Ultra low noise YBa2Cu3O7−δ nano superconducting quantum interference devices implementing nanowires

Abstract

We present results on ultra low noise YBa 2 Cu 3 O 7−δ nano Superconducting QUantum Interference Devices (nanoSQUIDs). To realize such devices, we implemented high quality YBCO nanowires, working as weak links between two electrodes. We observe critical current modulation as a function of an externally applied magnetic field in the full temperature range below the transition temperature T C . The white flux noise below 1 µΦ 0 / √ Hz at T = 8 K makes our nanoSQUIDs very attractive for the detection of small spin systems.

Asymmetric nanowire SQUID: Linear current-phase relation, stochastic switching, and symmetries

“…Nanowire networks [12] and loops [13][14][15][16][17][18][19][20] are qualitatively distinct from conventional Josephson junction and SQUIDS due to the linear nature of the nanowire CPR [13]. In contrast, conventional Josephson junctions obey a sinusoidal CPR.…”

“…We also observe that the general shape of the I C (B) curve is made of linear segments rather than being sinusoidal. At temperatures much lower than T C , a linear CPR (and therefore a linear relationship between critical current and field) is both expected [2,[26][27][28][29] and has been observed experimentally [13,15,[22][23][24]. Advanced computational simulations based on Ginzburg-Landau theory, which is known to be valid at temperatures near the critical temperature T C [30], have been used to simulate the critical current versus field dependence of nanowire loops previously [22,24,25].…”

Sample Preparation for Inorganic Trace Element Analysis

“…Still, the fabrication of YBCO cJJs with 50 nm × 50 nm cross-section and 100 − 200 nm length has been reported recently 101 . These JJs exhibit large I c of a few mA at 300 mK.…”

Hot spot formation in electron-doped PCCO nanobridges

“…From this dependence we extract the critical current modulation depth I C (T ) = I max C (T ) − I min C (T ), which allows one to calculate the screening factor of the SQUID β expt. [29], assuming the Likharev-Yakobson expression for the current phase relation of the nanowire [30][31][32]. Furthermore, the screening factor can be expressed as…”

“…To extract the value of the London penetration depth, following Ref. [29], we have numerically calculated L loop at each temperature by solving the Maxwell and London equations describing the Meissner state on our nanoSQUID geometry, and assuming that the temperature dependence is given by the two-fluid model for the London penetration depth λ L = λ 0…”