Spin waves and quantum criticality in the frustrated XY pyrochlore antiferromagnet Er2Ti2O7.
We report detailed measurements of the low temperature magnetic phase diagram of Er2Ti2O7. Heat capacity and time-of-flight neutron scattering studies of single crystals reveal unconventional low-energy states. Er3+ magnetic ions reside on a pyrochlore lattice in Er2Ti2O7, where local XY anisotropy and antiferromagnetic interactions give rise to a unique frustrated system. In zero field, the ground state exhibits coexisting short and long-range order, accompanied by soft collective spin excitations previously believed to be absent. The application of finite magnetic fields tunes the ground state continuously through a landscape of noncollinear phases, divided by a zero temperature phase transition at micro{0}H{c} approximately 1.5 T. The characteristic energy scale for spin fluctuations is seen to vanish at the critical point, as expected for a second order quantum phase transition driven by quantum fluctuations.
Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada.
J P C
JP
Ruff
J P
JP
Clancy
A
A
Bourque
M A
MA
White
M
M
Ramazanoglu
J S
JS
Gardner
Y
Y
Qiu
J R D
JR
Copley
M B
MB
Johnson
H A
HA
Dabkowska
B D
BD
Gaulin