Institute of Physics, CAS

Pressure-induced magnetic quantumPressure induced magnetic quantum critical point and unconventional 

superconductivity in CrAs and MnPsuperconductivity in CrAs and MnP

Jinguang ChengJinguang Chengjgcheng@iphy.ac.cn

School�and�Workshop�on�Strongly�Correlated�Electronic�Systems-Novel�Materials�and�Novel�Theories ICTP�Trieste 2015 8.10-21

Collaborators

J. L. Luo, W. Wu, J. P. Sun, C. Q. Jin, P. J. Sun, N. L. Wang 

Y. Uwatoko, K. Matsubayashi

M. Matsuda, J. Q. Yan

Q. Si QR. Yu

OUTLINE 

1 QCP d ti l SC1

2

QCP and unconventional SC

2 P-induced SC in CrAs

3 P-induced SC in MnP

4 Conclusion and outlooks

Quantum critical point (QCP)*/T m /m0

TN

Ordered phase

Fermi liquid

0

p liquid

(x, P, H, etc)cQCP

Non Fermi liquidn

SCColeman & Schofield, Nature (2005)Si & Steglich, Science (2010)Sachdev & Keimer, Phys. Today (2011)

T n (1  n < 2) Ce/T  lnT

QCP and unconventional SC

Chemdopin m

ical ng

Pressuure

Advantages clean fine and precise

Cr- and Mn-based superconductor?

SCSC

OUTLINE 

1 QCP d ti l SC1

2

QCP and unconventional SC

2 P-induced SC in CrAs

3 P-induced SC in MnP

4 Conclusion and outlooks

1st order AF transition of CrAs 

Helimagnetic structureOrthorhombic MnP‐type  crystal  structure

1.7μB/Cr

4%

Pnma (62)a = 5.6680 Å b = 3.4670 Å 

6 2210 Å

2

3 44 ~4%c = 6.2210 Å

1,2= 3,4=‐120Q = 0.3532c*

1 12

TN = 265 KActa. Chem. Scan. 25, 1703 (1971); JPSJ 30, 1319 (1971)

2,3= 4,1=+183

Earlier high pressure studies and motivation

TNN

AFAF

? What will happen at the magnetic critical point?

Sov. Phys. JETP 51, 542 (1980)

g pSuperconductivity??

High-quality CrAs single crystals are important

a

1mm

HP measurements on the CrAs crystals

Piston‐cylinder cellPressure manometer: Pb

Resistivity Ac magnetic susceptibility

Pressure manometer: PbP(kbar) = (7.2‐Tc)/0.0365

Pressure medium:      GlycerolGlycerol

Pb CrAs

Pb+CrAs

Discovery of P-induced SC in CrAs

#6 RRR 2402.0

1.5

m)

1 bar6.97 400

1 bar1.73 kbar

#6 RRR =240

1.0

0.5 (

cm

2.01

3.28 4.47

(b)3003.15

0.03.02.01.0

T (K)

(b)300

200(

cm

) 4.06

4.98T (K)200

100

(

5.75

6.97

1.5

1.0cm) 21.37

9.50

15.0218.55

100

(a)0.5

0 0

(

8.30

9.50

10.88 (c)0

3002001000T (K)

0.02.01.51.0

T (K)

10.88

Bulk SC evidenced from ac susceptibility  

0.02.86 kbar 4.09

-0.2 4.99

9 69-0.4

4 6.40

9.69

20.86

-0.6

7.85 16.19-0.8

7.85

-1.02.01.51.00.5

T (K)

T-P phase diagram of CrAs300

250#6, #7, #9, TN

cool from

#9, TNwarm from

TNwarm from dc-

200

150

T (K

)TN #6, #7, #9, Tc

0 from

#6, Tc0 from ac-

#7a, Tc0 from in PCAC

100

50

T

20 T

AF AF+SC(a)

RRR #6 240#7 32750

01.0

4K

12

20 Tc

Bulk SC# 9 250

0.5

|4

| T=0.

4

4

0.12

4

Tc (K

)

(b)

706050403020100Pressure (kbar)

0.0 4

706050403020100

A2Cr3As32 3 3 (A=K, Rb, Cs)

(G. Cao, Zhejiang Univ.)

PRX (2015)PRB (2015)

Kotegawa, JPSJ (2014) ,  PRL (2015)

SCM(2015)

SC sensitive to disorder#3 RRR = 45

400

#31 bar 12 1.25

P / kbar

250

200

#3 #4TN

300

#3 RRR = 45 2.02 kbar

2.55

3 21

10

8

6

1 bar

0.55

2.16

150

100

T (K

)

200

(

cm

)

3.21

4.07

4.90

4

2

0

(

cm

)

12 100

50 Tc× 30100

5.70

10

8

6

2.163.884.88

6.547.20

11.44

0

1086420P (Kbar)0

4

2

0

2.69 3.2216.24

300250200150100500T (K)

2.01.51.00.50.0T (K)

Coherent length vs Mean free path1.0

0.8

RH 2.610‐10 m3/C at 5 Kn = 2.4 1028 m‐3

0.6

0 4 0H

c2 (T

)

P = 9. 5 kbar Lmfp=0.4

0.2

P 9. 5 kbar 0Hc2(0) = 0.96(2) TTc(0) = 1.506(5) K = 1.41(6)

mfp

RRR ~2500.0

1.61.20.80.40.0Tc (K)

H (T) H (0) {1 [T /T (0)]α}

RRR  250 0 = 2 10‐8 mLmfp = 766 Åμ0Hc2(T) = μ0Hc2(0) {1‐[Tc/Tc(0)]α}

Åμ0Hc2(0) = 0/22

mfp

RRR ~50 10 10 8 = 185 Å  0 = 10 10‐8 m

Lmfp = 153 Å

Neutron scattering： Phys. vs Chem. PSt t M ti d

3.60

3.55(a)

Structure Magnetic order

3.50

3.45

1 ba

r

3.5

kbar

9 kb

ar

kbar

Physical pressure

3.40

3.35

b (Å

)

3.606.

9.1

(c)

12 kbar

3.55

3.50

(c)

x = 0.0 x = 0.035

Chemicalpressure

3.45

3.40

3 35

x = 0.05

pressure

CrAs1‐xPx3.35

3002001000T (K)

Inelastic neutron scattering

CrAs300K

P6%50K

CrAs100K

NNN AFM correlations

Evidence for quantum criticality: Enhanced m*

4.5

4 02.23 4.896.20

7.37

9.13

P (kbar)

der c

ell 4

cm)

(b)

4.0

3.5

m)

3.75 11.17

13.14 19.1721.65 Pi

ston

cyl

id

3

2

0 (

c

3.0

2 5

(

cm 1.31

20

25 ic c

ell

2

30

25

) (c)2.5

2.0

3035455570

Palm

Cub

i

20

15

10A (1

0-9

cm (c)

1.5

100806040200

70 10

5

0

A

6040200

(a)Pc

100806040200T2(K2)

6040200P (Kbar)

Enhancement of A coefficient near Pc; A (m*/m0)2

Evidence for quantum criticality: nFL55

P (kbar)

2 23

6.207.379.1311.17

der c

ell

4

2.23

3.75

4 89

19.17

21.65

Pist

on c

ylin

d

3

(

cm

)

20

251.31

4.89 13.14

Pic

cel

l

2.0

2

3035

4555

Palm

cub

i

1.5n

#92 5570

= +BTn

1.5 #9 #6 #7

Pc

112108642

T (K)

= 0+BTn 1.0706050403020100

P (kbar)

Further evidences for quantum criticality2 0

T (K )

2.0

1.5

1 0 c

m) (f)

CrAs1-xPx

0.045

0.07x

40

mol

K2 )

(h)0.0450.05

0.2

x

1.0

0.5- 0

(

0.0

0.030.20.04 20

0

C/T

(mJ/

m

2

CrAs1-xPx

0.00.030.040.1

0.0

100806040200T2 (K2)

0

6040200T2 (K2)

( )20

700

600

500

CrAs1-xPx x = 0.00 x = 0.03 x = 0.04

0 045

30

20

(m

J/m

20

15

10 c

mK

-2)

A

500

400

300 (

cm

)

x = 0.045 x = 0.05

20

10

mol K

2)

10

5

0

A (1

0-9

(g)xc

A

200

100

0

0.200.150.100.050.00x in CrAs1-xPx

0

0350300250200150100500

T (K)

Mn-based superconductor?

Nat. Comm. 5, 5508 (2014)

SC

Mn-based superconductor?

Strategy

4.0

3.5MnSb

MnAs

Magnetic moment vs. b‐axis length

M X3.5

3.0

2.5

)

CrSb

M X

2.0

1.5

M (

B)

CrAsMnP

MnAs0.88P0.12

a1.0

0.5

0.0CrP

CrAs0.9P0.1

c4.03.53.0

b (Å)

H l NiA ( lid li )

b

MnP would be the a good start point Hexagonal NiAs (solid line) Orthorhombic MnP (dash lines)

MnP would be the a good start point to approach a magnetic instability by the application of high pressure!!!

Physical properties of MnP at ambient pressure1.4

1.2

1.0

0 83+)

H // b 6

50.8

0.6

0.4M(

B/M

n 5

4

T) PM

0.2

0.0

250

H b 3

2

H (T

Fan

250

200

150 c

m)

I b

Ts

1

0 ScrewFM//b

100

50

(

I // b

Tc

350300250200150100500T (K)

03002001000

T (K)

cTc = 291.5 K Ts 50 K

Earlier high-pressure studies

J. Solid State Chem. 4, 391 (1972)

30 50 kb S lid PTM30‐50 kbar: Solid PTM

HP techniques with extended pressure capacity

C bi il llCubic anvil cell Opposed-Anvil Cell

P 15 GPPmax : 15 GPaP-medium :

Glycerol

Pmax : 12 GPaP di A

Cheng JG, RSI (2014)

P-medium : Ar

Kitagawa, JPSJ (2010)

R(T) @HP: Cubic anvil cell2 0

12

8

4/dT

(a.u

.)

0 GPa2.8

5.0

6.47.4

8.1

(b)

2.0

1.5

1 0 c

m) 6.4

7.48.1

10 78.7 9.3

#1

200 6.4

4

0

d/

#1

1.0

0.5

0 0

(

0 GPa2.8

5.010.7

200

150

c

m) 0 GPa2.8

5.07.4

10.7

0.02.01.51.00.50.0

T (K)

1.0 6 3# 2#2100

50

(

8.1 (a)

1.0

0.8

0.6

(

cm

)

4.2

6.3

6.77.8 8.7

9.7

# 2#2

03002001000

T (K)

0.4

0.2

0.0

(

0 GPa

7.17.5

2.01.51.00.50.0T (K)

P suppresses the magnetic transition; Possible SC appears near the magnetic instability; P may alter the nature of magnetic transition

R(T) @ HP: Opposite anvil cell

1.2

0 8m)

(a)7.2 GPa

# 3#3

0.8

0.4 (

c 7.6 7.8

8.6

8.34.2

5.2Pb#4

0.00.0 7.2

7 6

0GPa

2.4 #4

-0.4

4

7.6

7.88.38.6 # 4

Nearly perfect diamagnetic signal confirms the P‐induced SC with a TSC 1K in MnP;

-0.8

4

(b) SC exists within a narrow pressure range where the magnetic transition just vanishes;

2.01.51.00.50.0T (K)

magnetic transition just vanishes;

T-P phase diagram of MnP50

300

250

TC300

250

TC

50

40

30

c

m)

Ts0 GPa

0.290.5

300

250

TC300

250

TC

PM250

200

250

200

20

10

0

c ( 0.86

1.07

250

200

250

200

PM

150T (K

)

150T (K

) FM 6050403020100T (K)

150T (K

)

2.52.52.52.52.52.52.5150T (K

)

2.5

100

TS

100

TS

100

TS

2.0

1.5

(a.u

.)

2.0

1.5

(a.u

.)

2.0

1.5

(a.u

.)

2.0

1.5

(a.u

.)

2.0

1.5

(a.u

.)

2.0

1.5

(a.u

.)

0 GPa

2.0

1.5

(a.u

.)

0 GPa

100

TS

T*

2.0

1.5

(a.u

.)

0 GPa0 57

T*

50

0

S50

0

S

SC

20TSC50

0

S1.0

0.5'

( 0 GPa

1.0

0.5'

( 0 GPa 0.57

1.0

0.5'

(

0 GPa 0.57 0.91

1.0

0.5'

(

0 GPa 0.57 0.91 1.36

1.0

0.5'

( 0 GPa 0.57 0.91 1.36 1.82

1.0

0.5'

( 0 GPa 0.57 0.91 1.36 1.82 1.98

1.0

0.5'

( 0.57 0.91 1.36 1.82 1.982.43

50

0

SAFM? 1.0

0.5'

( 0.57 0.91 1.36 1.82 1.98 2.434 220

1086420P (GPa)

01086420

P (GPa)

01086420

P (GPa)0.0

30025020015010050T (K)

0.030025020015010050

T (K)

0.030025020015010050

T (K)

0.030025020015010050

T (K)

0.030025020015010050

T (K)

0.030025020015010050

T (K)

0.030025020015010050

T (K)

01086420

P (GPa)0.0

30025020015010050T (K)

4.22

Signatures of AFM QCP2 02.0

7.5

7.8

1.00.80.6

cm

)

(b)1.2

1.0

(

cm

) 7.1GPa

1.5

6.3

6.77.1

8.70.40.20 0

0 (

0.812840

T1.5 (K1.5)

1.0

(

cm

)

5.2

9.7 0.016

12

c

m)

(c)

0.5 0GPa

4.28

4

0A

(10-9

Pc

0 0

GPa

(a)

01086420

P (GPa)

non‐Fermi‐liquid behavior and dramatic 0.0

100806040200T2 (K2)

enhancement of effective mass m* near Pc

Cheng et al. PRL (2015)

Conclusion and outlooks P induced magnetic QCP is an important approach to P‐induced magnetic QCP is an important approach to 

search for unconventional SC, e.g. CrAs and MnP. Expected to have more Cr‐ and Mn‐based SCs . Expected to have more Cr and Mn based SCs….

Open questions: What is the specialty for the helimagnetic QCP?  Can we also realized SC in other helimagnets: FeP, FeAs? Nature of the AFM order in MnP?