Low frequency spin dynamics in XY quantum spin ice Yb$_2$Pt$_2$O$_7$

TL;DR

This study investigates the low frequency spin dynamics in Yb$_2$Pt$_2$O$_7$, revealing a field-dependent magnon gap and emergent low energy excitations through NMR and specific heat measurements.

Contribution

It provides new insights into the magnetic excitations and spin dynamics in Yb$_2$Pt$_2$O$_7$, a material similar to quantum spin ice, using $^{195}$Pt NMR techniques.

Findings

Magnon gap decreases linearly with magnetic field.

Emergence of low energy spin excitations below 0.5 T.

Field-induced changes in spin dynamics observed.

Abstract

The XY pyrochlore Yb$_2$Ti$_2$O$_7$, with pseudo spin 1/2 at the Yb$^{3+}$ site, has been celebrated as potential host for the quantum spin ice state. The substitution of non-magnetic Ti with Pt gives Yb$_2$Pt$_2$O$_7$, a system with remarkably similar magnetic properties. The large nuclear gyromagnetic ratio ($\gamma_{n}/2 \pi = 9.15$~MHz/T) of $^{195}$Pt makes Yb$_2$Pt$_2$O$_7$ an ideal material for NMR investigation of its unconventional magnetic properties. Based on the $^{195}$Pt nuclear spin-lattice relaxation rate $1/T_1$ and the magnetic specific heat $C_{p}$ measured in a broad range of magnetic field $B_{ext}$, we demonstrate that the field-induced magnon gap linearly decreases with $B_{ext}$ but additional low energy mode of spin excitations emerge below $\sim 0.5$~T.