Quantum and classical criticality in a dimerized quantum antiferromagnet

Merchant, P.; Normand, B.; Krämer, Karl; Boehm, M.; McMorrow, D. F.; Rüegg, Ch. (2014). Quantum and classical criticality in a dimerized quantum antiferromagnet. Nature physics, 10(5), pp. 373-379. Nature Publishing Group 10.1038/nphys2902

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A quantum critical point (QCP) is a singularity in the phase diagram arising because of quantum mechanical fluctuations. The exotic properties of some of the most enigmatic physical systems, including unconventional metals and superconductors, quantum magnets and ultracold atomic condensates, have been related to the importance of critical quantum and thermal fluctuations near such a point. However, direct and continuous control of these fluctuations has been difficult to realize, and complete thermodynamic and spectroscopic information is required to disentangle the effects of quantum and classical physics around a QCP. Here we achieve this control in a high-pressure, high-resolution neutron scattering experiment on the quantum dimer material TlCuCl3. By measuring the magnetic excitation spectrum across the entire quantum critical phase diagram, we illustrate the similarities between quantum and thermal melting of magnetic order. We prove the critical nature of the unconventional longitudinal (Higgs) mode of the ordered phase by damping it thermally. We demonstrate the development of two types of criticality, quantum and classical, and use their static and dynamic scaling properties to conclude that quantum and thermal fluctuations can behave largely independently near a QCP.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Krämer, Karl

Subjects:

500 Science > 540 Chemistry

ISSN:

1745-2473

Publisher:

Nature Publishing Group

Language:

English

Submitter:

Karl Krämer

Date Deposited:

03 Nov 2014 11:19

Last Modified:

12 Jan 2016 16:49

Publisher DOI:

10.1038/nphys2902

ArXiv ID:

1405.2391

BORIS DOI:

10.7892/boris.59692

URI:

https://boris.unibe.ch/id/eprint/59692

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