Anomalous critical behavior near the quantum critical point of a hole-doped La2CuO4

TL;DR

This study investigates quantum critical behavior in hole-doped La2CuO4, revealing anomalous critical exponents and scaling functions near the quantum critical point, challenging existing theories and confirming the quantum crossover phase boundary.

Contribution

First experimental observation of the quantum crossover phase boundary and anomalous critical behavior in hole-doped La2CuO4 near its quantum critical point.

Findings

Observed quantum crossover phase boundary in La2CuO4

Detected anomalous critical exponents near the quantum critical point

Challenged current theories with unexpected scaling behavior

Abstract

The Landau-Ginzburg-Wilson paradigm for critical phenomena is spectacularly successful whenever the critical temperature is finite and all fluctuation modes, with characteristic energies much smaller than the thermal energy, obey classical statistics. In zero-temperature quantum critical phenomena, classical thermal fluctuations are replaced by zero-point quantum fluctuations and quantum-mechanical generalization of the Landau-Ginzburg-Wilson paradigm has been a central topic in condensed-matter physics. In this neutron-scattering study on spin fluctuations near the quantum critical point induced by hole-doping in La2CuO4 (Li doping concentration from 0.04 to 0.1), the phase boundary for quantum crossover expected from the generalized quantum theory for critical phenomena was observed for the first time. Furthermore, critical exponent and scaling function become anomalous near the quantum critical point, which has not been expected in current theories.