Phase Relaxation Time Research Articles

Excess-conductivity of Nd0.1Y0.9Ba2Cu3O7−δ and Ca0.1Y0.9Ba2Cu3O7−δ superconductors: A quantitative comparison between results of aliovalent and isovalent substitutions in Y-site

The effects of Nd and Ca substitutions in the Y-sites of YBa2Cu3O7−δ (Y-123) superconductors are presented. Nd substitution reduced the critical temperature more than Ca substitution. Different models were used for the analysis of excess conductivity data, and the crossovers between different temperature regimes are discussed. Physical parameters such as phase relaxation times were obtained for both samples from this analysis. One-, two-, and three-dimensional behaviors were observed for both samples, but the exponent related to short wavelength behavior were not obtained. Two-dimensional behavior was the dominant regime for both samples.

Critical regime and suppression of the pseudo-gap in Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ superconductors via excess conductivity analyses

We have doped Zn at the Cu planar sites in Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ (y=0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) superconductors, which decrease the population of small spins of Cu atoms and most likely suppress the anti-ferromagnetically aligned spins in the inner-CuO2 planes (IP). For the observation of such effects, fluctuation induced conductivity (FIC) analyses of the above mentioned samples have been carried out using the Aslamazov–Larkin (AL) theory in the critical regime closer to the transition temperature (Tc) and the Lawrence–Doniach (LD) model closer to Tc and above. The idea behind these analyses is the fact that Cooper pair formation starts well above Tc. The influence of the Cooper-pairs on the normal electrons is determined by the Maki-Thompson (MT) model. From these analyses we have determined the coherence length along the c-axis (ξc(0)), the inter-plane coupling constant (J), the phase relaxation time of the carriers (τφ), the Fermi velocity (VF) of the carriers and the energy required to break apart the electrons pairs (Epb). Using the Ginzburg number (NG) and the Ginzburg–Landau (GL) equations, the thermodynamic critical magnetic field (Bc(0)), the lower critical field (Bc1(0)), the upper critical field (Bc2(0)), the critical current density (Jc(0)) and the penetration depth (λp.d) are also calculated. Four fluctuation regions above Tc are observed for all of the samples, namely the critical (cr), three dimensional (3D), two dimensional (2D) and zero dimensional (0D) fluctuation regions. The values of Bc(0), Bc1(0) and Jc(0) are increased while the values of E and λp.d are suppressed with increasing Zn content at Cu sites. The intersection of 2D LD, and 0D exponents determines a cross-over of 2D LD & MT contributions. Associated with the width of 3D AL/LD regimes, the crossover temperature T3D-2D is shifted to higher values with enhanced Zn doping. It is most likely that decreased density of small spins of Cu atoms induced by increased Zn doping, may suppress the spin scatterings that consequently result in higher values of T3D-2D, critical fields (Bc(0), Bc1(0)), Jc(0) and lower values of Epb and λp.d in the final compound. The decreased density of small spins of Cu atoms in the CuO2/ZnO2 planes is viewed in terms of suppression of the spin gap and, hence, the pseudo-gap in Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ (y=0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) superconductors.

Fluctuation-induced conductivity analyses of Be-doped (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ superconductors in the critical regime and beyond

We have successfully synthesized (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10−δ and (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10−δ samples and studied their excess conductivity analyses (fluctuation-induced conductivity) of resistivity data. The main objective of such analyses is to investigate the influence of Be-substitution on the superconductivity parameters at the microscopic level. The width of the 3D-2D Lawrence-Doniach regime is increased with the doping of Be at the Ca sites. The energy required to break apart the Cooper pairs is increased from 0.03 eV to 0.08 eV in Be-doped samples. Using the Ginzburg-Landau number (NG) and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are also calculated from these analyses. The values of critical fields [Bc(0) Bc1(0)], Jc(0), and phase relaxation time τϕ are increased whereas the penetration depth λp.d and κ values are suppressed with Be-doping. It is most likely that as a result of the enhancement in the density of the carriers in the (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10−δ sample, this charge density gap is suppressed, which in turn suppresses the pseudo-gap resulting into enhancement of Bc (0), Bc1(0), and Jc(0).

Excess Conductivity Analysis and the Critical Region in Be-Doped Cu0.5Tl0.5Ba2Ca1−y Be y Cu0.5Zn1.5O8−δ Superconductors

The excess conductivity analysis of as-prepared and oxygen-annealed Be-doped Cu0.5Tl0.5Ba2Ca1−yBey(Cu0.5Zn1.5)O8−δ (y=0, 0.15, 0.3, 0.45) superconducting samples is carried out in the critical regimes and beyond. Various superconducting parameters, like the zero resistance critical temperature Tc, mean field critical temperature \(T_{c}^{mf}\), onset temperature of superconductivity T∗, the crossover temperature TG of the critical and 3D fluctuations and dimensionality of fluctuations are determined. From the 3D to 2D crossover, and at the termination of 2D fluctuations, the coherence length ξc(0) along the c-axis, the coupling constant J, the phase relaxation time τφ, the Fermi velocity VF of the carriers and Fermi energy EF are calculated. Using the Ginzburg–Landau (G–L) equations in the critical regime, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0) and the critical current density Jc(0) are also calculated from these analyses. Four fluctuation regions above Tc are observed for all of the samples, namely the critical (cr), three-dimensional (3D), two-dimensional (2D) and zero-dimensional (0D) fluctuations regions. It is observed that with the increased Be content at Ca sites, ξc(0), VF and the coupling constant J are increased, which shows that the inter-planar coupling is improved by the incorporation of Be atoms at the Ca sites.

Excess conductivity of Pb-doped (Cu0.5−xPbxTl0.5)Ba2Ca2Cu3O10−δ superconductors

The excess conductivity was determined from the resistivity measurements of the as-prepared and oxygen annealed (Cu0.5−xPbxTl0.5)Ba2Ca2Cu3O10−δ (x=0, 0.15, 0.25, 0.35) samples in the temperature region well above the superconducting transition temperature. The excess conductivity data was analyzed in the light of Aslamazov–Larkin (AL) theory and its modified form given by Lawrence–Doniach (LD) model. These analyses have shown that the excess conductivity data of (Cu0.5−xPbxTl0.5)-1223 samples fits very well to the two-dimensional (2D) and three-dimensional (3D) AL equations. Moreover, at higher temperature a crossover from 2D to 0D was also observed. The width of 3D region has been increased; but, the increase was not monotonous. However, the width of 0D region has been increased up to x=0.25. The zero temperature coherence length [ξc(0)] has shown a decreasing trend with the increase of Tc(0) and Pb concentration in the charge reservoir layer (Cu0.5−xPbxTl0.5)Ba2O4−δ. The phase relaxation time [τϕ] and coupling parameter λ obtained from FIC analysis shows that the fluctuation pairs are formed both due to electron–phonon and electron–electron correlations in (Cu0.5−xPbxTl0.5)-1223 samples. The (Cu0.5−xPbxTl0.5)-1223 samples were also annealed in oxygen to change the carrier concentration in the CuO2 planes. A possibility of suppression of the spin and charge density gaps with Pb-doping is also discussed.

Excess conductivity of Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ superconductors

Oxide high-Tc superconductors (HTSC) are anisotropic in character since the charge carriers have free moment in the conducting CuO2 planes [A. L. Solov’ev and V. M. Dmitriev, Fiz. Nizk. Temp. 35, 227 (2009) [Low Temp. Phys. 35, 169 (2009)]] whereas their motion is impeded by insulating/partially insulating MBa2O4−δ (M = Y, Bi, Hg, Tl, CuTl, etc.) charge reservoir layers. In the transport process the charge carriers have to tunnel across insulating/partially insulating barriers along the c-axis and across the grain boundaries, which promote a fluctuation in the order parameter and in turn to the conductivity of the carriers. The studies of such fluctuation conductivity (FIC) may help in understanding the intrinsic mechanism of superconductivity. Here the electrical resistivity ρ(T) versus temperature data of as-prepared and oxygen post-annealed Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ (y = 0, 0.5, 1.5, 2.5) samples is studied for FIC analyses in the temperature regime well above the critical temperature; such analyses have been carried out by employing Lawrence and Doniach (LD) and Maki–Thompson (MT) models. The coherence length, inter-plane coupling, exponent, dimensionality of fluctuations and the phase relaxation time of the carriers are determined from such analyses. It is observed that the crossover temperature associated with two distinct exponents fits very well with the two-dimensional (2D) and three-dimensional (3D) LD equations. The crossover temperature T0 is shifted to higher temperatures with enhanced Zn doping. The 3D LD region is shifted to higher temperature with the increased Zn doping. We have elucidated from these analyses that lower Tl content in the final compound may increase the charge carrier’s doping efficiency of MBa2O4−δ charge reservoir layer, resulting into an increase in the coherence length along the c-axis and superconductivity parameters. A small decrease in the coherence length along the c-axis ξc(0) is observed in the samples with Zn doping of y = 1.5 whereas ξc(0) increases in the samples y = 0.5, 2.5. In comparison with as-prepared samples, the ξc(0) decreases after post-annealing in oxygen atmosphere. It is most likely that a decrease in the density of charge carrier’s is promoted by oxygen diffusion in the unit cell may suppress the ξc(0). The increase oxygen diffusion is evidenced from the softening of phonon modes after post-annealing in oxygen atmosphere. The decreased population of small spins of Cu atoms induced by doping of Zn is viewed in the terms of suppression of spin gap and hence the pseudo-gap in Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ (y = 0, 0.5, 1.5, 2.5) samples.

Magnetoresistance effects and phase coherent transport phenomena in a magnetic nonplanar two-dimensional hole system

Phase coherent transport phenomena are studied in a magnetic, two-dimensional hole system confined in a strained InAs quantum-well structure. At low magnetic fields we observe a well pronounced weak antilocalization signature, demonstrating that magnetic ions in proximity to the itinerant holes preserve phase coherent transport, although magnetic effects like the anomalous and planar Hall effects are present at low temperatures. From fits to the conductivity correction, spin and phase relaxation times are extracted in a large temperature range from 200 mK to 16 K. From the dependency of the spin relaxation time on temperature and in-plane magnetic fields, we conclude that the Dyakonov-Perel mechanism is the dominant spin relaxation mechanism. The metamorphic growth of the heterostructure causes a nonplanar quantum well that enables the formation of magnetic barriers in the presence of a parallel applied magnetic field. Transport through these magnetic barriers causes a positive magnetoresistance superimposed on the weak antilocalization signal.

Suppressed phonon density and Para conductivity of Cd doped Cu 0.5Tl 0.5Ba 2Ca 3Cu 4− yCd yO 12− δ ( y = 0, 0.25, 0.5, 0.75) superconductors

The fluctuation-induced conductivity (FIC) above critical temperature ( T c) was measured in Cd doped (Cu 0.5Tl 0.5)Ba 2Ca 3(Cu 4− y Cd y )O 12− δ ( y = 0, 0.25, 0.5, 0.75) as prepared and oxygen post-annealed superconductors using the Aslamazov–Larkin (AL) and Maki–Thompson (MT) models. From this FIC analysis the coherence length ξ c(0) along the c-axis, inter-plane coupling, dimensionality of fluctuations, the phase relaxation time τ φ and Fermi velocity V F of the carriers were calculated. All of the samples have shown 3D, 2D and 0D fluctuations above T c. T*, the temperature at which the resistivity curve deviates from the linear behavior, is shifted to lower temperatures with increasing Cd concentration. Width of the transition Δ T is shrunked with the enhanced Cd doping. The crossover temperature T o is shifted to lower temperature values with increased Cd contents. Most likely these effects may be arising due to the replacement of Cu atoms by the heavier Cd atoms thereby producing inharmonic oscillations and causes suppression of the density of phonons which in turn suppress T* and Δ T.

Nonselective excitation of pulsed ELDOR using multi-frequency microwaves

The use of a polychromatic microwave pulse to expand the pumping bandwidth in pulsed electron–electron double resonance (PELDOR) was investigated. The pumping pulse was applied in resonance with the broad (∼100 mT) electron paramagnetic resonance (EPR) signal of the manganese cluster of photosystem II in the S 2 state. The observation pulses were in resonance with the narrow EPR signal of the tyrosine radical, Y D . It was found that in the case of the polychromatic pumping pulse containing five harmonics with the microwave frequencies between 8.5 and 10.5 GHz the PELDOR effect corresponding to the dipole interaction between the Mn cluster and Y D was about 2.9 times larger than that achieved with a monochromatic pulse. In addition to the dipolar modulation, the nuclear modulation effects were observed. The effects could be suppressed by averaging the PELDOR trace over the time interval between the observation microwave pulses. The polychromatic excitation technique described will be useful for improving the PELDOR sensitivity in the measurements of long distances in biological samples, where the pair consists of a radical with a narrow EPR spectrum and slow phase relaxation, and a metal center that has a broad EPR spectrum and a short phase relaxation time.

Excess-conductivity of (Bi0.5Tl0.5)Ba2Ca2Cu3O10-δ superconductors

Excess conductivity analysis of electrical resistivity ρ(T) versus temperature data is carried out for as-prepared, Nitrogen (N2) and Oxygen (O2) annealed (Bi0.5Tl0.5)Ba2Ca2Cu3O10-δ samples. Such analyses have been done following the lawrence doniach model. Two cross-over temperatures have been observed, one for transformation from 0D to 2D at higher temperature and the other for 2D to 3D closer to the transition temperature. The widths of 3D AL regime remains unchanged after post-annealing in N2 and O2 atmospheres whereas that of 2D AL regimes in N2 and O2 post-annealed samples is significantly decreased. The width of 3D AL regimes remains unaltered after post-annealing in N2 and O2 atmosphere, however, the width of 2D AL regimes is significantly decreased after annealing experiments. The shrinkage of 2D AL region to lower temperature after annealing is most likely consequence of readjustment of carrier’s density in the conducting CuO2 planes. The coherence length along the c-axis (ξc) is determined at the cross-over To of 2D to 3D conductivity. In as prepared samples ξc is around 1.18 Å, which is marginally increased to 1.22 Å in the samples annealed in N2 atmosphere and to 1.27 Å in O2 annealed samples. The coherence length ξc and inter-plane coupling J are enhanced with post-annealing in nitrogen and oxygen atmosphere. The phase relaxation time and Fermi-velocity of the carrier are significantly enhanced after post-annealing in oxygen. The optimized density of the carriers suppresses overall coupling energy in oxygen post-annealed samples and the lower value of it suggests the dominance of electron-electron correlation effects in the conductivity mechanism of oxygen post-annealed Bi0.5Tl0.5Ba2Ca2Cu3O10-δ samples. Our FIC data suggests a significant suppression of spin and charged density gaps in oxygen post-annealed samples.

Diameter dependence of phase relaxation time and third-order nonlinear susceptibilities in semiconducting single-walled carbon nanotubes

Diameter dependence of the phase relaxation time T2 in semiconducting single-walled carbon nanotubes was measured using a two-beam time-resolved degenerate four-wave mixing method. The T2 value increases with increasing tube diameter. This experimental trend can be understood by the diameter dependence of exciton-phonon interaction. We also discuss the origin of diameter dependence of third-order nonlinearity connected with relaxation times.

Magnetic Field Dependence of Quadrupolar Splitting and Nuclear Spin Coherence Time in a Strained (110) GaAs Quantum Well

We investigated the magnetic field dependence of quadrupolar splitting and phase relaxation time of nuclear spins in an n-GaAs/AlGaAs (110) quantum well (QW) by optically detected nuclear magnetic resonance (NMR). The NMR spectra show large quadrupolar splitting induced by an internal field gradient in the QW epilayer. At lower magnetic fields, the quadrupolar splitting become much enhanced, resulting in the appearance of the second order magnetic field dependence of the quadrupole interaction in the NMR spectra. It is also shown that the intrinsic coherence time and the effective coherence time for resonant transitions become shorter as a result that the energy splitting between the two levels becomes small and incoherent transition is occurred by irradiation of an rf magnetic field.

Thermal Relaxation and Heat Transport in the Spin Ice Material Dy2Ti2O7

The thermal properties of single crystalline Dy2Ti2O7 have been studied in a temperature range from 0.3 K to 30 K and magnetic fields applied along [110] direction up to 1.5 T. Based on a thermodynamic field theory various heat relaxation and thermal transport measurements were analysed. So we were able to present not only the heat capacity of Dy2Ti2O7 in the whole temperature and magnetic field range, but also the different contributions of the magnetic excitations and their corresponding relaxation times in the spin ice phase. In addition, the thermal conductivity and the shortest relaxation time were determined by thermodynamic analysis of steady state heat transport measurements. Finally, we were able to reproduce the temperature profiles recorded in heat pulse experiments on the basis of the thermodynamic field theory using the previously determined heat capacity and thermal conductivity data without additional parameters. Thus, the thermodynamic field theory has been proved to be thermodynamically consistent in describing three thermal transport experiments on different time scales. The observed temperature and field dependencies of heat capacity contributions and relaxation times indicate the magnetic excitations in the spin ice material Dy2Ti2O7 as thermally activated monopole-antimonopole defects.

Characterization of crystallisation processes with electrical impedance spectroscopy

The surfaces of crystalline particles are often charged and therefore crystals have an electrical double layer associated with their surfaces when, for example, suspended in an aqueous medium. Under the influence of an external electric field, an electrical dipole moment can be induced due to polarization of the electrical double layer. The complex impedance, conductivity, relaxation time and phase shift caused by the polarization are all related to particle characteristics, e.g. the size, polymorph and concentration. The method of electrical impedance spectroscopy (EIS) provides, potentially, a capability for characterizing the particles in colloidal suspensions. Here some preliminary observations of physical-chemistry fundamentals relating to the use of electrical impedance spectroscopy, potentially, for particle sizing in crystallisation processes are reported. Firstly, the effects of l-glutamic acid (LGA) solids concentration, solute concentration and temperature on the measured EIS spectra were studied. The results show that the effects of solid LGA concentration and solute concentration on the relaxation frequency and phase angle are very small. Secondly, the temperature effect was analysed. By deducting the contribution due to the changes in concentration and temperature from the total change in relaxation frequency, the experimental observations, although preliminary in nature, suggest that the crystal size can be related directly to relaxation frequency (in this study, the shape of LGA crystals is assumed to be spherical so the crystal size means the diameter of the sphere). The experimental observations can be explained with either static polarization models or particle vibration models. On-line measurement of electrical impedance spectra associated with LGA nucleation–growth processes are presented. The information content of the complex electrical impedance, phase angle shift and relaxation times of the crystal suspensions during a crystallisation process is assessed. The results show that during nucleation the imaginary part of the electrical-impedance response changes significantly and the relaxation frequency decreases during the growth of crystals. The longer-term objective is to develop a new spectroscopic measurement method and further, a spectroscopic tomography technique for on-line measurement of the spatial distribution of particle size in particle suspensions in liquid media.

Fluctuation-induced conductivity and dimensionality in the new Y-based Y3Ba5Cu8O18- x superconductor

The fluctuation conductivity measurement on the new Y-based Y3Ba5Cu8O18-x superconductor is presented. The dimensional crossovers between different temperature regimes were analyzed with Aslamazov-Larkin (AL) theory and a good quantitative agreement was achieved for the experimental data. For our data, the mean field regime is dominated by 2D AL fluctuations. Our results reveal the occurrence of critical fluctuation regime in consistent with the prediction of the full dynamic 3D XY model. We found the dynamical critical exponent to be z = 3.4 for our data. We analyzed also the excess conductivity data by Hikami-Larkin theory and estimated the phase relaxation time.

Study of overheating effects in SiGe‐based p‐type heterostructures: Methods of the hole temperature determination

AbstractThe effect of charge carrier overheating is studied in the p‐type Si/Si0.87Ge0.13/Si heterostructure. The hole temperature Th can be calculated using three different methods: From a comparison of the changes in the amplitude of the Shubnikov‐de Haas oscillations under the influences of temperature and current, from a comparison of the change of phase relaxation time in the weak localization effect obtained at different temperatures and minimum current and at a given temperature but at different values of current, and from a comparison of the temperature and current dependence of the sample resistance. The temperature dependences values of Th obtained using three different methods were identical and exhibit transition of the two‐dimensional system under study from the regime of “partial inelasticity” to that of small angle scattering at temperature lowering.Die Überhitzung der Ladungsträger wurde in p‐Typ Si/Si 0.87 Ge 0.13/Si Heterostrukturen untersucht. Die Lochtemperatur Th kann mit drei unterschiedlichen Methoden berechnet werden: Durch den Vergleich der Amplitudenänderungen der Shubnikov‐de Haas Oszillationen unter den Einflüssen von Temperatur und Stromstärke, durch den Vergleich der Änderung der Phasenrelaxationszeit im schwachen Lokalisierungseffekt bei unterschiedlichen Temperaturen, minimaler Stromstärke und bei gegebener Temperatur und unterschiedlicher Stromstärke, sowie durch den Vergleich die Abhängigkeit des Probenwiderstandes von Temperatur‐ und Stromstärke. Die Werte der Temperaturabhängigkeit von Th, die nach drei verschiedenen Methoden erhalten wurden, waren identisch und zeigten einen Übergang des betrachteten zweidimensionalen Systems vom Bereich der “partiellen Inelastizität” zur Kleinwinkelstreuung bei tieferer Temperatur.

Decoherence by electromagnetic fluctuations in double-quantum-dot charge qubits

We discuss decoherence due to electromagnetic fluctuations in charge qubits formed by two lateral quantum dots. We use an effective circuit model to evaluate correlations of voltage fluctuations in the qubit setup. These correlations allows us to estimate energy (T1) and phase (T2) relaxation times of the the qubit system. Our theoretical estimate of the quality factor due to dephasing by electromagnetic fluctuations yields values much higher than those found in recent experiments, indicating that other sources of decoherence play a dominant role.

Impossibility of faithfully storing single photons with the three-pulse photon echo

The three-pulse photon echo is a well-known technique to store intense light pulses in an inhomogeneously broadened atomic ensemble. This protocol is attractive because it is relatively simple and it is well suited for the storage of multiple temporal modes. Furthermore, it offers very long storage times, greater than the phase relaxation time. Here, we consider the three-pulse photon echo in both two- and three-level systems as a potential technique for the storage of light at the single-photon level. By explicit calculations, we show that the ratio between the echo signal corresponding to a single-photon input and the noise is smaller than one. This severely limits the achievable fidelity of the quantum state storage, making the three-pulse photon echo unsuitable for single-photon quantum memory.

Electronic and Vibrational Coherence Dynamics in a Cyanine Dye Studied Using a Few‐Cycle Pulsed Laser

We report the relaxation times of electronic and vibrational coherence in the cyanine dye 1,1',3,3,3',3'-hexamethyl-4,4',5,5'-dibenzo-2,2'-indotricarbocyanine, measured using a 7.1 fs pulsed laser. The vibrational phase relaxation times are found to be between 380 and 680 fs in the ground and lowest excited singlet states. The vibrational dephasing times of the 294, 446, and 736 cm(-1) modes are relatively long among the six modes associated with excited-state wave packets. The slower relaxations are explained in terms of a coupled triplet of vibrational modes, which preserves coherence by forming a tightly bound group to satisfy the condition of circa conservation of vibrational energy. Using data from the negative-time range (i.e., when the probe pulse precedes the pump pulse), the electronic phase relaxation time is found to be 31+/-1 fs. The dynamic vibrational mode in the excited state (1171 cm(-1)), detected in the positive-time range, is also studied from the negative-time traces under the same experimental conditions.

Quantum Interference Effects in p-Si1−x Ge x Quantum Wells

Quantum interference effects, such as weak localization and electron- electron interaction (EEI), have been investigated in magnetic fields up to 11 T for hole gases in a set of Si1−xGex quantum wells with 0.13 <x <0.95. The temperature dependence of the hole phase relaxation time has been extracted from the magneto- resistance between 35 mK and 10 K. The spin-orbit effects that can be described within the Rashba model were observed in low magnetic fields. A quadratic negative magneto-resistance was observed in strong magnetic fields, due to the EEI effect. The hole-phonon scattering time was determined from hole overheating in a strong magnetic field.