Current-Induced Pair Breaking in Magnesium Diboride

Abstract

The transport of electrical current through a superconductor falls into three broad regimes: non-dissipative, dissipative but superconducting, and normal or non-superconducting. These regimes are demarkated by two definitions of critical current: one is the threshold current above which the superconductor enters a dissipative (resistive) state; the other is the thermodynamic threshold above which the superconductivity itself is destroyed and the superconducting order parameter vanishes. The first threshold defines the conventional critical current density Jc and the second defines the depairing (or pair-breaking) current Jd. Type II superconductors in the mixed state have quantized flux vortices, which tend to move when acted upon by the Lorentz driving force of an applied transport current. In such a mixed state the resistance vanishes only when vortices are pinned in place by defects and the applied current is below the threshold Jc required to overcome pinning and mobilize the vortices. Typically Jd >> Jc and a direct experimental measurement of Jd over the entire temperature range (0 < T < Tc) is prohibited by the enormous power dissipation densities (p ~ 10^10 -- 10^12 W/cm^3) needed to reach the normal state. In this work, intense pulsed signals were used to extend transport measurements to unprecedented power densities (p ~ 10^9 -- 10^10 W/cm^3). This together with MgB2's combination of low normal-state resistivity and high transition temperature have permitted a direct estimation of \jd over the entire temperature range. This review describes our experimental investigation of current-induced depairing in MgB2, and provides an introduction to the phenomenological theories of superconductivity and how the observations fit in their context.

Accepted for publication as a Topical Review in the Journal of Physics: Condensed Matter (Fall 2004)

References in corpus (7)

• Enhancement of the upper critical field by nonmagnetic impurities in dirty two-gap superconductors
• Unstable flux flow due to heated electrons in YBaCuO films
• Growth of superconducting MgB2 thin films via postannealing techniques
• Depairing currents in superconducting films of Nb and amorphous MoGe
• Thermal conductivity of MgB${}_2$ in the superconducting state
• The pair-breaking critical current density of magnesium diboride
• Critical flux pinning and enhanced upper-critical-field in magnesium diboride films

Cited by in corpus (17)

• Limits of the upper critical field in dirty two-gap superconductors
• Dynamics of vortex penetration, jumpwise instabilities and nonlinear surface resistance of type-II superconductors in strong rf fields
• Kinetic impedance and depairing in thin and narrow superconducting films
• Phase textures induced by dc current pairbreaking in multilayer structures and two-gap superconductors
• Vortex instability in molybdenum-germanium superconducting films
• Evaluating free flux flow in low-pinning molybdenum-germanium superconducting films
• A peak in the critical current for quantum critical superconductors
• Theory of the critical current in two-band superconductors with application to MgB2
• Achieving the depairing limit along $c$ axis in Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$ single crystals
• Multiple-q current states in a multicomponent superconducting channel
• Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion
• Dynamic pair-breaking current, critical superfluid velocity and nonlinear electromagnetic response of nonequilibrium superconductors
• Roles of intrinsic anisotropy and pi-band pairbreaking effects on critical currents in tilted c-axis MgB2 films probed by magneto-optical and transport measurements
• The ballistic acceleration of a supercurrent in a superconductor
• Thermally-activated dynamics of spontaneous perpendicular vortices tuned by parallel magnetic fields in thin superconducting films
• Evaluating Superconductors through Current Induced Depairing
• Dissipative-regime measurements as a tool for confirming and characterizing near-room-temperature superconductivity