Coherent generation of phonon-polaritons in Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Sr<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>CaCu<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow

Katterwe, Sven-Olof; Motzkau, Holger; Rydh, Andreas; Krasnov, Vladimir M.

doi:10.1103/physrevb.83.100510

Cited by 21 publications

(32 citation statements)

References 30 publications

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“…This is also a surface phenomenon, but in case of layered cuprates, which represent stacks of metallic CuO planes sandwiched between polar-insulating layers [37], electrostatic charging of insulating layers may in principle lead to the bulk persistent electrostatic field-effect.…”

Section: B Electric Field Effectsmentioning

confidence: 99%

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Persistent electrical doping of Bi2Sr2CaCu2O
Motzkau
¹
,
Jacobs
²
,
Katterwe
³

et al. 2012
Phys. Rev. B
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Application of a significantly large bias voltage to small Bi 2 Sr 2 CaCu 2 O 8+x mesa structures leads to persistent doping of the mesas. Here we employ this effect for analysis of the doping dependence of the electronic spectra of Bi-2212 single crystals by means of intrinsic tunneling spectroscopy. We are able to controllably and reversibly change the doping state of the same single crystal from underdoped to overdoped state, without changing its chemical composition. It is observed that such physical doping is affecting superconductivity in Bi-2212 similar to chemical doping by oxygen impurities: with overdoping the critical temperature and the superconducting gap decrease, with underdoping the c-axis critical current rapidly decreases due to progressively more incoherent interlayer tunneling and the pseudogap rapidly increases, indicative for the presence of the critical doping point. We distinguish two main mechanisms of persistent electric doping: (i) even in voltage contribution, attributed to a charge transfer effect, and (ii) odd in voltage contribution, attributed to reordering of oxygen impurities.

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Section: B Electric Field Effectsmentioning

confidence: 99%

“…The Bi-2212 compound has a layered structure with metallic CuO planes sandwiched between polar insulator BiO layers [37]. In this case the electrostatic charging will take place in BiO layers, which may affect the doping state of the neighboring CuO planes via the electrostatic field-effect.…”

Section: A Charge Transfer and Electrostatic Charge Trappingmentioning

confidence: 99%

Persistent electrical doping of Bi2Sr2CaCu2O
Motzkau
¹
,
Jacobs
²
,
Katterwe
³

et al. 2012
Phys. Rev. B
Self Cite
13
1
10
0
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show abstract

“…5 (c). The occurrence of photon [62] or phonon [63] emission upon inelastic tunneling is a well known phenomenon. To check the presence of the emission, we employed another junction on the same chip as a radiation detector.…”

Section: B Fowler-nordheim Tunneling Into the Conduction Band Of Thementioning

confidence: 99%

High bias anomaly in YBa2Cu3O7−x/LaMnO
Golod
¹
,
Rydh
²
,
Krasnov
³

et al. 2013
Phys. Rev. B
28
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29
0
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High bias anomaly in YBa 2 Cu 3 O 7 /LaMnO 3+δ /YBa 2 Cu 3 O 7 Superconductor/Ferromagnetic Insulator/Superconductor junctions: Evidence for a long-range superconducting proximity effect through the conduction band of a ferromagnetic insulator. We study the perpendicular transport characteristics of small superconductor/ ferromagnetic insulator/ superconductor (YBa2Cu3O7−x/ LaMnO 3+δ / YBa2Cu3O7−x) tunnel junctions. At a large bias voltage V ∼ 1 V we observe a step-like onset of excess current that occurs below the superconducting transition temperature T < Tc and is easily suppressed by a magnetic field. The phenomenon is attributed to a novel type of the superconducting proximity effect of non-equilibrium electrons injected into the conduction band of the ferromagnetic insulator via a Fowler-Nordheim tunneling process. The occurrence of a strongly non-equilibrium population is confirmed by the detection of photon emission at large bias voltage. Since the conduction band in our ferromagnetic insulator is strongly spin polarized, the long-range (20 nm) of the observed proximity effect provides evidence for an unconventional spin-triplet superconducting state. I. INTRODUCTIONThe manganite perovskite La 2−x (Ca,Sr) x MnO 3 exhibits a rich phase diagram of unusual electronic and magnetic properties. Most prominent is the so-called colossal magneto-resistance (CMR) effect which occurs at 0.15 < x < 0.5 in the context of a transition from a paramagnetic and insulating or poorly conducting state to a ferromagnetic and half metallic state [1,2]. At somewhat lower doping at 0.1 < x < 0.15, the corresponding transition leads into a ferromagnetic insulating (FI) state which is a consequence of charge localization below the spin-polaron mobility edge and orbital ordering at low T [3][4][5][6]. This FI state can also be achieved in off stoichiometric LaMnO 3+δ in which the hole doping is due to La or Mn vacancies. While half-metallic manganites are considered as promising spin-polarizers [7], the FI manganite can be an ideal spin-filter material for use in tunnel barriers with low leakage currents. Efficient spin-filters are on demand for spintronic applications [8]. Spin polarization depends on many parameters including the density of states (DOS) of electronic bands [7,[9][10][11][12], orbital hybridization and various material issues at interfaces and on the bias voltage [13]. Metallic ferromagnets provide only modest spin polarization because both majority (↑) and minority (↓) spin bands are crossing the Fermi level E F [14]. This problem is obviated in insulating and halfmetallic ferromagnets with separated majority and minority bands at E F , which, therefore, can facilitate an almost complete spin-polarization [8,[13][14][15].The antagonism between superconductivity (S) and ferromagnetism (F) leads to a variety of novel effects in hybrid S/F heterostructures [16,17], such as the stabilization of unconventional spin-triplet superconductivity [17,18], or the realization of π-Josephson junctions [19], that are interest...

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“…2 (a) of differential conductance dI/dV vs voltage per junction for an overdoped Bi(Pb)-2212 mesa. It is seen that in overdoped crystals the sub-gap conductance is dominated by strong phonon resonances [27][28][29], which appear at temperature-independent voltages. Presence of phonon resonances makes it difficult to analyze the subharmonic gap structure.…”

mentioning

confidence: 99%

Observation of a subharmonic gap singularity in interlayer tunneling characteristics ofBi2Sr2CaCu2O8+δ

Krasnov

2016

Phys. Rev. B

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A subharmonic structure in Josephson junctions appears due to Andreev reflections within the junction. Here we report on experimental observation of a subharmonic half-gap singularity in interlayer tunneling characteristics of a layered high temperature superconductor Bi2Sr2CaCu2O 8+δ . The singularity is most pronounced in optimally doped crystals and vanishes with decreasing doping. It indicates existence of non-vanishing electronic density of states and certain metallic properties in the intermediate BiO layers, which grows stronger with increasing doping. This provides an additional coherent interlayer transport channel and can explain a gradual transition from an incoherent quasi-two-dimensional c-axis transport in underdoped to a coherent metallic transport in overdoped cuprates. Furthermore, due to a very small sub-gap current, the singularity allows unambiguous extraction of the superconducting gap, without distortion by self-heating. The mechanism of interlayer (c-axis) transport in cuprate high temperature superconductors remains an actively debated subject. A qualitative difference between metallic in-plane and non-metallic out-of-plane resistivities [1] is a strong indication for predominantly incoherent nature of c-axis transport, which is achieved by interlayer hopping or tunneling [2][3][4][5][6][7]. The tunneling nature of c-axis transport leads to appearance of the intrinsic Josephson effect between CuO 2 planes in layered Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) cuprates at temperatures below T c [8]. However, the electronic system in cuprates is not strictly two-dimensional. This has been demonstrated by observation of bonding-antibonding bilayer splitting of electronic bands [9]. Indications for coherent transport were obtained in strong magnetic fields [10]. Since the two dimensional superconductivity is suppressed by fluctuations [11], presence or absence of the coherent metallic transport in the c-axis direction, i.e., in the third dimension, and the mechanism of interlayer coupling remain to be important issues for understanding high temperature superconductivity.The intrinsic Josephson effect provides an accurate way of probing weak interlayer coupling in cuprates. Due to a d-wave symmetry of the order parameter, the product of the Josephson critical current I c and the normal resistance R n in intrinsic junctions should strongly depend on the coherence (momentum conservation) upon tunneling. The I c R n is maximum ∼ ∆/e for coherent, and zero for completely incoherent tunneling [12]. Here ∆ is the maximum value of the superconducting energy gap. Analysis of I c R n in intrinsic Josephson junctions indicated that in overdoped Bi-2212 interlayer tunneling is predominantly coherent I c R n ∼ ∆/e [13,14]. However, eI c R n /∆ rapidly decreases upon opening of the pseudogap in the underdoped state [13,14]. This may either * Electronic address: Vladimir.Krasnov@fysik.su.se indicate that interlayer tunneling becomes progressively more incoherent with decreasing doping [13], or that the Fermi surface i...

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Coherent generation of phonon-polaritons in Bi2Sr2CaCu

Cited by 21 publications

References 30 publications

Persistent electrical doping of Bi2Sr2CaCu2O
Motzkau
¹
,
Jacobs
²
,
Katterwe
³

et al. 2012
Phys. Rev. B
Self Cite
13
1
10
0
View full text Add to dashboard Cite

Persistent electrical doping of Bi2Sr2CaCu2O
Motzkau
¹
,
Jacobs
²
,
Katterwe
³

et al. 2012
Phys. Rev. B
Self Cite
13
1
10
0
View full text Add to dashboard Cite

High bias anomaly in YBa2Cu3O7−x/LaMnO
Golod
¹
,
Rydh
²
,
Krasnov
³

et al. 2013
Phys. Rev. B
28
4
29
0
View full text Add to dashboard Cite

Observation of a subharmonic gap singularity in interlayer tunneling characteristics ofBi2Sr2CaCu2O8+δ

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Coherent generation of phonon-polaritons in Bi2Sr2CaCu

Cited by 21 publications

References 30 publications

Persistent electrical doping of Bi2Sr2CaCu2OMotzkau1, Jacobs2, Katterwe3 et al. 2012Phys. Rev. BSelf Cite131100View full textAdd to dashboardCite

Persistent electrical doping of Bi2Sr2CaCu2OMotzkau1, Jacobs2, Katterwe3 et al. 2012Phys. Rev. BSelf Cite131100View full textAdd to dashboardCite

High bias anomaly in YBa2Cu3O7−x/LaMnOGolod1, Rydh2, Krasnov3 et al. 2013Phys. Rev. B284290View full textAdd to dashboardCite

Observation of a subharmonic gap singularity in interlayer tunneling characteristics ofBi2Sr2CaCu2O8+δ

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Persistent electrical doping of Bi2Sr2CaCu2O
Motzkau
¹
,
Jacobs
²
,
Katterwe
³

et al. 2012
Phys. Rev. B
Self Cite
13
1
10
0
View full text Add to dashboard Cite

Persistent electrical doping of Bi2Sr2CaCu2O
Motzkau
¹
,
Jacobs
²
,
Katterwe
³

et al. 2012
Phys. Rev. B
Self Cite
13
1
10
0
View full text Add to dashboard Cite

High bias anomaly in YBa2Cu3O7−x/LaMnO
Golod
¹
,
Rydh
²
,
Krasnov
³

et al. 2013
Phys. Rev. B
28
4
29
0
View full text Add to dashboard Cite