Charge-spin coupling as a probe of correlated quantum materials Joo - - PowerPoint PPT Presentation

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Charge-spin coupling as a probe of correlated quantum materials Joo - - PowerPoint PPT Presentation

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Charge-spin coupling as a probe of correlated quantum materials Joo N. B. Rodrigues PI: Lucas K. Wagner Department of Physics University of Illinois at Urbana-Champaign 4 th June 2019 Acknowledgments: Center for Emergent Superconductivity,

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Charge-spin coupling as a probe of correlated quantum materials

João N. B. Rodrigues PI: Lucas K. Wagner

Department of Physics University of Illinois at Urbana-Champaign

4th June 2019

Acknowledgments: Center for Emergent Superconductivity, funded by Department of Energy award DEAC0298CH1088. Computational resources of University of Illinois Campus Cluster and Blue Waters funded by awards OCI-0725070 and ACI-1238993.

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Quantum materials are all about collective behavior

1023 interacting particles (electrons and nuclei) with position and spin

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Collective behavior determines materials’ properties

Insulator Metal

Electric conduction Magnetic ordering

Antiferromagnet Ferromagnet Paramagnet

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Collective behavior determines materials’ properties

Insulator Metal

Electric conduction Magnetic ordering

Antiferromagnet Ferromagnet Paramagnet

High temperature superconductivity Unconventional magnetic orders

Adapted from extremetech.com Adapted from asianscientist.com

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Some of the materials with such unusual properties seem to have a strong coupling between magnetic and orbital degrees of freedom

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Iron-pnictides (FeAs)

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Iron-pnictides (FeAs)

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Iron-pnictides (FeAs)

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Iron-pnictides (FeAs)

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Iron-pnictides (FeAs)

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Iron-pnictides (FeAs) Superconducting pairing mediated by charge-spin interactions?

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Iron-pnictides (FeAs) Superconducting pairing mediated by charge-spin interactions?

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We are looking for more materials that have this kind of coupling between charge and spin degrees of freedom Is there a cheap way of estimating this coupling in a material?

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A cheap way of estimating charge-spin coupling

Density Functional Theory (DFT) to calculate charge and spin densities.

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A cheap way of estimating charge-spin coupling

Density Functional Theory (DFT) to calculate charge and spin densities.

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A cheap way of estimating charge-spin coupling

Charge-spin susceptibility, χ, as an estimator of charge-spin coupling: χ = ∆ρ ∆s =

  • dr |ρ(r) − ρ0(r)|
  • dr |s(r) − s0(r)|
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A cheap way of estimating charge-spin coupling

Charge-spin susceptibility, χ, as an estimator of charge-spin coupling: χ = ∆ρ ∆s =

  • dr |ρ(r) − ρ0(r)|
  • dr |s(r) − s0(r)|

Average over magnetic textures: χcs ≡ 1

N

  • i

∆ρi ∆si

with i = , , , , . . .

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Charge-spin response qualitatively different across materials.

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Charge-spin response qualitatively different across materials.

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Charge-spin response qualitatively different across materials. The charge-spin susceptibility χcs gives a sense of how strong is the charge-spin response.

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Can this coupling differentiate materials?

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Can this coupling differentiate materials? Our test set

Cuprates Ba-122 FeX 214s TMDCs MPX3

SrCuO2, CaCuO2, T-La2CuO4, T'-La2CuO4 BaM2As2 with M=Ni,Mn, Fe,Cr,Co,Cu. FeX with X=Se,S,T e La2MO4 (M=Co,Ni), Sr2MO4 (M=V,Cr, Mn,Fe,Co) and K2MF 4 (M=Co,Ni,Cu) MSe2 (M=Ti, Nb,T a,W) and MS2 (M=Mo,T a) VPS3, NiPSe3, CdPSe3, CrGeT e3

Unconventional high-temperature superconductors, strange metals, non-trivial magnetic ground states.

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Can this coupling differentiate materials? Our test set

Cuprates Ba-122 FeX 214s TMDCs MPX3

SrCuO2, CaCuO2, T-La2CuO4, T'-La2CuO4 BaM2As2 with M=Ni,Mn, Fe,Cr,Co,Cu. FeX with X=Se,S,T e La2MO4 (M=Co,Ni), Sr2MO4 (M=V,Cr, Mn,Fe,Co) and K2MF 4 (M=Co,Ni,Cu) MSe2 (M=Ti, Nb,T a,W) and MS2 (M=Mo,T a) VPS3, NiPSe3, CdPSe3, CrGeT e3

Unconventional high-temperature superconductors, strange metals, non-trivial magnetic ground states.

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Can we compute the charge-spin response accurately yet cheaply?

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Can we compute the charge-spin response accurately yet cheaply? Use density functional theory (DFT)

(some quantum Monte Carlo for benchamark) DFT+U functional (which simulates strong electron-electron interactions in transition metal atoms d-orbitals) Multiple DFT+U calculations to control errors. (U = 0, 5 and 10 eV [details in arXiv:1810.03014])

[Cococcioni and Gironcoli PRB 71, 035105 (2005)]

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High-throughput calculations with Blue Waters

Multiple DFT+U

+

Several magnetic orders ≃ 1000 node-hours per material.

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High-throughput calculations with Blue Waters

Multiple DFT+U

+

Several magnetic orders ≃ 1000 node-hours per material. Checking accuracy of charge-spin susceptibility (from DFT+U) with diffusion Monte Carlo on small set of materials (≃ 40000 node-hours per material).

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Materials in our test set according to their charge-spin susc (for U = 5 eV)

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

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Materials in our test set according to their charge-spin susc (for U = 5 eV)

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

CuO and Fe-based?

yes no

High-Tc unconventional superconductors; bad metals; disordered magnetic states;

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Materials in our test set according to their charge-spin susc (for U = 5 eV)

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

CuO and Fe-based?

yes no

High-Tc unconventional superconductors; bad metals; disordered magnetic states; Mott insulator without long-range

  • rder; metallic under pressure;

nearby unconventional metal phase; Disordered magnetic metal; unchanged upon doping and pressure;

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Materials in our test set according to their charge-spin susc (for U = 5 eV)

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

CuO and Fe-based?

yes no

High-Tc unconventional superconductors; bad metals; disordered magnetic states; Metallic ferromagnet at low-T; turns SC with H2O doping (Tc=5K); Mott insulator without long-range

  • rder; metallic under pressure;

nearby unconventional metal phase; Disordered magnetic metal; unchanged upon doping and pressure;

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Materials in our test set according to their charge-spin susc (for U = 5 eV)

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

CuO and Fe-based?

yes no

High-Tc unconventional superconductors; bad metals; disordered magnetic states; AFM semiconductor; pressure induces SM-to-metal + magnetic transition; chemical doping little effect; Metallic ferromagnet at low-T; turns SC with H2O doping (Tc=5K); Mott insulator without long-range

  • rder; metallic under pressure;

nearby unconventional metal phase; Disordered magnetic metal; unchanged upon doping and pressure;

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Materials in our test set according to their charge-spin susc (for U = 5 eV)

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

CuO and Fe-based?

yes no

High-Tc unconventional superconductors; bad metals; disordered magnetic states; AFM semiconductor; pressure induces SM-to-metal + magnetic transition; chemical doping little effect; Metallic ferromagnet at low-T; turns SC with H2O doping (Tc=5K); Mott insulator without long-range

  • rder; metallic under pressure;

nearby unconventional metal phase; Disordered magnetic metal; unchanged upon doping and pressure; Mostly conventional magnets, insulators

  • r metals.
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Accomplishments: Solid evidence that materials with medium-to- large charge-spin coupling generally exhibit un- common correlated phases of matter. Broader impacts: New computational probe of electronic correlations in quantum materials. Accelerate material discovery ⇒ computational- guided searches. Currently looking into a set of scarcely studied materials Charge-spin susceptibility identified some interesting ones Working with experimental group at UIUC which is interested in exploring these materials

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Summary

Materials with large charge- spin coupling generally present uncommon correlated pases.

arXiv:1810.03014

Charge-spin susceptibility is easy to compute. Probes charge-spin coupling.

BaCo2As2 Sr2VO4 T'-La2CuO4 Sr2CoO4

  • -BaFe2As2

t-BaFe2As2 FeTe FeS t-FeSe Sr2FeO4

  • -FeSe

CaCuO2 SrCuO2 T-La2CuO4 TaSe2 K2CoF4 TaS2 Sr2CrO4 NbSe2 BaCr2As2 La2NiO4 BaMn2As2 NiPSe3 La2CoO4 Sr2MnO4 CrGeTe3 K2CuF4 K2NiF4

Material

0.00 0.25 0.50

Charge-spin susceptibility

CuO and Fe-based?

yes no

High-Tc unconventional superconductors; bad metals; disordered magnetic states; AFM semiconductor; pressure induces SM-to-metal + magnetic transition; chemical doping little effect; Metallic ferromagnet at low-T; turns SC with H2O doping (Tc=5K); Mott insulator without long-range

  • rder; metallic under pressure;

nearby unconventional metal phase; Disordered magnetic metal; unchanged upon doping and pressure; Mostly conventional magnets, insulators

  • r metals.

Working with experimental group to explore new materials