Superconducting, charge or spin density wave, and magnetic order in - - PowerPoint PPT Presentation

Superconducting, charge or spin density wave, and magnetic order in d- and f-electron materials

• M. Brian Maple

University of California, San Diego Conference on Concepts in Electron Correlation, Hvar, Croatia, September, 2008

• Competing interactions in multinary d- and f-electron compounds

can often be readily “tuned” by x, P, H (“knobs”) – Wide variety of correlated electron phenomena – Rich and complex phase diagrams in the hyperspace of T, x, P, H

• Traced to various factors; e.g.,

– Hybridization between localized d- or f-electron states and itinerant electron states – Large unit cells, molecular units, atomic cages, low D, etc. – Coupled charge, spin, orbital, lattice degrees of freedom

• Examples

– Correlated electron phenomena in filled skutterudites (various talks) – Interplay between superconducting, CDW or SDW, and magnetic order in d- and f-electron materials (this talk)

• High pressure and chemical substitution experiments on various materials that

address this latter issue – Systems URu2-xRexSi2 RTe3 High Tc superconducting lanthanide iron oxypnictides

Competing interactions in d- and f-electron materials

Superconductivity, hidden order, and magnetic order in the system URu2-xRexSi2 Coworkers

University of California, San Diego

• N. P. Butch,1 J. R. Jeffries,2 T. A. Sayles,3 B. T. Yukich, D. A. Zocco

1 - U. Maryland 2 - Lawrence Livermore National Laboratory 3 - UCSD Medical School - Radiology

More information – this conference Poster:

Anomalous mixed-state thermal conductivity in URu2Si2

• H. Adachi, M. Sigrist

Talk:

Calculated electronic structure properties of URu2Si2 and Ce-115 materials Peter Oppeneer

• Moderately heavy Fermi liquid (m* ~ 25 me)
• “Hidden order (HO)” phase (T0 ≈ 17.5 K)

– BCS-like feature in C(T) at 17.5 K suggests partial gapping of Fermi surface by CDW or SDW – Small moment antiferromagnetism (SMAFM): μ ≈ 0.03 μB/U, ||c-axis, (100) modulation – δS ≈ 0.2ln(2) too large ⇒ “HO” phase – Large moment antiferromagnetism (LMAFM)

• bserved at Pc ~ 5 - 15 kbar: μ ~ 0.4 μB/U

– SMAFM phase – small volume fraction of LMAFM phase that coexists with HO phase ⇒ μav ≈ 0.03 μB

• Superconductivity (SC) (Tc ≈ 1.5 K)

– Unconventional – Coexists with HO and SMAFM phases

• Ordered phases can be “tuned” with P, H, x:

– Produces LMAFM and LMFM phases – Non-Fermi liquid (NFL) behavior

Why URu2Si2 is interesting

ThCr2Si2 structure

a = 4.13 Å, c = 9.58 Å

URu2Si2: Early experiments and current issues EARLY EXPERIMENTS

• Heavy fermion superconductivity (polycrystalline specimens)

Schlabitz, Baumann, Pollit, Rauchschwalbe, Mayer, Alheim, Bredl, ZP (86)

• Anisotropy of physical properties (single crystal specimens)

Palstra, Menovsky, van den Berg, Dirkmaat, Kes, Nieuwenhuys, Mydosh, PRL (85)

• Partial gapping of the FS by CDW or SDW (polycrystalline specimens)

Maple, Dalichaouch, Kohara, Rossel, Torikachvili, McElfresh, Thompson, PRL (86)

• SMAFM – neutron scattering experiments (single crystal specimens)

Broholm, Kjems, Buyers, Matthews, Palstra, Menovsky, Mydosh, PRL (86)

FOLLOWED BY AN ENORMOUS AMOUNT OF EXPERIMENTAL AND THEORETICAL WORK

URu2Si2: Early experiments and current issues CURRENT ISSUES BEING ADDRESSED INCLUDE

• Identity of “HO” phase order parameter (OP)
• Whether SMAFM is intrinsic or extrinsic
• T-P phase diagram for ordered phases of URu2Si2;

e.g., Pc(T) where LMAFM forms

• T-x and T-H phase diagrams (for various substituents)
• NFL characteristics of properties near HO, AFM and FM QCPs
• Nature of the unconventional SC

• Superconductivity below Tc ≈ 1.5 K (onset)
• BCS-type mean field transition at To = 17.5 K

– δC ≈ Aexp(-Δ/T); Δ ~ 102 K ⇒ SDW or CDW – γ(0)/γ’ ≈ 0.6 ⇒ ~ 40 % Fermi surface removed by SDW or CDW – SC & SDW or CDW compete for Fermi surface!

• δS ≈ 0.2ln(2) too large for AFM with small μ ≈ 0.03 μB ⇒ Hidden order (HO)?

Low temperature specific heat of URu2Si2

C’(T)/T=γ’+βT2 C(T)/T=γ+βT2

SCing transition

Maple, Dalichaouch, Kohara, Rossel, Torikachvili, McElfresh, Thompson, PRL (86)

Effect of pressure on competing electronic states in URu2Si2

McElfresh, Thompson, Willis, Maple, Kohara, Torikachvili ‘87

Low temperature specific heat of URu2Si2 under pressure

NOTE: Rapid suppression of specific heat jump ΔC at Tc with P

• R. A. Fisher, S. Kim. Y. Wu,
• N. E. Phillips, M. W. McElfresh,
• M. S. Torikachvili, M. B. Maple, 90

n(P) calculated from Tc & T0 and γ(P=0) C(T) measured under P

• R. A. Fisher et al., Physica B (90)
• M. B. Maple et al., PRL (86); J. R. Jeffries,
• N. P. Butch, B. T. Yukich, M. B. Maple, PRL (07)
• Bilbro & McMillan PRB (76)

– Theory – CDW/SDW competes with SCing order to gap a simple FS – HO/SMAFM and SCing phases compete for electrons

• n = γ0/γnorm

– Amount of FS not gapped by CDW/SDW – C(T): n(0) = 0.58, Tc0 = 3.9 K

URu2Si2: Fermi surface competition Tc0 = Tc(P)n(P)T0(P)1-n(P)

URu2Si2: HO/SMAFM – LMAFM phase transition under P

• H. Amitsuka et al., PRL (99)
• K. Matsuda et al., JP:CM (03)

Neutron diffraction: AFM μ increases with P

29Si NMR: phase separation –

AFM volume increases with P (HO volume decreases with P)

PM AFM

Pc ≈ 15 kbar

• G. Motoyama et al., PRL (03)
• F. Boudarot et al., Physica B (03)

URu2Si2: HO/SMAFM – LMAFM phase transition under P Neutron diffraction Thermal expansion α(T,P) How is SC affected through HO/SMAFM – LMAFM phase transition near ~5 kbar at low T?

• Objectives — Determine:

– Nature of HO/SMAFM phase – Whether SMAFM is intrinsic or extrinsic – T-P phase diagram for ordered phases of URu2Si2; e.g., Pc(T) where LMAFM forms – Relationship between HO and SCing phases – Non-Fermi liquid characteristics of properties near HO and FM quantum critical points

• Approach

– Tune ordered phases with P, H, and chemical substitution (Re for Ru) – Prepare single crystals of URu2-xRexSi2 – Perform measurements of ρ(T, H, P, x): 50 mK ≤ T ≤ 300 K 0 ≤ H ≤ 9 T 0 ≤ P ≤ 30 kbar 0 ≤ x ≤ 0.6 URu2Si2: Objectives and approach

ρ(T,P): HO/SMAFM – LMAFM phase transition under P URu2Si2 single crystal Kink in To(P) suggests transition from HO/SMAFM to LMAFM phase at ~15 kbar ?

kbar K 0.10 dP dT0 ≈ kbar K 0.23 dP dT0 ≈

= =

Scattering of electrons by gapped AFM magnons: ρ(T) = ρo+AT2+B(T/Δ)[1+2(T/Δ)]exp(-Δ/T)

Hessel Anderson ‘80

ρ(T,P): HO/SMAFM – LMAFM phase transition under P URu2Si2 single crystal

Superconductivity under pressure – Tc(P) Tc decreases smoothly with P and vanishes in the vicinity of the HO/SMAFM – LMAFM phase transition at ~15 kbar URu2Si2 single crystal

Superconductivity under pressure – Tc(P) & Hc2(T,P) URu2Si2 single crystal

Phenomenological fits to Hc2(T) data: Hc2(T) = Hc2(0)[1 - A(T/Tc)2]

No changes in Tc(P) and Hc2(T,P) curves to ~15 kbar ⇒ no qualitative change in SC due to onset of LMAFM phase, if it were to occur near 5 kbar!

Amitsuka et al, JMMM (07) Knebel et al, JMMM (07)

URu2Si2: T-P phase diagram Explore behavior of Pc(T) by exploiting reduction of T0 with x in URu2-xRexSi2

24

Cr

25

Mn

26

Fe

27

Co

28

Ni

42

Mo

43

Tc

44

Ru

45

Rh

46

Pd

74

W

75

Re

76

Os

77

Ir

78

Pt

106

Sg

107

Bh

108

Hs

109

Mt

110

Ds

4d75s1 4f145d56s2

URu2Si2: Re substitution

URu2-xMxSi2 (M = Re,Tc) ⇒ FM!

• Y. Dalichaouch, M. S. Torikachvili,
• M. B. Maple, A. L. Giorgi PRB (89)
• E. D. Bauer, V. S. Zapf, P.-C. Ho, E. J. Freeman,
• C. Sirvent, M. B. Maple, PRL (05)

ρ(T) ≈ ρ(0)[1 + (T/To)n]

URu2-xRexSi2: T-x phase diagram (polycrystals)

FM QCP

URu2-xRexSi2 T-x phase diagram: ρ(T,x) & χ(T,x)

*curves offset for clarity

Single crystals

Peaks in M/H curves coincide with Curie temperatures inferred from M2 vs H/M “Arrott plots”

100 Oe

URu2-xRexSi2: T-x phase diagram

Single crystals

URu2-xRexSi2: ρ(T,x) under pressure Single crystals

Amitsuka et al., JMMM (07) Knebel et al., JMMM (07)

URu2Si2: T-P phase diagrams

• There appears to be a steep

(vertical?) phase boundary at Pc ≈ 15 kbar (nearly independent

• f T - red line in figures)
• HO/SMAFM - LMAFM phase

boundary or another phase boundary?

• Lower phase diagram favored by

continuous behavior of Tc(P) and Hc2(T,P)

• Upper phase diagram could be

favored is rapid diminution of ΔC at Tc near 6 kbar signals loss of bulk SC (come back to this later in another context)

URu2Si2: Analysis of ρ(x,T) x ≤ 0.06 (HO/SMAFM): FL + gap x ≥ 0.10 (PM, FM): Power law

URu2-xRexSi2: Magnon gap Δ and exponent n of ρ(T) Single crystals n: ρ = ρo+ATn

Δ: ρ(T)=ρo+AT2+B(T/Δ)[1+2(T/Δ)]exp(-Δ/T)

Hessel Anderson ‘80

n

C(T)/T = γo – colnT

URu2-xRexSi2: Specific heat

Single crystals Single crystals

C(T)/T = γo – colnT) ρ(T) ∝ Tn (n ≈ 1 - 1.5)

URu2-xRexSi2: T-x phase diagram (single crystals)

• Transition from HO/SMAFM to LMAFM phase in URu2Si2 under P

appears to occur at Pc ≈ 15 kbar (Kink in T0(P) at ~15 kbar)

• Pc appears to be independent of T

(Kink in T0(P) always occurs at 15 kbar in URu2-xRexSi2, even though T0 decreased by Re substitution)

• Mechanism underlying superconductivity unchanged up to ~15 kbar

(No features in Tc(P) or Hc2(T,P) of URu2Si2 indicative of transition from HO to LMAFM phase below 15 kbar)

• Tc of URu2Si2 suppressed near Pc ≈ 15 kbar
• How can T-independent Pc be reconciled with other published phase

diagrams? (Possible reason – strains in URu2Si2 samples produced by pressure transmitting medium used in other experiments – usually, Flourinert)

• Picture of partial gapping of the Fermi surface by HO/SMAFM and

SCing phases consistent with present experiments

• Suggests HO phase associated with CDW/SDW-like phenomenon
• Non-Fermi liquid behavior in URu2-xRexSi2 near HO and FM QCPs

Summary

Coworkers

University of California, San Diego

• J. J. Hamlin, T. A. Sayles, D. A. Zocco

Stanford University J.-H. Chu, I. R. Fischer

More information – this conference Poster:

Superconductivity, magnetism and charge density waves in rare earth tritellurides under pressure

• J. J. Hamlin, D. A. Zocco, T. A. Sayles, M. B. Maple, J.-H. Chu, I. R. Fischer

Talk:

Infrared and Raman study of the charge-density-wave ground state

• L. Degiorgi

Interplay of superconducting, charge density wave, and magnetic order in rare earth tritelluride RTe3 compounds

Rare earth tritellurides: RTe3

• E. DiMasi, M. C. Aronson, J. F. Mansfield, B. Foran, S. Lee, PRB 52,14516 (1995)
• N. Ru, I. R. Fisher, PRB 73, 033101 (2006)
• J. Lavarock, S. B. Dugdale, Zs. Major, M. A. Alam, N. Ru, I. R. Fisher, G. Santi, E. Bruno, PRB 71, 0851144 (2005)
• N. Ru, J. -H. Chu, I. R. Fisher, PRB 78, 012410 (2008)
• TCDW1 decreases and TCDW2

increases with decreasing a

• Suggests similar dependence
• f TCDW1 and TCDW2 on P

฀ ρ(T) measurements under P

SCing, CDW, and AFM order under pressure in TbTe3

• Interplay of CDW, AFM & SC
• P-induced SC
• CDW, AFM, SC coexist (~23 kbar)
• Opportunity to study magnetically
• rdered SCs under P
• J. J. Hamlin, D. A. Zocco,
• T. A. Sayles, M. B. Maple,

J.-H. Chu, I. R. Fischer, 08

Evidence for antiferromagnetic ordering of Tb3+ ions in TbTe3

• J. J. Hamlin, D. A. Zocco, T. A. Sayles,
• M. B. Maple, J.-H. Chu, I. R. Fischer, 08

Pressure dependence of antiferromagnetic order in CeTe3

• D. A. Zocco, J. J. Hamlin,
• T. A. Sayles, M. B. Maple,

J.-H. Chu, I. R. Fischer, 08

Coworkers

University of California, San Diego

• R. E. Baumbach, J. J. Hamlin, T. A. Sayles, D. A. Zocco

Oak Ridge National Laboratory

• R. Jin, D. Mandrus, M. A. McGuire, B. C. Sales, A. S. Sefat

Lawrence Livermore National Laboratory

• J. R. Jeffries, S. T. Weir

University of Alabama, Birmingham

• Y. K. Vohra

High temperature superconductivity and spin density waves in transition metal pnictides

More information – this conference Posters:

Superconductivity and magnetism in Fe-based pnictides under pressure

• R. E. Baumbach, J. J. Hamlin, D. A. Zocco, T. A. Sayles, M. B. Maple, M. A.

McGuire, A. S. Sefat, B. C. Sales, R. Jin, D. Mandrus, J. R. Jeffries, S. T. Weir,

• Y. K. Vohra

Pressure dependence of electronic ground states in f-electron materials

• D. A. Zocco, J. J. Hamlin, R. E. Baumbach, T. A. Sayles, N. P. Butch, M. B.

Maple, J.-H. Chu, I. R. Fischer, M. A. McGuire, A. S. Sefat, B. C. Sales, R. Jin,

• D. Mandrus, J. R. Jeffries, S. T. Weir, Y. K. Vohra

Talks:

Recent results from Oak Ridge National Laboratory on the layered iron arsenide superconductors with Tc = 55 K Brian C. Sales Multiband effects in Fe-pnictide superconductors Zlatko Tesanovic High temperature superconductivity – what can be expected in the future? Jorge Hirsch

High temperature superconductivity and spin density waves in transition metal pnictides

Superconductivity in oxypnictides

• Recent developments in high Tc superconductivity

–LnFeAsO1-xFx Maximum Tc ≈ 55 K (Ln = Sm) Structure type: ZrCuSiAs (1:1:1:1) –A1-xMxFe2As2 Maximum Tc ≈ 38 K (A = Sr, M = K, Cs; A = Ba, M = K) Structure type: ThCr2Si2 (1:1:2)

• Superconductivity

–Periodically declared to be “all over” –Resuscitated by developments in materials; e.g., Magnetic superconductors (~75) Organic superconductors (~75) Heavy fermion superconductors (~80) High Tc cuprate superconductors (~86) High Tc oxypnictide superconductors (~08)

Structure type: ThCr2Si2 Structure type: ZrCuSiAs

• K. Sasmal, B. Lv, B. Lorenz, A. Guloy, F. Chen,
• Y. Xue, C. W. Chu, arXiv:0806.1301 (2008)

Structure of oxypnictide 1:1:1:1 and 1:2:2 superconductors

LnFeAsO1-xFx high Tc superconductors

SmFeAsO1-xFx

Liu et al. arxiv:0804.2105 Nomura et al. arxiv:0804.3569

LaFeAsO1-xFx

• J. J. Hamlin, R. E. Baumbach, D. A. Zocco,
• T. A. Sayles, M. B. Maple, J. Phys.: Cond. Matt. 08

Superconductivity in LaFePO

• LaFePO single crystals grown

in Sn flux

• Superconductivity: Tc = 6.7 K
• Significant anisotropy of

resistively determined Hc2(T) curves

• J. J. Hamlin, R. E. Baumbach, D. A. Zocco,
• T. A. Sayles, M. B. Maple, JPCM 08

Superconductivity in LaFePO

• No measurable jump in C(T) at Tc = 6.7 K
• Very small superconducting fraction?
• Superconductivity due to oxygen defects?
• Gapless superconductivity?
• P-dependent phase separation?
• Reminiscent of URu2Si2

Tc

Oxypnictide superconductors: pressure dependence of Tc

• D. A. Zocco, J. J. Hamlin, R. E. Baumbach, M. B. Maple,
• M. A. Maguire, B. C. Sales, A. S. Sefat, R. Jin, D. Mandrus,
• J. R. Jeffries, S. T. Weir, Y. K. Vohra, J. Superconductivity 08
• J. J. Hamlin, R. E. Baumbach, D. A. Zocco,
• T. A. Sayles, M. B. Maple, J. Phys.: Cond. Matt. 08
• Dome-shaped dependence of Tc on P
• Reminiscent of Tc vs x in cuprates and

Tc vs P in heavy fermion compounds

R(Ω)

Electrical resistivity of CeFeAsO under pressure

Poster: Pressure dependence of electronic ground states in f-electron materials

• D. A. Zocco, J. J. Hamlin, R. E. Baumbach, T. A. Sayles, N. P. Butch, M. B.

Maple, J.-H. Chu, I. R. Fischer, M. A. McGuire, A. S. Sefat, B. C. Sales, R. Jin,

• D. Mandrus, J. R. Jeffries, S. T. Weir, Y. K Vohra

No evidence of superconductivity to ~550 kbar! (diamond anvils)