Experimental evidence for a first-order vortex-lattice-melting transition in untwinned, single crystalYBa2Cu3

Current-driven vortex dynamics in untwinned superconducting single crystals

“…We note that the expression lim J J vb [ρ(T , J )] = ρ 0 (T ) holds according to equation (1), and that ρ 0 (T ) has a temperature dependence that is similar to but much weaker than ρ(T ), as shown in figure 3(a). Furthermore, the characteristic current density J vb (T ) illustrated in figure 3(b) shows a distinct peak at the temperature where a minimum in ρ(T ) occurs.…”

“…Assuming that the exponent µ is constant for given H and θ , we apply equation (1) to our data by using the fitting parameters µ, ρ 0 (T ) and J vb (T ), and find that the resistivity agrees well with the collective flux-creep model. We note that µ > 0 yields a vanishing resistivity in the small-current limit.…”

“…In the weak-pinning limit, measurements of thermodynamic quantities such as magnetization and heat capacity have confirmed the existence of a first-order melting transition in both Bi 2 Sr 2 CaCu 2 O x [9] and untwinned YBa 2 Cu 3 O 7 single crystals [10], while the resistive hysteresis observed in untwinned YBa 2 Cu 3 O 7 single crystals below the first-order vortexsolid melting transition temperature T M [1][2][3] has been attributed to the current-driven non-equilibrium effects below the thermodynamic transition [3]. Another current-induced phenomenon in weak-pinning systems is the 'peak effect', which refers to a peak feature in the critical current density (J c ) as a function of the temperature or magnetic field [17][18][19][20][21].…”

“…Recent experimental observations of novel vortex transport properties in various weakpinning type-II superconductors [1][2][3][4][5][6][7][8][9][10] have kindled renewed interest in the effects of static disorder on the thermodynamic vortex phases and phase transitions [11][12][13][14][15][16]. In the weak-pinning limit, measurements of thermodynamic quantities such as magnetization and heat capacity have confirmed the existence of a first-order melting transition in both Bi 2 Sr 2 CaCu 2 O x [9] and untwinned YBa 2 Cu 3 O 7 single crystals [10], while the resistive hysteresis observed in untwinned YBa 2 Cu 3 O 7 single crystals below the first-order vortexsolid melting transition temperature T M [1][2][3] has been attributed to the current-driven non-equilibrium effects below the thermodynamic transition [3].…”

Tearing transition and plastic flow in superconducting thin films

“…In particular, much experimental and theoretical effort has been devoted to characterizing the phase diagram of type II superconductors [4]. Depending on the value of the magnetic field H, temperature T , and sample preparation, vortices can either form a crystal [5], which at higher temperatures melts into a liquid [6,7,8,9], or, due to quenched disorder, they can be found in more complex phases, such as the vortex glass [10], the Bose glass [11] or the Bragg glass [12,13]. Of special importance is the non-equilibrium response of vortex matter to the flow of an external current [14,15], because the dissipative motion of the vortices induces an undesirable macroscopic resistance.…”