynamical correlations reveal that the band-width ($W$) of the Hund's metal is larger than its effective local Hubbard $U$, and a finite Hund's coupling $J_{H}$ helps it remain in a bad metallic and nearly spin-frozen state over a large temperature range. Ca$_{2}$RuO$_{4}$, though, is driven to the proximity of a Mott transition by the narrowing of band width ($U/W > 1.5$). We show that there is a critical end point of second-order structural transition at $x = 0.5$, where spin fluctuations become critical and follow the scaling of local quantum criticality. We argue that this critical end point of quasi-$3D$ nature is associated with an effective dimensional cross-over from the quasi-$2D$ structures of $x = 2.0$ and $x=0.0$ end-members. Finally we draw an electronic and magnetic phase diagram in $T$-$x$ plane with these novel inputs, with a fan like region starting from the quantum critical end point at $x = 0.5.$
U2 - 10.1088/2399-6528/aace29
DO - 10.1088/2399-6528/aace29
M3 - Article
JO - Journal of Physics Communications
JF - Journal of Physics Communications
ER -