Origin of the Spin-Orbital Liquid State in a Nearly $J=0$ Iridate ${\mathrm{Ba}}_{3}{\mathrm{ZnIr}}_{2}{\mathrm{O}}_{9}$

Origin of the Spin-Orbital Liquid State in a Nearly $J = 0$ Iridate ${Ba}_{3} {ZnIr}_{2} O_{9}$

Abhishek Nag, S. Middey, Sayantika Bhowal, S. K. Panda, Roland Mathieu, J. C. Orain, F. Bert, P. Mendels, P. G. Freeman, M. Mansson, H. M. Ronnow, M. Telling, P. K. Biswas, D. Sheptyakov, S. D. Kaushik, Vasudeva Siruguri, Carlo Meneghini, D. D. Sarma, Indra Dasgupta, and Sugata Ray

Phys. Rev. Lett. 116, 097205 – Published 3 March 2016

Abstract

We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of ${Ba}_{3} {ZnIr}_{2} O_{9}$ is a realization of a novel spin-orbital liquid state. Our results reveal that ${Ba}_{3} {ZnIr}_{2} O_{9}$ with ${Ir}^{5 +}$ ( $5 d^{4}$ ) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive $J = 0$ state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural ${Ir}_{2} O_{9}$ dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK.

Received 16 July 2015

DOI:https://doi.org/10.1103/PhysRevLett.116.097205

Physics Subject Headings (PhySH)

Spin-orbit coupling

Iridates Transition metal alloys

Density functional theory GGA

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Abhishek Nag¹, S. Middey^2,‡, Sayantika Bhowal³, S. K. Panda^2,§, Roland Mathieu⁴, J. C. Orain⁵, F. Bert⁵, P. Mendels⁵, P. G. Freeman^6,7, M. Mansson^6,8, H. M. Ronnow⁶, M. Telling⁹, P. K. Biswas¹⁰, D. Sheptyakov¹¹, S. D. Kaushik¹², Vasudeva Siruguri¹², Carlo Meneghini¹³, D. D. Sarma¹⁴, Indra Dasgupta^2,3,*, and Sugata Ray^1,2,,†

¹Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
²Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
³Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
⁴Department of Engineering Sciences, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
⁵Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, 91405 Orsay, France
⁶Laboratory for Quantum Magnetism (LQM), École Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland
⁷Jeremiah Horrocks Institute for Mathematics, Physics and Astrophysics, University of Central Lancashire, Preston PR1 2HE, United Kingdom
⁸Department of Materials and Nanophysics, KTH Royal Institute of Technology, Electrum 229, SE-16440 Kista, Sweden
⁹ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX110QX, United Kingdom
¹⁰Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
¹¹Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
¹²UGC-DAE-Consortium for Scientific Research Mumbai Centre, R5 Shed, Bhabha Atomic Research Centre, Mumbai 400085, India
¹³Dipartimento di Scienze, Universitá Roma Tre, Via della Vasca Navale, 84 I-00146 Roma, Italy
¹⁴Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India

^*sspid@iacs.res.in
^,†mssr@iacs.res.in
^‡Present address: Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.
^§Present address: Uppsala University, Uppsala, Sweden.

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Vol. 116, Iss. 9 — 4 March 2016

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Physical Review Letters

Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba3ZnIr2O9

Abhishek Nag, S. Middey, Sayantika Bhowal, S. K. Panda, Roland Mathieu, J. C. Orain, F. Bert, P. Mendels, P. G. Freeman, M. Mansson, H. M. Ronnow, M. Telling, P. K. Biswas, D. Sheptyakov, S. D. Kaushik, Vasudeva Siruguri, Carlo Meneghini, D. D. Sarma, Indra Dasgupta, and Sugata Ray

Phys. Rev. Lett. 116, 097205 – Published 3 March 2016

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Origin of the Spin-Orbital Liquid State in a Nearly $J = 0$ Iridate ${Ba}_{3} {ZnIr}_{2} O_{9}$