Visualizing out-of-equilibrium superconductivity

Transcription

1 Strongly disordered and inhomogenous superconductivity- Grenoble Visualizing out-of-equilibrium superconductivity Claude Chapelier, INAC, CEA - UGA Eduard Driessen, IRAM 1- Superconducting Photon detector 2- Critical current microscopy 3- Where do the subgap states come from?

2 Superconducting photon detector f 0 = 1 2π LC L = m n s e 2 = ħ R n π T tanh (T) 2k B T P.K. Day et al., Nature 425, 817 (2003)

3 Superconducting photon detector E.F.C. Driessen et al., Phys. Rev. Lett. 109, , (2012) P.C.J.J. Coummou et al., Phys. Rev.B 88, (R), (2013) f 0 = 1 2π LC L = m n s e 2 = ħ R n π T tanh (T) 2k B T P.K. Day et al., Nature 425, 817 (2003)

4 Superconducting photon detector E.F.C. Driessen et al., Phys. Rev. Lett. 109, , (2012) P.C.J.J. Coummou et al., Phys. Rev.B 88, (R), (2013) f 0 = 1 2π LC L = m n s e 2 = ħ R n π T tanh (T) 2k B T

5 Superconducting photon detector E.F.C. Driessen et al., Phys. Rev. Lett. 109, , (2012) P.C.J.J. Coummou et al., Phys. Rev.B 88, (R), (2013) f 0 = 1 2π LC L = m n s e 2 = ħ R n π T tanh (T) 2k B T Tc = 3,5 K M.V. Feigelman and M.A. Skvortsov, Phys. Rev. Lett. 109, (2012) A.I. Larkin and Yu. N. Ovchinnikov, Sov. JETP 34, 1144 (1972) A. Bespalov et al, Phys. Rev. B 93, (2016) A. Bespalov et al, arxiv:1603,04273v1 (2016) A. Silva et al., Phys. Rev. B 72, (2005)

6 Superconducting photon detector N qp τ r = τ 0N 0 k B T c 3 V 2Δ 2 P opt = N qp τ r 2 α N qp δa, δf α δn qp δa, δf δp opt δp opt 1 2 α P opt δa δp opt J. Bueno et al., Appl. Phys. Lett. 105, , (2014) δf δp opt ~ cste J. Hubmayr et al., Appl. Phys. Lett. 106, (2015)

7 Superconducting photon detector N qp τ r = τ 0N 0 k B T c 3 V 2Δ 2 P opt = N qp τ r 2 α N qp δa, δf α δn qp δa, δf δp opt δp opt 1 2 α P opt δa δp opt δf δp opt ~ cste J. Gao et al., Appl. Phys. Lett. 101, (2012) J. Bueno et al., Appl. Phys. Lett. 105, , (2014) J. Hubmayr et al., Appl. Phys. Lett. 106, (2015)

8 Superconducting photon detector N qp τ r = τ 0N 0 k B T c 3 V 2Δ 2 P opt = N qp τ r 2 α N qp δa, δf α δn qp δa, δf δp opt δp opt 1 2 α P opt Understanding the recombination physics in is required J. Gao et al., Appl. Phys. Lett. 101, (2012) J. Bueno et al., Appl. Phys. Lett. 105, , (2014) J. Hubmayr et al., Appl. Phys. Lett. 106, (2015) Sacépé et al., Phys. Rev. Lett. 101, (2008)

9 Critical current microscopy 2- Critical current microscopy

10 STM Critical on current an nanowire microscopy Vt It 100 MΩ to feedback electronics and lockin 10 MΩ Device fabrication in Kavli Nanolab Nanowire: 5nm x 200 nm x 4 µm Tc = 1.5 K, Rs = 1.5 kω D = 250 mv, D/ Tc = 1.9 E. Driessen et al., unpublished

11 Critical current microscopy Topography DOS (E F ) E. Driessen et al., unpublished

12 Critical current microscopy Local non-equilibrium! Vt It 100 MΩ In 10 MΩ to feedback electronics and lockin Vn It = 1nA E. Driessen et al., unpublished

13 Critical current microscopy Long live time of quasiparticles close to the gap Vt It 100 MΩ In 10 MΩ to feedback electronics and lockin Vn It = 200pA It = 500pA It = 2nA It = 1nA

14 Critical current microscopy Local non-equilibrium! Vt It 100 MΩ In 10 MΩ to feedback electronics and lockin Vn It = 1 na, Vb = 2 mv E. Driessen et al., unpublished

15 Critical current microscopy Long live time of quasiparticles close to the gap Vt It 100 MΩ In 10 MΩ to feedback electronics and lockin Vn It = 200pA It = 500pA It = 2nA It = 1nA

16 TIN Superconductor-Insulator transition B. Sacépé et al., Nat. Comm., (2010) R [k ] ,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 T [K] T c [K] Δ/T c ,0 2,0 2,0 G(V), normalized 1,5 1,0 0,5 D = 154 µev T eff = 0,35 K G(V), normalized 1,5 1,0 0,5 D = 225 µev T eff = 0,32 K G(V), normalized 1,5 1,0 0,5 D = 260 µev T eff = 0,25 K 0,0-1,0-0,5 0,0 0,5 1,0 V [mv] 0,0-1,0-0,5 0,0 0,5 1,0 V [mv] 0,0-1,0-0,5 0,0 0,5 1,0 V [mv] Increasing disorder Sacépé et al., PRL 101, (2008)

17 TIN Superconductor-Insulator transition di/dv (a.u.) V (mv) Device fabrication in Kavli Nanolab Nanowire: 5nm x 200 nm x 4 µm Tc = 1.5 K, Rs = 1.5 kω D = 250 mv, D/ Tc = 1.9

18 Where do the subgap states come from? 3- Where do the subgap states come from?

19 Where do the subgap states come from? Δ/T c = 1.76 h D 2 2 θ x 2 + ie Γ in 2Γ sf cos θ sin θ + Δ(x) cos θ = 0 n E, x = n 0 Re cos θ(e, x) ds,n di/dv 3,0 2,5 2,0 1,5 x exp = 0 nm x cal = 0 nm x exp = 12 nm x cal = 9 nm x exp = 20 nm x cal = 21 nm x exp = 32 nm x cal = 31 nm 1,0 0,5 W. Escoffier et al., Phys. Rev. Lett. 93, (2004) 0,0-1,5-1,0-0,5 0,0 0,5 1,0 1,5 E (mev)

20 Where do the subgap states come from? C. Gong et al., J.Mater. Chem. 21, (2011)

21 Conclusion Disordered superconductors are promising materials for photon detector however, quasipartricle dynamic must be understood Critical current microscopy is a powerful tool in order to probe out-of-equilibrium superconductivity Materials must be well controlled and characterized