scholarly journals Nonreciprocal transport in gate-induced polar superconductor SrTiO3

2020 ◽  
Vol 6 (13) ◽  
pp. eaay9120 ◽  
Author(s):  
Yuki M. Itahashi ◽  
Toshiya Ideue ◽  
Yu Saito ◽  
Sunao Shimizu ◽  
Takumi Ouchi ◽  
...  
Keyword(s):  
Quantum Transport ◽  
Time Reversal ◽  
Microscopic Theory ◽  
Orbit Interaction ◽  
Inversion Symmetry ◽  
Critical Temperatures ◽  
Rectification Effect ◽  
Inversion Time ◽  
Crossover Behavior ◽  
Polar Symmetry

Polar conductors/superconductors with Rashba-type spin-orbit interaction are potential material platforms for quantum transport and spintronic functionalities. One of their inherent properties is the nonreciprocal transport, where the rightward and leftward currents become inequivalent, reflecting spatial inversion/time-reversal symmetry breaking. Such a rectification effect originating from the polar symmetry has been recently observed at interfaces or bulk Rashba semiconductors, while its mechanism in a polar superconductor remains elusive. Here, we report the nonreciprocal transport in gate-induced two-dimensional superconductor SrTiO3, which is a Rashba superconductor candidate. In addition to the gigantic enhancement of nonreciprocal signals in the superconducting fluctuation region, we found kink and sharp peak structures around critical temperatures, which reflect the crossover behavior from the paraconductivity origin to the vortex origin, based on a microscopic theory. The present result proves that the nonreciprocal transport is a powerful tool for investigating the interfacial/polar superconductors without inversion symmetry, where rich exotic features are theoretically prognosticated.

Microscopic theory of diffusive spin current with spin-orbit interaction

2011 ◽  
Vol 83 (14) ◽  
Author(s):  
Kazuhiro Hosono ◽  
Akinobu Yamaguchi ◽  
Yukio Nozaki ◽  
Gen Tatara
Keyword(s):  
Spin Current ◽  
Microscopic Theory ◽  
Orbit Interaction ◽  
Spin Orbit ◽  
Spin Orbit Interaction

scholarly journals Nonreciprocal thermal transport in a multiferroic helimagnet

2020 ◽  
Vol 6 (40) ◽  
pp. eabd3703
Author(s):  
Yuji Hirokane ◽  
Yoichi Nii ◽  
Hidetoshi Masuda ◽  
Yoshinori Onose
Keyword(s):  
Symmetry Breaking ◽  
Time Reversal ◽  
Thermal Transport ◽  
Condensed Matter ◽  
Electric Polarization ◽  
Time Reversal Symmetry ◽  
Inversion Symmetry ◽  
Vector Product ◽  
Thermal Rectification ◽  
Longitudinal Thermal Conductivity

Breaking of spatial inversion symmetry induces unique phenomena in condensed matter. In particular, by combining this symmetry with magnetic fields or another type of time-reversal symmetry breaking, noncentrosymmetric materials can be made to exhibit nonreciprocal responses, which are responses that differ for rightward and leftward stimuli. However, the effect of spatial inversion symmetry breaking on thermal transport in uniform media remains to be elucidated. Here, we show nonreciprocal thermal transport in the multiferroic helimagnet TbMnO3. The longitudinal thermal conductivity depends on whether the thermal current is parallel or antiparallel to the vector product of the electric polarization and magnetization. This phenomenon is thermal rectification that is controllable with external fields in a uniform crystal. This discovery may pave the way to thermal diodes with controllability and scalability.

scholarly journals Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4

Science ◽  
2020 ◽  
Vol 367 (6480) ◽  
pp. 895-900 ◽  
Author(s):  
Yujun Deng ◽  
Yijun Yu ◽  
Meng Zhu Shi ◽  
Zhongxun Guo ◽  
Zihan Xu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Transport ◽  
Topological Insulator ◽  
Time Reversal ◽  
Magnetic Order ◽  
Anomalous Hall Effect ◽  
Time Reversal Symmetry ◽  
Zero Field ◽  
Exotic States ◽  
Ferromagnetic Layers

In a magnetic topological insulator, nontrivial band topology combines with magnetic order to produce exotic states of matter, such as quantum anomalous Hall (QAH) insulators and axion insulators. In this work, we probe quantum transport in MnBi2Te4 thin flakes—a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple antiparallel to each other; atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has an odd number of septuple layers. We observe a zero-field QAH effect in a five–septuple-layer specimen at 1.4 kelvin, and an external magnetic field further raises the quantization temperature to 6.5 kelvin by aligning all layers ferromagnetically. The results establish MnBi2Te4 as an ideal arena for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.

REPRESENTATION OF SPACE INVERSION, TIME REVERSAL, AND PARTICLE CONJUGATION IN QUANTUM FIELD THEORY

1961 ◽  
Vol 39 (1) ◽  
pp. 22-34 ◽  
Author(s):  
F. A. Kaempffer
Keyword(s):  
Time Reversal ◽  
Bilinear Forms ◽  
Fermion Field ◽  
Unitary Operators ◽  
Inversion Time ◽  
Direct Sum ◽  
Representation Of Space ◽  
Antiunitary Operator ◽  
Symmetry Operations ◽  
Space Inversion

The unitary operators of space inversion and particle conjugation and the unitary factor of the antiunitary operator of time reversal can each be written in the form eiΩ, where Ω is the direct sum of two terms, Q = Ω1θ1 + Ω2θ2, with Ω1, Ω2 Hermitean bilinear forms in the creation and annihilation operators of the boson or fermion field under consideration, and θ1 θ2 singular operators which separate the appropriate half spaces needed for the formulation of the symmetry operations. Explicit expressions are given for the generators Ω in case of a non-Hermitean boson field of spin 0, and in case of a four-component fermion field of spin [Formula: see text].

scholarly journals Electrically and magnetically switchable nonlinear photocurrent in РТ-symmetric magnetic topological quantum materials

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Hua Wang ◽  
Xiaofeng Qian
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Time Reversal ◽  
Magnetic Transition ◽  
Microscopic Theory ◽  
Zeeman Splitting ◽  
Magnetic Structures ◽  
Topological Quantum ◽  
Frequency Regime ◽  
Quantum Materials

AbstractNonlinear photocurrent in time-reversal invariant noncentrosymmetric systems such as ferroelectric semimetals sparked tremendous interest of utilizing nonlinear optics to characterize condensed matter with exotic phases. Here we provide a microscopic theory of two types of second-order nonlinear direct photocurrents, magnetic shift photocurrent (MSC) and magnetic injection photocurrent (MIC), as the counterparts of normal shift current (NSC) and normal injection current (NIC) in time-reversal symmetry and inversion symmetry broken systems. We show that MSC is mainly governed by shift vector and interband Berry curvature, and MIC is dominated by absorption strength and asymmetry of the group velocity difference at time-reversed ±k points. Taking $${\cal{P}}{\cal{T}}$$ P T -symmetric magnetic topological quantum material bilayer antiferromagnetic (AFM) MnBi2Te4 as an example, we predict the presence of large MIC in the terahertz (THz) frequency regime which can be switched between two AFM states with time-reversed spin orderings upon magnetic transition. In addition, external electric field breaks $${\cal{P}}{\cal{T}}$$ P T symmetry and enables large NSC response in bilayer AFM MnBi2Te4, which can be switched by external electric field. Remarkably, both MIC and NSC are highly tunable under varying electric field due to the field-induced large Rashba and Zeeman splitting, resulting in large nonlinear photocurrent response down to a few THz regime, suggesting bilayer AFM-z MnBi2Te4 as a tunable platform with rich THz and magneto-optoelectronic applications. Our results reveal that nonlinear photocurrent responses governed by NSC, NIC, MSC, and MIC provide a powerful tool for deciphering magnetic structures and interactions which could be particularly fruitful for probing and understanding magnetic topological quantum materials.

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