High Pressures at Low Temperatures. Manuel Núñez Regueiro

Transcription

1 High Pressures at Low Temperatures Manuel Núñez Regueiro

2 Pressure Techniques : P = F / S Hydrostatic P<3GPa (30000 atm) Liquid or He gas Quasi-Hydrostatic (Diamond Anvil Cells; <250GPa) High pressure Experimental Methods M. Eremets Oxford Science Publications (1996)

3 Hydrostatic Cell Clamp Anti-extrusion rings Piston (force) Electrical resistance Magnetic susceptibility P<3GPa Liquid Sample + Manometer Measuring leads Liquid must remain amorphous on cooling but, pressure loss on cooling Manometer : Resistive InSb probe Building Material: CuBe alloy elastic down to very low temperatures

4 Quasi hydrostatic Diamond Anvil Cell (DAC) 250GPa... pressure medium hydrostatic range of pressure mediums: Silicon oil <7GPa Ne < 30GPa He ~ 100GPa Manometer: Ruby flourescence spectra

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6 ID27- ESRF

7 What can we measure? Optical properties : Brillouin / Raman scattering, infrared absorption Structural Properties : X-rays, synchrotron radiation, neutrons Transport properties : electrical resistivity, thermoelectric power Thermal properties : specific heat Magnetic Properties : susceptibility

8 Optical properties : Example Raman Constraint : Good quality diamonds laser beam The development of optical spectroscopy instrumentation make it now possible to obtain the Raman spectra of metals to megabar (>100 GPa) if not multimegabar pressures. The information obtained includes the behavior of first-order phonon modes and their coupling to the electronic and (possibly) magnetic excitations. It can be used to estimate the elastic moduli, and to obtain diagnostics of phase transformations and electronic topological transitions. (Gontcharov et al. J. Raman.Spect.34(2003)532)

9 Magnetic Susceptibility Measurements Compensated Coil Vibrating Coil (Timofeev et al. Rev.Sci.Instrum. 73(2002) 371) (Ishikuza et al. Rev. Sci. Instrum., 66(1995)3309)

10 Electrical Resistance Measurements in DAC (Eremets et al. Science281(1998)1333)

11 Anvil Sintered Diamond Tungsten Carbide CuBe quasi-hydrostatic measurements

12 Thermoelectric Power S=ΔV/ΔT (Wilhelm & Jaccard Phys.Rev.B69(2004)214408)

13 AC Specific Heat Sintered Diamonds Problem: pressure medium should have low heat conductivity & low heat capacity Steatite good choice in this example CeRu 2 Ge 2 (Bouquet et al. Sol.State Comm. 113(2000)367)

14 Large Structure deformation Silicon under pressure : from semiconductor to superconductor (Chang, Mignot et al. Phys. Rev.Lett. 54(1985)2375)

15 B Band deformation Xq k fk fk q ε k εk q Charge density waves materials y x Diverges for k=2kf instability for 2KFphonon lattice distorsion gap formation z EF X Z Y

16 B x y z EF X Z Y filling up of the gap

17 B x y z EF X Z Y

18 Typical Examples : Linear Chalcogenides M. Núñez Regueiro, P. Monceau, A. Levy 1991

19 Small Deformation CuO 2 layers Charge Transfer in Cuprates e Charge reservoir CuO 2 layers 133 Tl-2223 T c (P) =T cmax (P){ 1- β [ n hmax -n h (P) ] 2 } n h (P) = n h + Δn h (P) Δn h (P) = P dn(p) / dp T cmax (P) = T cmax + ΔT cmax (P) ΔT cmax (P) =PdT i c (P)/ dp then : T c (n h,p) = T c (n h, 0) +{dt i c (P)/dP + 2 β T cmax dn(p) / dp (n hmax -n h )}. P+ + {- β T cmax [ dn(p) / dp ] 2 }. P 2 Tc (K) Tl Pressure (GPa)

20 Pressure increases both T c 's following a parabolic law T c (P)=T c (0)+αP-β.P 2 The obtained values for the transition temperatures are the highest ever obtained for a superconductor Monteverde et al. Europhys. Lett.72(2005)458

21 σ p xy Π p z Pressure M Γ Σ

22 The T c change with pressure is sample dependent Mg non-stoichiometry A different P=0 position of the Fermi level can explain the differences 40 SUPERCONDUCTING Tc(K) Tissen Deemyad Struzkhin Monteverde2 Monteverde PRESSURE(GPa)

23 Lifshitz Topological Transition Pressure Γ Σ Meletov et al. JETP75(2002)456

24 CaSi 2 TR6 trigonal h1 (K) T c onset starting trigonal TR6 phase starting tetragonal phase CaSi Pressure (GPa) tetragonal in collaboration with M. Affronte, S. Sanfilippo, G. Olcese

25 TR6 (Rhombohedral) in collaboration with P. Bordet M. Hanfland AlB 2 : isostructural to MgB 2 h1

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27 Trigonal h1 AlB 2 h1

28 New Iron HTSC Supercondcutors: FeSe New High T c High Pressure Phase G. Garbarino, MNR, A. Sow, P. Lejay A. Sulpice, P. toulemonde, EPL86(2009)27001 LNCMI

29 Increasing the interaction between sublattices Na x CoO 2 - Screened electrostatic interactions Na ordering - Na-Na interaction stronger than Na-Co - Charge and magnetic orderings on CoO 2 at low energy scale Affected by Na ordering z=0 z=0.5c - Na(2) is ~0.1eV/Na lower in energy than Na(1) For x=0.50 occupied in equal ratios Zhang et al PRB 71 p (2003)

30 Na 0.50 CoO 2 P=1GPa Fixed Cycling temperature resistance increase Single crystal In each cycle charge carrier are localized in "pinning" positions. Cycling in temperature under pressure causes disordering of the Na sublattice due to the enhancement of the interaction with the CoO 2 sublatice

31 Pressure-induced contact between nanotobject: Carbon Nanotubes Network of Luttinger liquid tunneling Junctions -0.4 SWNT ropes Origen: Bernier Medicion: 4W ( ) Log(G) -0.6 Τ α -0.8 P Log(G) 3.0 GPa Log(G) 5.0 GPa Log(G) 7.0 GPa Log(G) 10.0 GPa Log(G) 13.2 GPa Log(G) 17.0 GPa Log(G) 20.0 GPa Log(T)

32 α = (g 1 + g 2) (8N) 20 Sample A Sample B 13 GPa Sample C 1/Alfa 15 8 For a LL of 2N channels: α N b-b = α b-b / N so the number of channels increases with pressure Why linearly? Doping! O 2 <α> α <α> α /2α bulk P (GPa) 0

33 SWNT ropes Origen: Bernier Medicion: 4W ( ) 13.2 GPa 1/Alfa IVesc 4W Vibr. Freq. (cm -1 ) /Alfa P (GPa)

34 P large diameter or disorder α log time dependence : disordered system (e.g. spin glasses) time (h)

35 SUMMARY Pressures up to 250GPa can be attained Large spectra of physical properties can be studied Ideal probe to seek for new interesting phases Alternative probe for classical problems