(Fig. a) - Spectrum exhibits an inversion of the energy band edge position L6- and L6+ (transition through the zero-gap state at z = 0.65) ^*)

•          The In impurity level position is inside the conduction band (CB) for PbTe and deep inside in the valence band (VB) for SnTe ^*) on the background of VB with the high DOS, Fig. a, b

•         Width of the In impurity band increases from about 1meV in PbTe to 200 meV in SnTe due to interaction between IB and two (L and S) VB states (Fig. b) ^**)

The critical parametres Tc and H_c2(T) were determined from the condition R=0.5RN (RN - normal resistance). Tc= 4.24K, dH_c2/dT = -13.8kOe/K. The material is a typical type-II superconductor: the Ginsburg-Landau parameter is k = l/z = 75 ^*) and z(0) =(F₀/2pH_c2(0))^1/2 = 100A for H_c2(0) = 55kOe (see the next fig.).

Composition dependencies of the SC transition parameters: the critical temperature Tc (a), temperature derivative of Hc2 near Tc (b), upper critical magnetic field Hc2(0) extrapolated to T=0 (c), and DOS at the Fermi level N(0) calculated using the relation N(0)=2.84x10¹⁴|dHc2/dT|Tcr N-1 (for “dirty” superconductors) (d).  

Temperature dependencies of resistivity in (Pb_zSn_1-z)_0.84 In_0.16Te solid solutions with various Pb content z=0.5 – 0.9.

Temperature dependencies of magnetoresistivity in PbSnTe:In in the vicinity of the S-I transition

Fig.a.                                                                          Fig. b.

Temperature dependencies of magnetoresistivity (I=100mka) in (Pb_0.6Sn_0.4)_0.84In_0.16Te (Fig. a) and (Pb_0.7Sn_0.3)_0.84In_0.16Te (Fig. b) solid solutions (in the region of the S-I transition).

Magnetic field dependencies of voltage –

current characteristics in (Pb_0.6Sn_0.4)_0.84In_0.16Te solid solution at T=1.2K and T=4.2K (H=0)

Transition between  the semiconductor normal state and superconducting mesoscopic system near T = 1.7K

Temperature dependencies of magnetoresistivity in (Pb_0.7Sn_0.3)_0.84In_0.16Te solid solution at low (T=1.4K – 0.4K) temperatures.

Anomalous magnetoresistance in PbSnTe:In in the vicinity of S-I transition

Fig.a.   Z=0.7                                                                         Fig.b.   Z=0.8

Fig.c.   Z=0.9                                                                         Fig.d.  T=1.4K

IVC investigations of PbSnTe:In compounds on the insulation side of S-I transition

Nonlinear current dependencies of resistivity (a), carrent – voltage characteristics at various T (b) and magnetoresistance (c) in (Pb_0.8Sn_0.2)_0.8In_0.2Te

(z=0.7, 0.8, 0.9) (d).

SC properties of bulk and thin films PbSnTe:In materials

SC transition temperature in (Pb_zSn_1‑z)_1-xIn_xTe solid solutions vs lead content z (bulk material x=0.05, 0.16 and 0.2 and thin (d~1 mkm) films with x=0.05 and o.16).

Conclusions

• The optimal composition and In doping level allow to achieve the highest SC parameters in solid solutions based on PbSnTe:In system.

• The filling of the In impurity band located against the background of the heavy hole band is responsible for the high SC parameters in the PbSnTe:In system.

• The higher concentration of In dopant the wider region of Pb content for high SC parameters of PbSnTe:In system.

• The superconducting – insolating transition in the low temperature conductivity of varied PbSnTe:In compounds was found out.

• The anomalous magnetoresistance in the vicinity of the S – I transition consists of the negative and positive parts associated with a transition from a superconducting mesoscopic system to a semiconductor with the weak localization effect in the normal state.

• The studied material is of interest for development of SC bolometers and nanoscale devices.

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  The last update was made on November 25, 2004
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