Valleytronics.com - The Valleytronics Experts

A global team of researchers observed a new microscopic mechanism enabling precise control of the magneto-optical properties of excitons in alloys of 2D semiconductors

Ron Mertens — Wed, 25 Feb 2026 10:42:08 +0200

A global team of researchers have observed a new microscopic mechanism enabling precise control of the magneto-optical properties of excitons in alloys of 2D semiconductors, potentially enabling new valleytronics applications.

As part of this study, high-quality monolayers of mixed alloys MoxW1-xSe2 with precisely controlled chemical composition were investigated. The samples were synthesized in the Czech Republic and encapsulated between flakes of hexagonal boron nitride fabricated in Japan. For a series of samples with varying molybdenum and tungsten content, systematic photoluminescence measurements were carried out at a temperature of 10 kelvin and in strong magnetic fields reaching up to 30 tesla at the Laboratoire National des Champs Magnétiques Intenses in Grenoble. An analysis of the emitted light in circular polarizations enabled highly accurate determination of the neutral exciton g-factor.

Researchers develop a new simple method to control and read quantum valley states in 2D semiconductors

Ron Mertens — Tue, 16 Dec 2025 14:02:17 +0200

Researchers at IIT Bombay developed a simple method that uses a single linearly polarized laser pulse with a slight skew to control and read quantum valley states in ultra-thin 2D semiconductors.

The researchers say that current techniques to control the quantum valley state required complex laser setups using circularly polarized light and multiple laser pulses. On top of that, the control was often incomplete or hard to measure. This means that reliable and reversible switching between the two valley states remained a major challenge. The team has now shown that a single linearly polarized laser pulse can both control and read the valley state of electrons.

Researchers directly observe dark excitons in TMDs for the first time

Ron Mertens — Sat, 27 Sep 2025 10:38:48 +0300

Researchers at the Okinawa Institute of Science and Technology (OIST) have managed to directly observe dark excitons in TMD 2D materials for the first, which may be a first step towards the use of this phenomena in valleytronics devices.

The researchers believe that dark excitons have great potential as information carriers, because they are inherently less likely to interact with light, and hence less prone to degradation of their quantum properties. On the other hand, this this invisibility also makes them very challenging to study and manipulate. The researchers now believe they have opened a route to the creation, observation, and manipulation of dark excitons.

Researchers develop a new method to create monolayer Sns, an excellent spin valleytronics material

Ron Mertens — Sun, 15 Jun 2025 07:40:58 +0300

Researchers from Tohoku University, the National Institutes for Quantum Science and Technology (QST), and Cambridge University have managed to create a monolayer tin sulfide (SnS) material, which could be suitable for spin-valleytronics applications.

The researchers explain that SnS is special because it can conduct electricity and respond to light in unique ways. But io far it has been challenging to selectively form SnS from base tin (Sn) and sulfur (S) - sometimes other materials are produced instead, such as SnS2 instead. Now the researchers developed an easier and safer process that can reliably produce entire sheets of SnS.

Researchers use graphene to create valley-polarized current

Ron Mertens — Sat, 19 Oct 2024 10:59:54 +0300

Researchers from Delft University of Technology demonstrated a device that generates electrical currents with a precisely controlled number of electrons at each valley. The researchers say that when electrons are squeezed through a narrow channel, they emerge as two jets which are valley polarized. By steering these jets with a magnetic field, the researchers can regulate which jet enters through a second opening, gaining control on how many electrons end up in a specific valley.

The researchers, led by Josep Ingla-Aynes, based their device on bi-layer graphene.

Researchers demonstrate the direct coupling of light to valley current

Ron Mertens — Sun, 01 Sep 2024 14:36:10 +0300

Researchers from the Max Born and Max Planck institutes have shown that the few cycle limit of circularly polarized light is imbued with an emergent vectorial character that allows direct coupling to the valley current. The underlying physical mechanism involves the emergence of a momentum space valley dipole, the orientation and magnitude of which allows complete control over the direction and magnitude of the valley current.

The researchers demonstrate this effect via minimal tight-binding models both for the visible spectrum gaps of the transition metal dichalcogenides as well as the infrared gaps of biased bilayer graphene.

Researchers discover ferro-valleytricity in five-layer graphene

Ron Mertens — Fri, 20 Oct 2023 13:36:30 +0300

Researchers from MIT, Harvard and Japan's NIMS have discovered that in a five-layer graphene arranged in a rhombohedral pattern, a rare state occus, a multi-ferroic state, in which the material exhibits both unconventional magnetism and an exotic type of electronic behavior, which the team has named "ferro-valleytricity".

The first time that ferro-valleytricity and unconventional magnetism are observed, in five layers of graphene. This is not occurring in single-layer graphene (or in two, three, or four layers). This state could lead to a future valleytronics device, a fast storage device that will be highly efficient, as the domains in such a device can be switched very fast with a very low-power electric field.

Researchers use perovskites and 2D TMDs to create a promising valleytronics material

Ron Mertens — Sun, 10 Sep 2023 09:20:21 +0300

Researchers from the US DOE Brookhaven National Laboratory, together with Northrop Grumman, have found a way to maintain valley polarization at room temperature using novel materials and techniques.

The researchers used a chiral lead halide perovskite material (R/S-NEAPbI3). The researchers layered 500 nanometer thick flakes onto a monolayer molybdenum disulfide (MoS2), to create what is known as a heterostructure. Using a linearly polarized laser to excite the heterostructure the researchers fabricated and then measured the light that was emitted from the molybdenum disulfide TMD using a confocal microscope. They have discovered that the new material is promising for valletronics applications.

Researchers show that Platinum diselenide is a promising 2D material for terahertz valleytronics

Ron Mertens — Thu, 07 Sep 2023 16:59:38 +0300

Researchers from CNRS in France demonstrated that Platinum diselenide (PtSe₂) is a promising 2D material for a terahertz (THz) range valleytronics device.

The researchers explain that PtSe₂ is promising as, unlike other transition metal dichalcogenides (TMDs), its bandgap can be uniquely tuned from a semiconductor in the near-infrared to a semimetal with the number of atomic layers. This gives the material unique THz photonic properties that can be layer-engineered. In this research, the main demonstration was that a controlled THz nonlinearity - tuned from monolayer to bulk - can be realized in wafer size polycrystalline through the generation of ultrafast photocurrents and the engineering of the bandstructure valleys.

Researchers discover giant valley-selective Ising coupling in the surface layer of an intercalated transition metal

Ron Mertens — Thu, 23 Feb 2023 15:23:41 +0200

An international team of scientists led by a group at the University of St Andrews and the University of Manchester, report on a giant valley-selective Ising coupling in the surface layer of an intercalated transition metal dichalcogenide, V_1/3NbS₂.

Using angle-resolved photoemission spectroscopy measurements, the researchers proved the surface electronic structure of the semimetal. The researchers discovered an alternating pattern of enhancement and quenching of valley-spin polarization of the host NbS2 layers due to the intercalated Vanadium ions, equivalent to the application of a 250 T magnetic field. The researchers say that this is a major step forward in valleytronics, opening up new opportunities for the development of advanced electronic devices.

Researchers develop a trilayer TMD heterostructure with interlayer excitons

Ron Mertens — Wed, 29 Jun 2022 21:00:08 +0300

Researchers from China's Tsinghua University developed a novel material, made from a stack of 2D materials, that offers interlayer excitons, useful for valleytronics applications.

The new material is a trilayer TMD heterostructure, composed of molybdenum and sulfur, molybdenum and selenium, and tungsten and selenium. Using photoluminescence spectroscopy, the researchers confirmed the presence of interlayer excitons and described various properties and requirements of the phenomenon.

Researchers developed an approach to align Landau levels of different valleys in 2D materials

Ron Mertens — Thu, 16 Jun 2022 15:28:02 +0300

Researchers from the National University of Singapore researchers have developed an approach to account for the effect of dynamical electron-electron interactions when predicting the energy levels in valleytronic materials in the presence of a magnetic field.

The researchers predicted that Landau levels belonging to different valleys in a two-dimensional (2D) valleytronic material, monolayer tungsten diselenide (WSe₂), can be aligned at a critical magnetic field. The alignment of distinct entities, such as two laser beams, or two pillars, is a common goal in many fields of science and engineering. In the more exotic world of quantum mechanics, the alignment of quantized electronic levels can enable the creation of particles called pseudo-spinors that are useful for quantum computing applications.

IIT Bombay researchers developed a valley polariser based on 2-D Xenes

Ron Mertens — Thu, 19 May 2022 18:55:15 +0300

Researchers from the Indian Institute of Technology Bombay (IIT Bombay) have proposed a device structure for a valley polariser which is robust, all-electrical, and can be seamlessly integrated with modern electronics. The device can be fabricated using existing fabrication techniques.

The device is based on 2D-Xene materials. A single-layer of 2-D Xene is used as the charge carrying channel. A terminal called a gate controls the electric current flowing through the channel, similar to how a gate controls the current in the modern transistor design. The gate structure, which is also used to create the valley separation, sandwiches the 2-D Xene ribbon.

Graphene grown on curved surfaces could enable Valleytronics devices

Ron Mertens — Sun, 03 Apr 2022 08:46:56 +0300

Researchers from Rice University suggest that growing graphene sheets on curved surface may be a useful technique to create valleytronics devices.

The peaks and valleys in the resulting "deformed" graphene sheet would create channels that will feature small magnetic fields. It will also be a way to achieve a Hall Effect, useful for valleytronics devices.

Researchers manage to emit laser-light from thin structure at room temperature, could enable future valleytronics devices

Ron Mertens — Tue, 14 Dec 2021 11:27:34 +0200

Researchers from the University of Oldenburg, managed to create a three-atoms-thick structure that emits laser-like light, at room temperature, for the first time. The researchers believe that coherent light emission from ultathin crystals could enable valleytronics devices in the future.

To create the light, the researchers used exciton-polaritons particles, formed from the strong interaction between confined photons and electrons. The structure itself is made from a single-layer of a WSe₂ crystal, that sits on top of a hBN 2D layer. The idea is that the exciton-polaritons are created in a trap in the WSe₂ and then captured and reflected by two distributed Bragg reflectors (DBRs) that act as mirrors.

Researchers show it is possible to realize a valleytronics device in pristine graphene

Ron Mertens — Mon, 19 Jul 2021 11:55:13 +0300

Researchers from Germany (Max-Born Institute) and India (IIT Bombay) have shown that it is possible to realize a valleytronics device in pristine graphene.

Graphene (and other graphene-like systems) feature an extra degree of electron freedom, or valley pseudo-spin. This has interesting potential in valleytronics applications, but the implementation of valleytronics ideas has been so far limited to gapped graphene-like semiconducting 2D materials, most commonly transition metal dichalcogenides, and has never been attempted in pristine graphene, because graphene monolayers have zero bandgap, zero Berry curvature, and thus nearly identical valleys,.

Researchers demonstrate how few-cycle linearly polarized pulses can induce a high degree of valley polarization

Ron Mertens — Fri, 26 Feb 2021 11:06:54 +0200

Scientists from several research institutes in Germany and the UK have demonstrated that few-cycle linearly polarized pulses can induce a high degree of valley polarization.

The mechanism to induce such polarization does not rely on the optical selection rules, and therefore can be in principle used in inversion symmetric materials, such as TMD bilayers or graphene. This could enable the design of ultrafast valleytronic devices.

Researchers have demonstrated electrical valley control in 3D dual-gate diamond field-eﬀect transistors

Ron Mertens — Sun, 21 Feb 2021 07:53:28 +0200

Researchers from Sweden's Uppsala university and from UK's Element Six have demonstrated electrical valley control in 3D dual-gate diamond field-effect transistors.

The team has fabricated valley transistors on single-crystalline diamond plates with ultra-low nitrogen impurity concentrations. A dual-gate configuration was used to gain a high degree of freedom of the control of the valley currents. The control of location and time of the valley-polarized currents was achieved by adding multiple drain electrodes.

Researchers use rotated graphene between a ferromagnetic insulator to generate valley-only states

Ron Mertens — Fri, 05 Feb 2021 18:01:57 +0200

Researchers from ETH Zurich and Aalto University showed that sandwiching two slightly rotated layers of graphene between a ferromagnetic insulator provides a unique setting for new electronic states.

The combination of ferromagnets, graphene's twist engineering, and relativistic effects force the "valley" property to dominate the electrons behavior in the material. In particular, the researchers showed how these valley-only states can be tuned electrically, providing a materials platform in which valley-only states can be generated.

A 2D derivative of perovskite could hold the key for future valleytronics devices

Ron Mertens — Tue, 27 Oct 2020 13:33:26 +0200

Researchers from Rice University and Texas A&M University have discovered that a 2D derivative of perovskite has a good potential for valleytronics applications.

The researchers synthesized a layered compound of cesium, bismuth and iodine that is able to store the valley states of electrons, but only in the structure's odd layers. These bits can be set with polarized light, and the even layers appear to protect the odd ones from the kind of field interference that bedevils other perovskites, according to the researchers.

Cornell researchers show how to control the valley of electrons using electrical inputs

Ron Mertens — Fri, 16 Oct 2020 15:10:37 +0300

Researchers from Cornell University managed to control the valley (orbital angular momentum) of electrons in a material by using electrical inputs to manipulate the magnetism of an adjacent material.

The device is built from a 2D tungsten diselenide (WSe₂), a material whose energy landscape has valleys, atop a few atomic layers of chromium triiodide ( CrI₃), a material whose magnetism can be electrically altered. The researchers are now looking for an alternative electrically-controlled magnetism material that will behave in a similar way at room temperatures.

They then changed the voltage across the CrI3 layers and measured the population of the WSe2 valleys using a technique that monitored the spin direction of light that the WSe2 emitted when illuminated by a laser. They found that the direction changed when the voltage was applied, indicating a switch in the semiconductorâs filled valley. The CrI3 layer is magnetic only at around 60 K, so the team says that their next step is to find a material that would allow valley sorting at room temperature.

Researchers report of effective valley separation in TMDCs by using PhCs

Ron Mertens — Tue, 25 Aug 2020 14:47:06 +0300

Researchers from Fusain University and the Chinese National University of Defense Technology demonstrated that 2D all-dielectric PhC slabs without in-plane inversion symmetry can be used to efficiently separate valley exciton emission of a 2D WS2 monolayer in the far field at room temperature.

Left: PhC slabs with C4 symmetry and without in-plane inversion symmetry. By breaking the in-plane inversion symmetry, the polarization states of PhC can cover entire PoincarÃ© sphere's two poles. Right: Illustration of photoluminescence of WS2 monolayer on the PhC slab without in-plane inversion symmetry.

This is the first report of effective valley separation in TMDCs by using PhCs. This method could be extended to manipulate valley exciton emission of other TMDCs monolayers. The ability of this PhC slabs to transport valley information from the near field to the far field would help to develop photonic devices based on valleytronics.

Researchers observe light emission from intervalley excitons for the first time

Ron Mertens — Sat, 16 May 2020 15:30:56 +0300

Researchers from the University of California, Riverside, has observed light emission intervalley transmissions. The researchers say that this light emission can be used to read valley information from Valleytronics devices in the future.

The researhers observed the phenomenon in monolayer tungsten diselenide (WSe2) - a promising valleytronic material that possesses two valleys with opposite dynamic characteristics in the band structure, and can interact strongly with light.

Researchers use a silver sawtooth nanoslit array to produce valley-coherent photoluminescence

Ron Mertens — Sun, 16 Feb 2020 09:06:34 +0200

Researchers from the University of Groningen managed to produce valley-coherent photoluminescence at room temperatures - by using a silver sawatooth nanoslit array in two-dimensional tungsten disulfide flakes.

So-called "coherent light" can be used to store or transfer information in quantum electronics, and the researchers say that their plasmon-exciton hybrid device model may be promising for future integrated nanophotonics applications.

Researchers develop a method to read the valley indices of dark excitons and trions

Ron Mertens — Thu, 31 Oct 2019 15:38:09 +0200

Researchers from the University of California, Riverside,have developed a new method to read the valley indices of the dark excitons and trions. The researchers used monolayer (2D) tungsten diselenide (WSe2), a semiconductor with two distinct electronic valleys.The material hosts bright and dark excitons or trions with different spin configurations.

The researchers say that dark excitons and trions in monolayer WSe2 have much longer lifetime and better valley stability than the common bright excitons and trions - which makes them excellent candidates for valleytronic applications. But up until now there was no method to read the valley indices of the dark excitons and trions because their light emission from either valley has exactly the same energy and polarization. By identifying a measurable physical quantity that can distinguish the two valley indices of dark excitons and trions, the team was able to devise a method to read the valley indices.

Stephan Roche from ICREA and CINN discusses valleytronics in 2D materials

Ron Mertens — Mon, 21 Oct 2019 15:27:07 +0300

The International Institute of Physics in Brazil recently uploaded this interesting talk by Stephan Roche from the ICREA and CINN who discusses valleytronics in 2D materials (such as graphene):

This talk was given as part of the IIP's 2D Materials: From Fundamentals to Spintronics workshop which took place in early October.

Researchers discover the formation of valley domain, potentially expand valleytronics technology

Ron Mertens — Thu, 25 Jul 2019 21:38:09 +0300

Researchers from Korea's Daegu Gyeongbuk Institute of Science and Technology (DGIST) discovered the formation of valley domain, which can expand valleytronics technology.

The researchers say that they have solved the stability problem inherent in valley spin in valleytronics devices by discovering the formation of valley domain in 2D molybdenum disulfide (MoS2). The team identified that a valley domain formed in an extreme nano structure can be used to store information in place of spin.

EPFL researchers developed a new to manipulate excitons valleys

Ron Mertens — Sun, 06 Jan 2019 09:12:31 +0200

Researchers from EPFL's Laboratory of Nanoscale Electronics and Structures (LANES) developed a new way to control the valley properties of excitons and change the polarization of the light they generate.

Excitons, or electron and electron hole pairs, are created when an electron absorbs light and moves into a higher energy band. To research the excitons, the researchers used a material made from tungsten diselenide (WSe2) and molybdenum diselenide (MoSe2), and a circular polarized laser that was focused on the film.

Researchers develop a graphene-based topological valley valve

Ron Mertens — Wed, 12 Dec 2018 10:45:06 +0200

Researchers from Penn State University developed a topological valley valve, which controls electron flow. Using electron "beam splitters", the researchers achieved high-level of electron control.

Using bilayer graphene, the researcher created electron waveguides created by gates defined with extreme precision using state-of-the-art electron beam lithography.By controlling the topology of the waveguides (the valley-momentum locking of the electrons), the researchers can control electron flow.

The US NSF allocates $20-25 million towards material research aimed towards quantum engineering and science

Ron Mertens — Mon, 03 Sep 2018 13:42:14 +0300

The US National Science Foundation (NSF) has allocated $20-25 million for a new six year program called "Enabling Quantum Leap: Convergent Accelerated Discovery Foundries for Quantum Materials Science, Engineering, and Information" (Q-AMASE-i).

Q-AMASE-i encompasses many clases of materials, includings ones that explore the paradigms or spintronics, hybrid 2D materials - and Valleytronics.