Spinon confinement and a sharp longitudinal mode in Yb2Pt2Pb in magnetic fields

W J Gannon; I A Zaliznyak; L S Wu; A E Feiguin; A M Tsvelik; F Demmel; Y Qiu; J R D Copley; M S Kim; M C Aronson

doi:10.1038/s41467-019-08715-y

Spinon confinement and a sharp longitudinal mode in Yb₂Pt₂Pb in magnetic fields

Nat Commun. 2019 Mar 8;10(1):1123. doi: 10.1038/s41467-019-08715-y.

Authors

W J Gannon^{1

2}, I A Zaliznyak³, L S Wu^{4

5}, A E Feiguin⁶, A M Tsvelik³, F Demmel⁷, Y Qiu⁸, J R D Copley⁸, M S Kim⁹, M C Aronson^{10

11}

Affiliations

¹ Department of Physics and Astronomy, Texas A&M University, College Station, TX, 77843, USA. william.gannon@ubc.ca.
² Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada. william.gannon@ubc.ca.
³ Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA.
⁴ Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA.
⁵ Department of Physics, South University of Science and Technology of China, 518055, Shenzhen, China.
⁶ Department of Physics, Northeastern University, Boston, MA, 02115, USA.
⁷ ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QZ, UK.
⁸ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
⁹ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA.
¹⁰ Department of Physics and Astronomy, Texas A&M University, College Station, TX, 77843, USA.
¹¹ Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.

Abstract

The fundamental excitations in an antiferromagnetic chain of spins-1/2 are spinons, de-confined fractional quasiparticles that when combined in pairs, form a triplet excitation continuum. In an Ising-like spin chain the continuum is gapped and the ground state is Néel ordered. Here, we report high resolution neutron scattering experiments, which reveal how a magnetic field closes this gap and drives the spin chains in Yb₂Pt₂Pb to a critical, disordered Luttinger-liquid state. In Yb₂Pt₂Pb the effective spins-1/2 describe the dynamics of large, Ising-like Yb magnetic moments, ensuring that the measured excitations are exclusively longitudinal, which we find to be well described by time-dependent density matrix renormalization group calculations. The inter-chain coupling leads to the confinement of spinons, a condensed matter analog of quark confinement in quantum chromodynamics. Insensitive to transverse fluctuations, our measurements show how a gapless, dispersive longitudinal mode arises from confinement and evolves with magnetic order.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't