scholarly journals Visualization of superparamagnetic dynamics in magnetic topological insulators

2015 ◽  
Vol 1 (10) ◽  
pp. e1500740 ◽  
Author(s):  
Ella O. Lachman ◽  
Andrea F. Young ◽  
Anthony Richardella ◽  
Jo Cuppens ◽  
H. R. Naren ◽  
...  
Keyword(s):  
Phase Transition ◽  
Time Reversal ◽  
Quantum Interference ◽  
Topological Insulators ◽  
Quantum Phase Transitions ◽  
Electronic System ◽  
Characteristic Size ◽  
Quantum Phase ◽  
Time Reversal Symmetry ◽  
Hall Conductance

Quantized Hall conductance is a generic feature of two-dimensional electronic systems with broken time reversal symmetry. In the quantum anomalous Hall state recently discovered in magnetic topological insulators, time reversal symmetry is believed to be broken by long-range ferromagnetic order, with quantized resistance observed even at zero external magnetic field. We use scanning nanoSQUID (nano–superconducting quantum interference device) magnetic imaging to provide a direct visualization of the dynamics of the quantum phase transition between the two anomalous Hall plateaus in a Cr-doped (Bi,Sb)2Te3 thin film. Contrary to naive expectations based on macroscopic magnetometry, our measurements reveal a superparamagnetic state formed by weakly interacting magnetic domains with a characteristic size of a few tens of nanometers. The magnetic phase transition occurs through random reversals of these local moments, which drive the electronic Hall plateau transition. Surprisingly, we find that the electronic system can, in turn, drive the dynamics of the magnetic system, revealing a subtle interplay between the two coupled quantum phase transitions.

scholarly journals Topological quantum phase transition from mirror to time reversal symmetry protected topological insulator

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Partha S. Mandal ◽  
Gunther Springholz ◽  
Valentine V. Volobuev ◽  
Ondrej Caha ◽  
Andrei Varykhalov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Topological Insulator ◽  
Quantum Phase Transition ◽  
Time Reversal ◽  
Quantum Phase ◽  
Time Reversal Symmetry ◽  
Topological Quantum ◽  
Symmetry Protected

scholarly journals Energy dissipation and fluctuations in a driven liquid

2018 ◽  
Vol 115 (14) ◽  
pp. 3569-3574 ◽  
Author(s):  
Clara del Junco ◽  
Laura Tociu ◽  
Suriyanarayanan Vaikuntanathan
Keyword(s):  
Phase Transition ◽  
Steady State ◽  
Time Reversal ◽  
Time Dependent ◽  
Time Reversal Symmetry ◽  
Nonequilibrium Systems ◽  
Minimal Models ◽  
Stochastic Thermodynamics ◽  
Periodic Steady State ◽  
Time Periodic

Minimal models of active and driven particles have recently been used to elucidate many properties of nonequilibrium systems. However, the relation between energy consumption and changes in the structure and transport properties of these nonequilibrium materials remains to be explored. We explore this relation in a minimal model of a driven liquid that settles into a time periodic steady state. Using concepts from stochastic thermodynamics and liquid state theories, we show how the work performed on the system by various nonconservative, time-dependent forces—this quantifies a violation of time reversal symmetry—modifies the structural, transport, and phase transition properties of the driven liquid.

scholarly journals NV-center-based digital quantum simulation of a quantum phase transition in topological insulators

2014 ◽  
Vol 89 (4) ◽  
Author(s):  
Chenyong Ju ◽  
Chao Lei ◽  
Xiangkun Xu ◽  
Dimitrie Culcer ◽  
Zhenyu Zhang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Topological Insulators ◽  
Quantum Simulation ◽  
Quantum Phase ◽  
Nv Center

Topology-Driven Magnetic Quantum Phase Transition in Topological Insulators

Science ◽  
2013 ◽  
Vol 339 (6127) ◽  
pp. 1582-1586 ◽  
Author(s):  
J. Zhang ◽  
C.-Z. Chang ◽  
P. Tang ◽  
Z. Zhang ◽  
X. Feng ◽  
...  
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Topological Insulators ◽  
Quantum Phase

scholarly journals SCALING OF VON NEUMANN ENTROPY AT THE ANDERSON TRANSITION

2010 ◽  
Vol 24 (12n13) ◽  
pp. 1823-1840 ◽  
Author(s):  
Sudip Chakravarty
Keyword(s):  
Phase Transition ◽  
Wave Function ◽  
Phase Transitions ◽  
Ground State ◽  
Quantum Phase Transitions ◽  
Quantum Phase ◽  
Tuning Parameter ◽  
Von Neumann Entropy ◽  
Von Neumann ◽  
Anderson Transition

Extensive body of work has shown that for the model of a non-interacting electron in a random potential there is a quantum critical point for dimensions greater than two — a metal–insulator transition. This model also plays an important role in the plateau-to-plateu transition in the integer quantum Hall effect, which is also correctly captured by a scaling theory. Yet, in neither of these cases the ground state energy shows any non-analyticity as a function of a suitable tuning parameter, typically considered to be a hallmark of a quantum phase transition, similar to the non-analyticity of the free energy in a classical phase transition. Here we show that von Neumann entropy (entanglement entropy) is non-analytic at these phase transitions and can track the fundamental changes in the internal correlations of the ground state wave function. In particular, it summarizes the spatially wildly fluctuating intensities of the wave function close to the criticality of the Anderson transition. It is likely that all quantum phase transitions can be similarly described.

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