Disordered Solids real crystals spin glass glasses Grenoble 21.09.11-1
Tunneling of Atoms in Solids Grenoble 21.09.11-2
Tunneln Grenoble 21.09.11-3
KCl:Li Specific Heat specific heat roughly a factor of 10 higher at 0.5 K Grenoble 21.09.11-4
Li-Tunneling Systems in KCl-Crystals Li + substitutes K + ionic radius: 8 off-center positions in 111 direction Li + K + Cl - tunnel splitting: (100)-plane with Grenoble 21.09.11-5
Isotope effect Schottky-Anomaly number density Grenoble 21.09.11-6
Dielectric Susceptibility number denstiy dipole moment Grenoble 21.09.11-7
Thermal Conductivity of KCl:Li Isotope effect l = 4 mm Grenoble 21.09.11-8
KCl:Li Specific Heat, Concentration Dependence Grenoble 21.09.11-9
Dielectric Susceptibility, Concentration Dependence Grenoble 21.09.11-10
Interacting Tunneling Systems Grenoble 21.09.11-11
Transition to Incoherent Tunneling defects in crystals: at high concentrations cross over to incoherent tunneling consequences: reduced resonant contribution new phononless relaxation channel incoherent tunneling in glasses at very low temperatures? Grenoble 21.09.11-12
Atomic Tunneling Systems in Glasses Grenoble 21.09.11-13
Atomic Tunneling Systems in Glasses Grenoble 21.09.11-14
Specific Heat broad distribution of low-energy excitations Grenoble 21.09.11-15
Thermal Conductivity strong coupling to phonons systems are localized Grenoble 21.09.11-16
Universality Grenoble 21.09.11-17
Atomic Tunneling Systems in Glasses energy splitting tunnel splitting distribution function elastic, dielectric und thermal properities Grenoble 21.09.11-18
Thermal Properties in the Tunneling Modell Spezifische Wärme: Wärmeleitung: Grenoble 21.09.11-19
Elastic and Dielectric Properties resonant processes relaxational processes modulation of T < 1 K one-phonon relaxation wide distribution even for fixed E Grenoble 21.09.11-20
Heat Release Grenoble 21.09.11-21
Sound Velocity and Internal Friction Grenoble 21.09.11-22
Elastic Measurements with Mechanical Oscillators SEM picture 1 µm silver film good thermalization laser-cut glass neck 2 cm torsion bending torsion M. Heitz 2000 Grenoble 21.09.11-23
Sound Velocity discrepancy at low temperatures Grenoble 21.09.11-24
Internal Friction T < 30 mk additional relaxation channel Grenoble 21.09.11-25
Dielectric Constant Magnetic Field Independent? E polar vector, B axial vector inversion symmetry of glasses no linear terms! Naughton et al. (4.2 K, 16 T) Wiegers et al. (2 mk, 9 T) Grenoble 19.09.07-26
Dielectric Constant at Ultra-low Temperatures 20 µt dielectric constant follows field variations extremely high sensitivity to magnetic fields B = 0.1 T δε/ε 0.01 Grenoble 21.09.11-27
Temperature Dependence Grenoble 21.09.11-28
Coherent Properties coherent regime two-pulse polarization echoes: 1 GHz microwave cavity Rabi frequency 1 GHz 50 mk Grenoble 21.09.11-29
Echo Theoretical Background I coherent regime: two level approximation: applied field: Schrödinger equation: mit ansatz: Rabi frequency: Grenoble 21.09.11-30
Echo Theoretical Background II polarisation vector: Bloch equations: τ 1 : energy relaxation T < 1 K one phonon prozess...? τ 2 : phase coherence time τ 1 processes spectral diffusion spin diffusion...? Grenoble 21.09.11-31
Two Pulse Echo I polarization vector rotating frame Grenoble 21.09.11-32
Spectral Diffusion short time limit (no flip limit): Gaussian decay long time limit (multiple flip limit): exponential decay Grenoble 21.09.11-33
Temperature Dependence short time limit (no flip limit): long time limit (multiple flip limit): Theoretical papers: P. Hu, S.R. Hartmann, PRB 9, 1 (1974) J.L. Black, B.I. Halperin, PRB 16, 2879 (1976) P. Hu, L.R. Walker, PRB 18, 1300 (1978) R. Maynard, R. Rammal, R. Suchail, J. Phys. Paris Lett. 41, L-291 (1980) B.D. Laikhtman, PRB 31, 400 (1985) Yu.M. Galperin, V.L. Gurevich, D.A. Parshin, PRB 37, 10339 (1988) Grenoble 21.09.11-34
Echo Amplitude: Magnetic Field Dependence Tunneling systems couple to magnetic fields What is different in case of a-sio 2? Grenoble 21.09.11-35
Nuclear Quadrupole Moment is Important nuclear quadrupole moment of tunneling particle sees the electric field gradient in the two wells splitting of tunneling levels multi-level systems magnetic field causes an additional Zeeman splitting of nuclear levels Grenoble 21.09.11-36
Isotope Effect H D Glycerol H H H H C C C H OH OH OH D D D D C C C D OD OD OD hydrogen deuterium atom proof of the quadrupole model Grenoble 21.09.11-37
Evidence for a Dipole Gap in Glasses modification of density of states: dipole gap slow sweep experiment Grenoble 21.09.11-38
Memory Effect slow sweep after applying 5 MV/m for 2 h dielectric constant remembers previous dc-field Grenoble 21.09.11-39