Two-stage magnetic-field-tuned superconductor–insulator transition in underdoped La2−xSrxCuO4

Abstract

In the underdoped pseudogap regime of cuprate superconductors, the normal state is commonly probed by applying a magnetic field (H). However, the nature of the H-induced resistive state has been the subject of a long-term debate, and clear evidence for a zero-temperature (T = 0) H-tuned superconductor-insulator transition (SIT) has proved elusive. Here we report magnetoresistance measurements in underdoped La 2−x Sr x CuO 4 , providing striking evidence for quantum critical behavior of the resistivity -the signature of a H-driven SIT. The transition is not direct: it is accompanied by the emergence of an intermediate state, which is a superconductor only at T = 0. Our finding of a two-stage H-driven SIT goes beyond the conventional scenario in which a single quantum critical point separates the superconductor and the insulator in the presence of a perpendicular H. Similar two-stage H-driven SIT, in which both disorder and quantum phase fluctuations play an important role, may also be expected in other copper-oxide high-temperature superconductors.The SIT is an example of a quantum phase transition (QPT): a continuous phase transition that occurs at T = 0, controlled by some parameter of the Hamiltonian of the system, such as doping or the external magnetic field 1 . A QPT can affect the behavior of the system up to surprisingly high temperatures. In fact, many unusual properties of various strongly correlated materials have been attributed to the proximity of quantum critical points (QCPs). An experimental signature of a QPT at nonzero T is the observation of scaling behavior with relevant parameters in describing the data. Although the SIT has been studied extensively 2 , even in conventional superconductors many questions remain about the perpendicular-field-driven SIT in two-dimensional (2D) or quasi-2D systems 3 . In high-T c cuprates (T c -transition temperature), which have a quasi-2D nature, early magnetoresistance (MR) experiments showed the suppression of superconductivity with high H, revealing the insulating behavior 4-6 and hinting at an underlying H-field-tuned SIT 7 . However,

Growth and Electronic Transport Property of Layered BiOCl Microplates

“…Our observation shows similar behavior of SI transition in ultrathin fi lms of bismuth, [ 23 ] superconducting LaTiO 3 /SrTiO 3 interfaces, [ 24,25 ] and underdoped La 2-x Sr x CuO 4 (LSCO), [26][27][28] where there is a critical magnetic fi eld that separates the superconducting state from the insulating state. To see if the "resistance drop" is representative of superconductivity found in BiOCl MP, we also measured the magnetoresistance of the sample (Figure 4 b) and ρ as a function of the excitation current I (Figure 4 c) at different temperatures.…”

Spin susceptibility of charge-ordered YBa 2 Cu 3 O y across the upper critical field

“…We can only conjecture that disorder, which is present even in the best YBCO single crystals [37], plays a role. In particular, for two-dimensional systems in the presence of disorder, it has been shown that rare regions with anomalously high H c2 values become Josephsoncoupled at very low T [38][39][40][41]. This gives rises to two stages in the superconducting-to-normal transitions measured by resistivity vs. field [38][39][40][41].…”

Ising Superconductivity and Quantum Phase Transition in Macro-Size Monolayer NbSe2

“…In previous reports on SITs and SMTs, the magnetic resistance isotherms cross in one or two points, which are considered as quantum criticality. [14][15][16][17][18][19][20] However, in recent work on 2D superconducting Ga films 22 , the similar continuous line of SMT "critical" points and the dynamical critical exponent divergence were detected, which experimentally revealed quantum Griffiths singularity of SMTs in Ga films. 7,21,22 We then analyze our data referring to the finite size analysis method 22 (See supplemental information for details).…”

“…[14][15][16][17][18][19][20] We note that the high critical magnetic field in low temperature regime has been observed in heavy Fermion superconductors 31 and organic superconductors 32 . The mechanism was interpreted as Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state 33 .…”