Clues and criteria for designing a Kitaev spin liquid revealed by thermal and spin excitations of the honeycomb iridate Na2IrO3

Youhei Yamaji, Takafumi Suzuki, Takuto Yamada, Sei Ichiro Suga, Naoki Kawashima, Masatoshi Imada

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Contrary to the original expectation, Na2IrO3 is not a Kitaev's quantum spin liquid (QSL) but shows a zigzag-type antiferromagnetic order in experiments. Here, we propose experimental clues and criteria to measure how a material in hand is close to the Kitaev's QSL state. For this purpose, we systematically study thermal and spin excitations of a generalized Kitaev-Heisenberg model studied by Chaloupka, Phys. Rev. Lett. 110, 097204 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.097204 and an effective ab initio Hamiltonian for Na2IrO3 proposed by Yamaji, Phys. Rev. Lett. 113, 107201 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.107201, by employing a numerical diagonalization method. We reveal that closeness to the Kitaev's QSL is characterized by the following properties, besides trivial criteria such as reduction of magnetic ordered moments and Néel temperatures. (1) Two peaks in the temperature dependence of specific heat at T and Th caused by the fractionalization of spin to two types of Majorana fermions. (2) In between the double peak, a prominent plateau or shoulder pinned at R2ln2 in the temperature dependence of entropy, where R is the gas constant. (3) Failure of the linear spin wave approximation at the low-lying excitations of dynamical structure factors. (4) Small ratio T/Th close to or less than 0.03. According to the proposed criteria, Na2IrO3 is categorized to a compound close to the Kitaev's QSL, and is proven to be a promising candidate for the realization of the QSL if the relevant material parameters can further be tuned by making thin film of Na2IrO3 on various substrates or applying axial pressure perpendicular to the honeycomb networks of iridium ions. Applications of these characterization to (Na1-xLix)2IrO3 and other related materials are also discussed.

Original languageEnglish
Article number174425
JournalPhysical Review B
Volume93
Issue number17
DOIs
Publication statusPublished - 2016 May 24
Externally publishedYes

Fingerprint

Liquids
liquids
excitation
Hamiltonians
Iridium
Spin waves
Fermions
Magnetic moments
Temperature
Specific heat
temperature dependence
Numerical methods
Entropy
Gases
shoulders
Hot Temperature
iridium
Ions
magnons
Thin films

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Clues and criteria for designing a Kitaev spin liquid revealed by thermal and spin excitations of the honeycomb iridate Na2IrO3. / Yamaji, Youhei; Suzuki, Takafumi; Yamada, Takuto; Suga, Sei Ichiro; Kawashima, Naoki; Imada, Masatoshi.

In: Physical Review B, Vol. 93, No. 17, 174425, 24.05.2016.

Research output: Contribution to journalArticle

Yamaji, Youhei ; Suzuki, Takafumi ; Yamada, Takuto ; Suga, Sei Ichiro ; Kawashima, Naoki ; Imada, Masatoshi. / Clues and criteria for designing a Kitaev spin liquid revealed by thermal and spin excitations of the honeycomb iridate Na2IrO3. In: Physical Review B. 2016 ; Vol. 93, No. 17.
@article{0af0ac40b6264ac5a06fcaf8cacd6b8f,
title = "Clues and criteria for designing a Kitaev spin liquid revealed by thermal and spin excitations of the honeycomb iridate Na2IrO3",
abstract = "Contrary to the original expectation, Na2IrO3 is not a Kitaev's quantum spin liquid (QSL) but shows a zigzag-type antiferromagnetic order in experiments. Here, we propose experimental clues and criteria to measure how a material in hand is close to the Kitaev's QSL state. For this purpose, we systematically study thermal and spin excitations of a generalized Kitaev-Heisenberg model studied by Chaloupka, Phys. Rev. Lett. 110, 097204 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.097204 and an effective ab initio Hamiltonian for Na2IrO3 proposed by Yamaji, Phys. Rev. Lett. 113, 107201 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.107201, by employing a numerical diagonalization method. We reveal that closeness to the Kitaev's QSL is characterized by the following properties, besides trivial criteria such as reduction of magnetic ordered moments and N{\'e}el temperatures. (1) Two peaks in the temperature dependence of specific heat at T and Th caused by the fractionalization of spin to two types of Majorana fermions. (2) In between the double peak, a prominent plateau or shoulder pinned at R2ln2 in the temperature dependence of entropy, where R is the gas constant. (3) Failure of the linear spin wave approximation at the low-lying excitations of dynamical structure factors. (4) Small ratio T/Th close to or less than 0.03. According to the proposed criteria, Na2IrO3 is categorized to a compound close to the Kitaev's QSL, and is proven to be a promising candidate for the realization of the QSL if the relevant material parameters can further be tuned by making thin film of Na2IrO3 on various substrates or applying axial pressure perpendicular to the honeycomb networks of iridium ions. Applications of these characterization to (Na1-xLix)2IrO3 and other related materials are also discussed.",
author = "Youhei Yamaji and Takafumi Suzuki and Takuto Yamada and Suga, {Sei Ichiro} and Naoki Kawashima and Masatoshi Imada",
year = "2016",
month = "5",
day = "24",
doi = "10.1103/PhysRevB.93.174425",
language = "English",
volume = "93",
journal = "Physical Review B-Condensed Matter",
issn = "2469-9950",
publisher = "American Physical Society",
number = "17",

}

TY - JOUR

T1 - Clues and criteria for designing a Kitaev spin liquid revealed by thermal and spin excitations of the honeycomb iridate Na2IrO3

AU - Yamaji, Youhei

AU - Suzuki, Takafumi

AU - Yamada, Takuto

AU - Suga, Sei Ichiro

AU - Kawashima, Naoki

AU - Imada, Masatoshi

PY - 2016/5/24

Y1 - 2016/5/24

N2 - Contrary to the original expectation, Na2IrO3 is not a Kitaev's quantum spin liquid (QSL) but shows a zigzag-type antiferromagnetic order in experiments. Here, we propose experimental clues and criteria to measure how a material in hand is close to the Kitaev's QSL state. For this purpose, we systematically study thermal and spin excitations of a generalized Kitaev-Heisenberg model studied by Chaloupka, Phys. Rev. Lett. 110, 097204 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.097204 and an effective ab initio Hamiltonian for Na2IrO3 proposed by Yamaji, Phys. Rev. Lett. 113, 107201 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.107201, by employing a numerical diagonalization method. We reveal that closeness to the Kitaev's QSL is characterized by the following properties, besides trivial criteria such as reduction of magnetic ordered moments and Néel temperatures. (1) Two peaks in the temperature dependence of specific heat at T and Th caused by the fractionalization of spin to two types of Majorana fermions. (2) In between the double peak, a prominent plateau or shoulder pinned at R2ln2 in the temperature dependence of entropy, where R is the gas constant. (3) Failure of the linear spin wave approximation at the low-lying excitations of dynamical structure factors. (4) Small ratio T/Th close to or less than 0.03. According to the proposed criteria, Na2IrO3 is categorized to a compound close to the Kitaev's QSL, and is proven to be a promising candidate for the realization of the QSL if the relevant material parameters can further be tuned by making thin film of Na2IrO3 on various substrates or applying axial pressure perpendicular to the honeycomb networks of iridium ions. Applications of these characterization to (Na1-xLix)2IrO3 and other related materials are also discussed.

AB - Contrary to the original expectation, Na2IrO3 is not a Kitaev's quantum spin liquid (QSL) but shows a zigzag-type antiferromagnetic order in experiments. Here, we propose experimental clues and criteria to measure how a material in hand is close to the Kitaev's QSL state. For this purpose, we systematically study thermal and spin excitations of a generalized Kitaev-Heisenberg model studied by Chaloupka, Phys. Rev. Lett. 110, 097204 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.097204 and an effective ab initio Hamiltonian for Na2IrO3 proposed by Yamaji, Phys. Rev. Lett. 113, 107201 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.107201, by employing a numerical diagonalization method. We reveal that closeness to the Kitaev's QSL is characterized by the following properties, besides trivial criteria such as reduction of magnetic ordered moments and Néel temperatures. (1) Two peaks in the temperature dependence of specific heat at T and Th caused by the fractionalization of spin to two types of Majorana fermions. (2) In between the double peak, a prominent plateau or shoulder pinned at R2ln2 in the temperature dependence of entropy, where R is the gas constant. (3) Failure of the linear spin wave approximation at the low-lying excitations of dynamical structure factors. (4) Small ratio T/Th close to or less than 0.03. According to the proposed criteria, Na2IrO3 is categorized to a compound close to the Kitaev's QSL, and is proven to be a promising candidate for the realization of the QSL if the relevant material parameters can further be tuned by making thin film of Na2IrO3 on various substrates or applying axial pressure perpendicular to the honeycomb networks of iridium ions. Applications of these characterization to (Na1-xLix)2IrO3 and other related materials are also discussed.

UR - http://www.scopus.com/inward/record.url?scp=84971009167&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84971009167&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.93.174425

DO - 10.1103/PhysRevB.93.174425

M3 - Article

AN - SCOPUS:84971009167

VL - 93

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 2469-9950

IS - 17

M1 - 174425

ER -