Undergraduate experiment in superconductor point-contact spectroscopy with a Nb/Au junction

Janson, Lucas; Klein, M.; Lewis, Heather; Lucas, A. A.; Marantan, Andrew; Luna, Katherine

doi:10.1119/1.3660665

Cited by 13 publications

(12 citation statements)

References 24 publications

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“…The value of Δ i as well as quality of the junction formed by Au electrodes and the TI were determined from fitting the conductance of Sample A with the modified BTK model at 18 K, as shown in Fig. 2 c. The normalized conductance, G, at low temperature can be written as 38 , 39 : where and are the probabilities of Andreev and normal reflections of electrons at the interface, respectively. The terms and can written in terms of three parameters: the superconducting gap Δ, the quasiparticle decay rate Γ, and the interface barrier Z 40 .…”

Section: Resultsmentioning

confidence: 99%

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

Kiphart

Harkavyi

Balin

et al. 2021

Sci Rep

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We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced gap. Results of our experiments have shown that Raman spectroscopy is a complementary technique to classic charge transport experiments and is a powerful tool for investigation of the proximity-induced superconductivity in the Bi2Te3.

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Section: Resultsmentioning

confidence: 99%

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

Kiphart

Harkavyi

Balin

et al. 2021

Sci Rep

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“…Perhaps, the most common method of making a point contact involves slowly moving a sharp metallic tip towards the surface of a sample until a light "ohmic" contact is established. This method is popularly known as the "needle-anvil" [29][30][31] method. Here, the tip can be moved towards or away from the sample surface using either a mechanical differential screw arrangement or piezo driven mechanism(See Fig1(a)).…”

Section: A Fabrication Of Point Contactsmentioning

confidence: 99%

Tip-induced Superconductivity

Howlader,

Sheet

2020

Preprint

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It is widely believed that topological superconductivity, a hitherto elusive phase of quantum matter, can be achieved by inducing superconductivity in topological materials. In search of such topological superconductors, certain topological insulators (like, Bi 2 Se 3 ) were successfully turned into superconductors by metal-ion (Cu, Pd, Sr, Nb etc. ) intercalation. Superconductivity could be induced in topological materials through applying pressure as well. for example, a pressureinduced superconducting phase was found in the topological insulator Bi 2 Se 3 . However, in all such cases, no conclusive signature of topological superconductivity was found. In this review, we will discuss about another novel way of inducing superconductivity in a non-superconducting topological material -by creating a mesoscopic interface on the material with a non-superconducting, normal metallic tip where the mesoscopic interface becomes superconducting. Such a phase is now known as a tip-induced superconducting (TISC) phase. This was first seen in 2014 on Cd 3 As 2 at IISER Mohali, India. Following that, a large number of other topological materials were shown to display TISC. Since the TISC phase emerges only at a confined region under a mesoscopic point contact, traditional bulk tools for characterizing superconductivity cannot be employed to detect/confirm such a phase. On the other hand, such a point contact geometry is ideal for probing the possible existence of a temperature and magnetic field dependent superconducting energy gap and a temperature and magnetic field dependent critical current. We will review the details of the experimental signatures that can be used to prove the existence of superconductivity even when the "text-book" tests for detecting superconductivity cannot be performed. Then, we will review different systems where a TISC phase could be realized.

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“…where E is the quasiparticle energy, and Γ is its scattering rate [19,20,21]. The resulting theory has the form identical to the BTK theory but with the normalized superconducting quasiparticle DOS given by the so-called Dynes…”

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confidence: 99%

“…Two characteristic fits to the conductance spectra (dI/dV vs T ) at different temperatures are displayed in Fig. 3, panels A and C. For comparison we also show the fits using a phenomenological approach [19,20,21] based on the Dynes broadening parameter (panels B and D in Fig. 3).…”

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confidence: 99%

“…Superconducting energy gap ∆(T ) of Cd2Re2O7 (square symbols) obtained by fitting the experimental data of Fig. 2 for the normalized conductance at different temperatures using (a) the generalized BTK theory presented in this work and (b) the phenomenological approach [19,20,21]. The circles in (a) give the values of the imaginary part of the gap at the gap edge obtained in the fits while the circles in (b) give the Dynes broadening parameter Γ(T ).The thick lines give the BCS temperature dependence of the gap.…”

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The effect of quasiparticle self-energy on Cd₂Re₂O₇ superconductor

et al. 2015

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The magnitude and the temperature dependence of the superconducting order parameter Δ(T) of single crystals of Cd2Re2O7 (Tc = 1.02 K) was measured using point-contact spectroscopy. To fit the conductance spectra and to extract the order parameter at different temperatures we generalized the Blonder–Tinkham–Klapwijk theory by including the self-energy of the quasiparticles into the Bogoliubov equations. This modification enabled excellent fits of the conductance spectra. Δ(T) increases steeply below the superconducting transition temperature of 1.02 K and levels off below ∼0.8 K at a value of 0.22(1) meV, ≈40% larger than the BCS value. Our results indicate the presence of a strong electron–phonon interaction and an enhanced quasiparticle damping and may be related to a possible phase transition within the superconducting region at ∼0.8 K.

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Undergraduate experiment in superconductor point-contact spectroscopy with a Nb/Au junction

Cited by 13 publications

References 24 publications

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

Tip-induced Superconductivity

The effect of quasiparticle self-energy on Cd₂Re₂O₇ superconductor

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Undergraduate experiment in superconductor point-contact spectroscopy with a Nb/Au junction

Cited by 13 publications

References 24 publications

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

Tip-induced Superconductivity

The effect of quasiparticle self-energy on Cd2Re2O7 superconductor

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The effect of quasiparticle self-energy on Cd₂Re₂O₇ superconductor