Infinite-randomness quantum critical points induced by dissipation

Vojta, Thomas; Kotabage, Chetan; Hoyos, José A.

doi:10.1103/physrevb.79.024401

Cited by 73 publications

(92 citation statements)

References 65 publications

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“…Such unpaired electrons can originate from the dissipation effect, which gives rise to the SMT with critical 9 resistance much smaller than h/4e 237 . Subsequent theoretical investigations reveal that the quenched disorder dramatically changes the scaling behavior of SMT 38 , and result in activated scaling identical to that of the random transverse field Ising model, in which the dynamical exponent z continuously varies when approaching the quantum critical point 39 . This active scaling behavior can be regarded as the "quantum version" of Griffiths singularity, which is called quantum Griffiths singularity 40 .…”

Section: Textmentioning

confidence: 99%

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

et al. 2017

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KEYWORDS: NbSe 2 , transition-metal dichalcogenides, macro-size monolayer film, ultralow temperature and high magnetic field electrical transport, Ising superconductivity, quantum phase transition 2 ABSTRACT Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics and quantum computing devices. The mechanical exfoliation technique of micro-size TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large area and high quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe 2 films on bilayer graphene terminated surface of 6H-SiC(0001) substrates by molecular beam epitaxy (MBE) method. The films exhibit an onset superconducting critical transition temperature (T c onset ) above 6 K, 2 times higher than that of mechanical exfoliated NbSe 2 flakes. Simultaneously, the transport measurements at high magnetic fields reveal that the parallel characteristic field B c// is at least 4.5 times higher than the paramagnetic limiting field, consistent with Zeeman-protected Ising superconductivity mechanism. Besides, by ultralow temperature electrical transport measurements, the monolayer NbSe 2 film shows the signature of quantum Griffiths singularity when approaching the zero-temperature quantum critical point. TEXTQuasi-2D superconductors such as ultrathin films with thickness down to monolayer [1][2][3][4][5][6][7] 10, 11,13 , the coexistence of charge density wave (CDW) and the superconducting phase was observed down to the monolayer limit but the T c of monolayer NbSe 2 got significantly suppressed (less than 3.1 K) compared with its bulk value (7.2 K).Superconductor-insulator (metal) transition (SIT/SMT), a paradigm of quantum phase transition, is an important topic in condensed matter physics. In the 2D limit regime, the orbital effect is restricted in parallel magnetic field. Calculations show that in anisotropic superconductors, the FFLO state might lead to an enhancement of the upper critical field between 1.5 and 2.5 times of the Pauli paramagnetic limit field 32,35 . In perpendicular magnetic field cases, the characteristic field B c (0) of NbSe 2 film is estimated to be 2.87 T, smaller than the Pauli paramagnetic limit field (8.21 T). Besides, the 8 Maki parameter α⊥ = 0.44 is smaller than 1.8. In parallel magnetic field cases, the characteristic field B c// (0) ~ 37.22 T is at least 4.5 times of Pauli paramagnetic limit field, which exceeds the theoretical predictions of 1.5 ~ 2.5 times 32,35 . Therefore, the chance of the existence of FFLO state in monolayer NbSe 2 is little.The sample 3 (with T c onset ~ 6 K, Figure S5 For SIT, the sample critical resistance on phase transition is th...

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Section: Textmentioning

confidence: 99%

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

et al. 2017

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“…As justified in Ref. [43], the Ohmic dissipation can give rise to the quantum Griffiths singularity for quantum O(N) symmetry systems with quenched disorder, but a non-Ohmic dissipation smears the quantum Griffiths singularity. In this paper, the phase coherence length tends to saturation, but does not follow the logarithmic law as suggested by the activated scaling [42].…”

Section: Crossing Point and Quantum Griffiths Singularitymentioning

confidence: 77%

Scaling properties of the plateau transitions in the two-dimensional hole gas system

et al. 2016

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“…We therefore expect the cost of our method to scale as N y+3/2 s or N 3/2 s in the quantum Griffiths and quantum paramagnetic phases, respectively. For three dimensional systems, sparse matrices can be inverted in O(N 2 s ) operations [27], correspondingly the cost of our method is expected to behave as N A possible application of our method in three dimensions is the disordered itinerant antiferromagnetic quantum phase transitions [21,22]. The clean transition is described by a Landau-Ginzburg-Wilson theory which is generalization of the action (1) to d = 3 space dimensions and N = 3 order parameter components [18,19].…”

Section: Discussionmentioning

confidence: 99%

Numerical method for disordered quantum phase transitions in the large‐N limit

Nozadze

Vojta

2013

Physica Status Solidi (b)

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We develop an efficient numerical method to study the quantum critical behavior of disordered systems with O(N ) order-parameter symmetry in the large−N limit. It is based on the iterative solution of the large−N saddle-point equations combined with a fast algorithm for inverting the arising large sparse random matrices. As an example, we consider the superconductor-metal quantum phase transition in disordered nanowires. We study the behavior of various observables near the quantum phase transition. Our results agree with recent renormalization group predictions, i.e., the transition is governed by an infinite-randomness critical point, accompanied by quantum Griffiths singularities. In contrast to the existing numerical approach to this problem, our method gives direct access to the temperature dependencies of observables. Moreover, our algorithm is highly efficient because the numerical effort for each iteration scales linearly with the system size. This allows us to study larger systems, with up to 1024 sites, than previous methods. We also discuss generalizations to higher dimensions and other systems including the itinerant antiferromagnetic transitions in disordered metals.Copyright line will be provided by the publisher 1 Introduction Randomness can have much more dramatic effects at quantum phase transitions than at classical phase transitions because quenched disorder is perfectly correlated in the imaginary time direction which needs to be included at quantum phase transitions. Imaginary time acts as an additional coordinate with infinite extension at absolute zero temperature. Therefore, the impurities and defects are effectively very large which leads to strong-disorder phenomena including power-law quantum Griffiths singularities [1,2,3], infinite-randomness critical points characterized by exponential scaling [4,5], and smeared phase transitions [6]. For example, the zero-temperature quantum phase transition in the random transverse-field Ising model is governed by an infiniterandomness critical point [5] featuring slow activated (exponential) rather than power-law dynamical scaling. It is accompanied by quantum Griffiths singularities. This means, observables are expected to be singular not just at criticality but in a whole parameter region near the quan-

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Infinite-randomness quantum critical points induced by dissipation

Cited by 73 publications

References 65 publications

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

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

Scaling properties of the plateau transitions in the two-dimensional hole gas system

Numerical method for disordered quantum phase transitions in the large‐N limit

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Infinite-randomness quantum critical points induced by dissipation

Cited by 73 publications

References 65 publications

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

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

Scaling properties of the plateau transitions in the two-dimensional hole gas system

Numerical method for disordered quantum phase transitions in the large‐N limit

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Product

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

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