A low-dimensional spin S = 1/2 system at the quantum critical limit: Na2V2O7

TL;DR

Na2V2O7 is a low-dimensional spin-1/2 system that exhibits a quantum critical point at zero magnetic field, with magnetic moments being quenched below 100 K and a phase transition occurring at very low temperatures.

Contribution

This study provides experimental evidence of quantum critical behavior in Na2V2O7 through susceptibility and NMR measurements, highlighting its potential as a model for quantum phase transitions.

Findings

V^{4+} moments are quenched below 100 K

A phase transition occurs at very low temperatures

Critical temperature shifts towards zero with decreasing magnetic field

Abstract

We report the results of measurements of the dc-susceptibility and the 23Na-NMR response of Na2V2O7, a recently synthesized, non metallic low dimensional spin system. Our results indicate that upon reducing the temperature to below 100 K, the V^{4+} moments are gradually quenched, leaving only one moment out of 9 active. The NMR data reveal a phase transition at very low temperatures. With decreasing applied field H, the critical temperature shifts towards T = 0 K, suggesting that Na2V2O7 may be regarded as an insulator reaching a quantum critical point at H = 0.